{"paper_id":"262b2012-52b2-45ac-be8e-8d8884bdae2d","body_text":"1 \n \nMultiple ShKT domain-containing MUL-1 proteins act as redox-responsive modulators of 1 \noxidative stress signaling in C. elegans 2 \n 3 \nEmilio Carranza-Garcia 1, Abe Gayle Santos 2-4, Kyoung-Hye Yoon 3, 4, Anton Gartner* 1, 5  4 \n1) Center for Genomic Integrity, Institute for Basic Science, UNIST-gil 50, Ulsan 44919, 5 \nRepublic of Korea, 6 \n2) Department of Physiology, Yonsei University Wonju College of Medicine, 20 Ilsan-ro, Wonju, 7 \nSouth Korea 8 \n3) Organelle Medicine Research Center, Yonsei University Wonju College of Medicine, 20 Ilsan-9 \nro, Wonju, South Korea 10 \n4) Department of Global Medical Science, Yonsei University Wonju College of Medicine, 20 11 \nIlsan-ro, Wonju, South Korea 12 \n5) Department for Health Science and Technology, Ulsan National Institute of Science and 13 \nTechnology (UNIST), UNIST-gil 50, Ulsan 44919, Republic of Korea. 14 \n* To whom correspondence should be addressed. Email tgartner67@gmail.com 15 \n 16 \nKeywords: C. elegans , oxidative stress, ionizing irradiation, MUL-1, ShKT domain, stress 17 \nsignaling  18 \n 19 \nAcknowledgements 20 \nWe want to thank the members of the Gartner Laboratory and the Korean Institute for Basic 21 \nScience Center for Genomic Integrity for their fruitful discussions. We especially thank Aymeric 22 \nBailly and Albena Dinkova-Kostova for prereviewing the manuscript and Ulrike Gartner for 23 \nproofreading. We thank Prof KJ Myung for his unwavering support. This work was supported by 24 \nthe Korean Institute for Basic Science (grant IBS-R022-D1-2025) and the National Research 25 \nFoundation of Korea (grant: RS-2024-00409403). Author contributions:  ECG, and AG: 26 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n2 \n \nConceptualization and writing. ECG, vast majority of reagent generation and experimental work. 27 \nAGS, and KHJ, Pseudomonas experiments.  28 \n  29 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n3 \n \nMultiple ShKT domain-containing MUL-1 proteins act as redox-responsive modulators of 30 \noxidative stress signaling in C. elegans 31 \n 32 \nAbstract  33 \nOrganismal survival depends on coordinated responses to oxidative stress and DNA damage. 34 \nUsing Caenorhabditis elegans, we investigate mul-1,  a robust transcriptional target of ionizing 35 \nradiation and reactive oxygen species. Although annotated as a mucin, MUL-1 is a small ShKT 36 \ndomain-containing protein belonging to an invertebrate expanded family of cysteine-rich 37 \nproteins. mul-1  is selectively induced by oxidative stress, including IR, hydrogen peroxide 38 \n(H2O2), Pseudomonas aeruginosa  infection, or loss of the peroxiredoxin PRDX-2, via the p38 39 \nMAPK-ATF-7 pathway in intestinal cells. Loss of mul-1 and its paralogs increases ROS 40 \naccumulation, oxidative stress sensitivity, and CEP-1/p53 dependent germ cell apoptosis. 41 \nCombined deletion of mul-1  paralogs causes constitutive apoptosis, reduced fecundity, and 42 \ncompensatory activation of DAF-16/Foxo and SKN-1/Nrf2 stress response pathways. Together 43 \nwith genetic analysis of SYSM-1, these findings suggest MUL-1-like ShKT proteins buffer 44 \noxidative stress. 45 \n 46 \nIntroduction 47 \nOrganismal survival depends on the activation of coordinated stress response pathways. 48 \nIonizing radiation (IR) and reactive oxygen species (ROS) are among the most potent inducers 49 \nof cellular stress, triggering DNA damage and oxidative insults. The nematode Caenorhabditis 50 \nelegans provides a genetically tractable model to dissect the regulation and functional impact of 51 \nthese pathways at the organismal level. Although IR can directly induce DNA strand breaks, 52 \nmost DNA damage associated with IR exposure arises indirectly through ROS generation. ROS 53 \ninclude superoxide (O 2\n-), hydrogen peroxide (H 2O2), and hydroxyl radicals (•OH), produced 54 \nwhen radiation interacts with cellular water and organic molecules (Roots & Okada, 1975; Ward, 55 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n4 \n \n1994). In addition to oxidizing bases, generating abasic sites, and causing DNA strand breaks, 56 \nROS also inflict cellular damage by oxidizing metabolites, lipids, and proteins (Dalle-Donne et 57 \nal., 2006; Yohe & Davies, 2014). ROS are also generated endogenously, for instance, through 58 \nmitochondrial electron leakage and NADPH oxidase activity (Forman et al., 2010). Among ROS, 59 \nH2O2 is a precursor to highly reactive hydroxyl radicals generated via Fenton chemistry (Forman 60 \n& Zhang, 2021; Koppenol, 1993), but can also act as a signaling molecule (Forman et al., 2010; 61 \nMiranda-Vizuete & Veal, 2017). For instance, in C. elegans, H2O2 regulates FLP-1 neuropeptide 62 \nrelease from AIY interneurons during diet-induced stress response in the gut (Jia & Sieburth, 63 \n2021), and this response is potentiated by the H 2O2-dependent release of the FLP-2 peptide 64 \nfrom the intestine (Jia et al., 2024). Elevated ROS in AWC neurons causes NLP-1 peptide 65 \nsecretion, which induces the mitochondrial unfolded protein response in the gut and reduces its 66 \ndigestive capacity (Liu et al., 2024). Cellular detoxification of H 2O2 is primarily mediated by 67 \nantioxidant enzymes such as superoxide dismutases, peroxiredoxins, and glutathione 68 \nperoxidases, which rely on conserved cysteine residues or thiol-containing cofactors for redox 69 \ncycling (Aranda-Rivera et al., 2022; Juan et al., 2021). 70 \n 71 \nTranscriptomic analyses following IR in C. elegans  revealed no induction of canonical DNA 72 \nrepair genes (Greiss et al., 2008). Among the DNA damage response genes, only the pro-73 \napoptotic BH3-only genes egl-1 and ced-13, both CEP-1/p53 targets, and required for DNA 74 \ndamage-induced germ cell apoptosis, were upregulated (Greiss et al., 2008; Schumacher et al., 75 \n2005). In contrast, a broad CEP-1/p53 independent transcriptional activation of oxidative stress-76 \nrelated and innate immunity-associated genes was observed, many of which are nematode-77 \nspecific (Greiss et al., 2008). Notably, mul-1 emerged as the most robustly IR-induced 78 \ntranscript, and its induction requires the conserved p38 MAPK pathway (Greiss et al., 2008; 79 \nKimura et al., 2012). Recently, a MUL-1 high-copy transgene was shown to be expressed in the 80 \ngut, and mul-1 deletion was associated with reduced sensitivity to Pseudomonas aeruginosa  81 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n5 \n \ninfection, possibly by limiting bacterial association with gut epithelium (Hoffman et al., 2020). 82 \nHowever, while annotated as a mucin-like gene, MUL-1 lacks some hallmark features of 83 \nvertebrate mucins, which are typically thousands of amino acids long, highly enriched in serine 84 \nand threonine, and heavily glycosylated to form gel-like protective barriers in gut epithelia 85 \n(Johansson et al., 2013). Instead, MUL-1 is a small 259-amino-acid protein composed mainly of 86 \nfive ~36-42 amino acid ShKT domains (InterPro Entry IPR003582: ShKT domain). Only a 42-87 \namino-acid unstructured region between the two C-terminal ShKT domains is highly enriched in 88 \nserine/threonine residues. ShKT domains were initially characterized as potent toxins derived 89 \nfrom sea anemones that inhibit mammalian potassium channels (Castañeda et al., 1995; Gerdol 90 \net al., 2019; Harvey & Vita, n.d.; Shafee et al., 2019; Tudor et al., 1998). Except for the human 91 \nmetalloprotease MMP23, which contains a single ShKT module, this motif is otherwise absent 92 \nfrom vertebrate proteomes (Rangaraju et al., 2010). Structurally, ShKT domains are defined by 93 \nsix conserved cysteine residues that form three disulfi de bonds, stabilizing a compact two- α -94 \nhelix fold commonly used to engage and modulate potassium channels (Castañeda et al., 1995; 95 \nShafee et al., 2019; Tudor et al., 1998). Given this distinctive organization, we posit that MUL-1 96 \nmay perform roles unrelated to, or in addition to, those of traditional mucins. 97 \n 98 \nThe identification of mul-1  as an IR-responsive gene is reminiscent of sysm-1, a small protein 99 \nalso induced by IR and composed of two ShKT domains (Soltanmohammadi et al., 2022). Like 100 \nmul-1, sysm-1 induction depends on the p38 MAPK pathway  (Soltanmohammadi et al., 2022). 101 \nFunctional studies have shown that SYSM-1 is secreted from the intestine and is required for 102 \ngerm cell apoptosis following IR, acting in parallel to the C. elegans  CEP-1/p53 pathway. 103 \nNotably, the induction of the two pro-apoptotic BH3 domain-only genes, egl-1 and ced-13  104 \nremains intact in sysm-1  mutants, suggesting that SYSM-1 conveys stress signals across 105 \ntissues, independent of CEP-1 transcriptional activity (Soltanmohammadi et al., 2022). 106 \n 107 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n6 \n \nHere, we employed a mul-1 transcriptional reporter as an inroad to dissect regulatory circuits 108 \ninvolved in the oxidative stress response. mul-1 is induced by IR, H 2O2, Pseudomonas infection 109 \nand loss of the peroxiredoxin PRDX-2. Peroxiredoxins are abundant cysteine-based peroxide 110 \nreductases that detoxify H 2O2 through the oxidation of conserved N-terminal cysteines to 111 \nsulfenic acid, followed by disulfide bond formation with a receiving cysteine (Rhee, 2016). We 112 \nfound that mul-1 expression is induced in the intestine and depends on p38 signaling and its 113 \ndownstream transcription factor, ATF-7. mul-1 mutants are hypersensitive to oxidative stress 114 \nand exhibit increased p53-dependent germ cell apoptosis upon IR. MUL-1 belongs to a family of 115 \nproteins expanded in invertebrates, and we included the three most closely related paralogs, as 116 \nwell as related sysm-1,  in our analysis. MUL-1 family quadruple mutants display a further 117 \nincrease in radiation-induced apoptosis, and excessive apoptosis occurs even in the absence of 118 \nIR. Furthermore, both mul-1 and the quadruple mutant bypass the apoptosis defect of sysm-1. 119 \nIn compound mul-1  paralog mutants and prdx-2 single mutants, compensatory DAF-16-120 \ndependent SOD-3 and SKN-1-dependent GST-4 induction occurs even in the absence of 121 \nexogenous stress. We argue that MUL-1-like proteins are part of a regulatory circuit that have a 122 \nkey role in the organismal responses to oxidative stress. We hypothesize that MUL1-like genes 123 \nmay act via their ShKT domains as scavengers or rheostats of oxidative damage. 124 \n 125 \nResults 126 \nTranscriptional regulation of mul-1 127 \nTo assess if and where mul-1 (F49F1.6) is induced upon IR, we developed a transcriptional 128 \nreporter strain, mul-1(syb3342), in which the coding sequence of mul-1 is replaced with 129 \nmCherry fused to histone H2B for fluorescent detection and nuclear targeting. Under control 130 \nconditions, the basal expression of mul-1 is predominantly localized to the nuclei of gut cells, 131 \nwith the strongest expression observed in the two anterior-most gut nuclei (Fig. 1A, C) , with 132 \nexpression gradually increasing during larval development, reaching a maximum in L4 larvae 133 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n7 \n \nand adults (Fig. 1A, C-D, black lines) . To examine the induction of mul-1 under DNA-damaging 134 \nconditions, we exposed mul-1(syb3342) animals at all larval stages to 100 Gy of IR and 135 \nanalyzed transcriptional activation 6 hours post-treatment. IR exposure results in a strong 136 \ninduction of mul-1 across all gut cells at every developmental stage, most notably in the anterior 137 \ntwo nuclei (Fig.  1B, C-D, red lines) . The induction is dose- and time-dependent, becoming 138 \ndetectable after 2 hours and peaking at 6 hours (Figs. S1, S2) . For Western blotting, we 139 \ngenerated a knock-in strain with a C-terminal 3xHA tag at the endogenous mul-1 locus. In 140 \nuntreated controls, MUL-1::3xHA protein was undetectable by immunoblotting, consistent with 141 \nvery low basal expression (Fig. 1). However, 6 hours after IR treatment, a specific ~35 kDa 142 \nband corresponding to the predicted molecular weight appears (Fig. S3). 143 \n 144 \nTo determine if the induction of mul-1 is specific to IR-induced DNA damage, we tested other 145 \ngenotoxic agents. Neither cisplatin, a DNA crosslinking agent, nor methyl methanesulfonate 146 \n(MMS), an alkylating agent, induced mul-1 expression (Fig. 2A-D, F) . In contrast, some 147 \ninduction was observed following UV treatment (Fig. 2E, F) . UV exposure not only generates 148 \ncyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4 PPs) but also produces ROS 149 \nthrough photochemical reactions (Yoshiyama et al., 2023), suggesting that mul-1 induction 150 \nmight be linked to oxidative stress rather than DNA damage itself. Additionally, no induction was 151 \nobserved after starvation, heat shock, or osmotic stress (Fig. 3A-D, K). However, a strong 152 \ninduction occurred after exposure to H 2O2, a potent ROS generator that produces hydroxyl 153 \nradicals (∙OH) and superoxide anions (O2-) (Kumsta et al., 2011) (Fig. 3E, K). ROS are also 154 \nproduced during normal metabolism, and the two 2-Cys peroxiredoxins, PRDX-2 and PRDX-3, 155 \nserve as key antioxidants, with PRDX-2 playing a vital role in detoxifying H 2O2. Loss of PRDX-2 156 \nresults in increased sensitivity to H 2O2, a shortened lifespan, and developmental abnormalities 157 \n(Kumsta et al., 2011; Oláhová et al., 2008). To investigate whether impaired H 2O2 detoxification 158 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n8 \n \ncan trigger mul-1 induction, we used CRISPR/Cas9 to introduce the prdx-2(gk169)  mutation into 159 \nmul-1(syb3342) animals. Under normal conditions, basal mul-1 expression in prdx-2(gk169);  160 \nmul-1(syb3342) animals was similar to that of controls during early larval stages (Fig. 3F). 161 \nHowever, as development progressed, mul-1 transcription first appeared in anterior gut cells. It 162 \ngradually expanded along the intestine, eventually resulting in widespread, strong expression in 163 \nadult animals (Fig. 3G-J, L). Our results suggest that both exogenous and endogenous ROS 164 \ninduce mul-1 expression.  165 \n 166 \nThe p38 MAPK pathway and its downstream effector ATF-7 regulate mul-1  167 \nNext, we examined the role of key stress response pathways in regulating mul-1. Previous RNAi 168 \nstudies and quantitative PCR showed that both the p38/PMK-1 and insulin/IGF-1 signaling 169 \npathways are necessary for mul-1 induction after IR treatment (Kimura et al., 2012). Using our 170 \nmul-1 transcriptional reporter, we systematically dissected the contribution of the p38/PMK-1 171 \npathway and its downstream effectors, including SKN-1 and ATF-7, as well as the upstream 172 \nregulator SEK-1, in response to IR-induced DNA damage. In C. elegans, the TIR-1-NSY-1-SEK-173 \n1-PMK-1 signaling cascade mediates the innate immune response in the gut (Inoue et al., 174 \n2005). SEK-1 (stress-activated protein kinase-1 ), a mitogen-activated protein ki nase kinase 175 \n(MAPKK), acts upstream of p38/PMK-1, modulating its activity  through phosphorylation in 176 \nresponse to various stress stimuli, including infection, oxidative stress, or environmental insults 177 \n(Kim et al., 2002). We found that IR-induced mul-1 upregulation is compromised in sek-1(km4) 178 \nand pmk-1 (km25) mutants (Fig. 4A-C, F) . We also found that ATF-7, but not the SKN-1 179 \ndownstream effector, is required for mul-1 induction (Fig. 4D-F). ATF-7 and SKN-1 have distinct 180 \nroles downstream of p38/PMK-1. SKN-1 mediates responses to oxidative stress by regulating 181 \nclassical phase II detoxification genes, whereas ATF-7 governs immune responses, such as 182 \nresistance to P. aeruginosa (Foster et al., 2020; Zhu et al., 2022). Although mul-1 induction was 183 \nstrongly reduced in atf-7 mutants, a residual response remained detectable, suggesting that 184 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n9 \n \nadditional factors may contribute to mul-1 activation in parallel with ATF-7 (Fig. 4E-F). Mutations 185 \nin the daf-2 insulin receptor and the daf-16 transcription factor show no effect on mul-1 induction 186 \n(Fig. S4). 187 \n 188 \nTo visualize MUL-1 protein, we created a translational reporter, mul-1::linker::eGFP(gt3545). 189 \nDetecting MUL-1 was challenging due to autofluorescence from gut granules, which interfered 190 \nwith signal clarity. To overcome this, we introduced the glo-1(zu391) mutation, which disrupts 191 \ngut granule formation, thus reducing autofluorescence without affecting intestinal function 192 \n(Hermann et al., 2005) (Fig. 5A). Under control conditions, MUL-1 expression was not 193 \ndetectable in the mul-1(gt3545); glo-1(zu391) reporter strain (Fig. 5B, F, G-H) . After IR and 194 \nH2O2 treatment, MUL-1 expression was induced, resulting in a low but visible diffuse 195 \ncytoplasmic signal in intestinal cells, along with distinct cytoplasmic puncta (Fig. 5C, D, F), MUL-196 \n1 expression was increased in prdx-2(gk169);  mul-1(gt3545); glo-1(zu391) animals, indicating 197 \nthat endogenous oxidative stress promotes MUL-1 induction (Fig. 5I-J) in line with the 198 \ntranscriptional induction (Fig. 3I, J, L) . An intense cytoplasmic signal can be observed in a high 199 \ncopy MUL-1::eGFP transgene (Fig. 5E) (Hoffman et al., 2020).  200 \n 201 \nMUL-1 mitigates oxidative stress and modulates DNA damage-induced germ cell 202 \napoptosis 203 \nWe could not identify an overt phenotype associated with the mul-1 reporter line lacking the 204 \nopen reading frame under basal conditions, based on progeny numbers,  embryonic lethality, or 205 \nlifespan (Fig. 6A-C). Additionally, after exposure to IR, we did not observe any deviation from 206 \nwild type in developmental progression from the L1 stage or in progeny survival at the L4 stage 207 \n(see below, Fig. 7G). To further explore the role of mul-1 in oxidative stress management, we 208 \nused the CellROX Green assay. This fluorescent probe detects multiple ROS, including H 2O2, 209 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n10 \n \nsuperoxide, and hydroxyl radicals (Palacin-Martinez et al., 2024). Under control conditions, both 210 \nwild-type and mul-1(syb3342) mutants showed minimal green fluorescence, indicating low basal  211 \nROS levels (Fig. 6D, E, G) . Following IR exposure, wild-type animals showed a moderate 212 \nincrease in ROS levels (Fig. 6D, F) , whereas mul-1(syb3342)  mutants exhibited a stronger 213 \nsignal, especially in intestinal cells (Fig. 6D, H) . We then directly tested sensitivity to H 2O2 214 \nexposure and first identified the most suitable concentration, finding that L1 worms treated with 215 \n1 mM H2O2 developed normally, while those treated with 5 mM H 2O2 were uniformly arrested at 216 \nthe L1 stage; treatment with 2.5 mM resulted in an intermediate response (Fig. S5A) . When 217 \nassessing sensitivity to 2.5 mM H 2O2, we observed that developmental progression was 218 \nmoderately delayed in mul-1(syb3342), comparable to daf-16 and pmk-1 mutants, which served 219 \nas positive controls (Fig. 6I). 220 \n 221 \nNext, we analyzed germ cell apoptosis using a widely used reporter where the CED-1 apoptotic 222 \ncorpse receptor is tagged with GFP (Zhou et al., 2001). Under basal conditions, mul-1(syb3342) 223 \nanimals exhibited normal levels of apoptosis  (Fig. 6J, lanes 1 and 5) . In contrast, following IR, 224 \napoptosis was hyperinduced in mul-1(syb3342), a finding confirmed when using a second mul-1 225 \nallele (Fig. 6J, lanes 2, 6, 8). Excessive IR-dependent apoptosis was suppressed in cep-226 \n1(lg12501), which is defective for the nematode p53-like transcription factor (Fig.  6J, lanes 4 227 \nand 10). Complementation analyses using mul-1::eGFP and mul-1::3xHA alleles under the 228 \nsame conditions confirmed that both tagged MUL-1 proteins are functional, as they  suppress 229 \nthe extra apoptosis phenotype of mul-1 to wild-type apoptosis levels (Fig. S5B). 230 \n 231 \nMUL-1 belongs to a conserved ShKT-containing gene cluster that modulates oxidative 232 \nstress and germline homeostasis 233 \n 234 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n11 \n \nWe aimed to investigate if mul-1 might act redundantly. Performing BLAST searches for MUL-1 235 \nparalogs and scanning through the WormBase we indeed found multiple MUL-1 paralogs. mul-1 236 \nis part of a four-gene cluster on chromosome IV that includes three additional closely related 237 \ngenes (drd-50, F49F1.5, F49F1.7) (Fig. 7A, B, Suppl. Table 1). MUL-1 paralogs contain multiple 238 \nShKT domains with six conserved cysteines, forming three disulfide bonds that stabilize a 239 \ncompact double α -helix structure (Fig. 7A). This clustering suggests potential co-regulation or 240 \nshared functions. Consistent with this, transcriptional analysis revealed a strong induction of 241 \nmul-1 upon IR, whereas its paralogs display only modest changes, indicating differential 242 \nregulation within the cluster  (Fig. S6A). We refer to the syb8776 mutation when taking out all 4 243 \nparalogs as the ‘quadruple mutant’ (Fig.7C). To test for redundancy, we started by analyzing the 244 \nquadruple mutant and focused on developmental progression and  lifespan, a key measure of 245 \norganismal resilience affected by genes involved in stress response, genomic stability, and 246 \ncellular homeostasis. 247 \n 248 \nWhile wild-type or single deletions of mul-1 or pmk-1  do not impair developmental progression 249 \nfollowing IR, the quadruple mutant exhibits delayed larval development, indicating functional 250 \nredundancy among MUL-1 paralogs during recovery from genotoxic stress.maintenance 251 \n(López-Otín et al., 2023). The quadruple  mutant showed no change in lifespan compared to 252 \nwild-type (Fig. 7D). However, the quadruple mutant had a significant reduction in progeny (Fig. 253 \n7 254 \nE). In contrast, no embryonic lethality was observed in the quadruple mutant, similar to the wild-255 \ntype (Fig. 7F). Importantly, expression of the multicopy mul-1(gtIs3000) transgene restored 256 \nbrood size in the quadruple mutant without affecting embryonic survival ( Fig. S6B-C). We then 257 \ntested if reduced progeny in the quadruple mutant was correlated with excessive germ cell 258 \napoptosis and found that it was the case, both with and without IR treatment (Fig. 7G). 259 \nExcessive apoptosis was CEP-1/p53 dependent under both conditions. Given the redundancy 260 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n12 \n \nof MUL-1-like proteins, we tested whether larval development is delayed upon treating L1 stage 261 \nanimals with IR, and found that this is true for the quadruple mutant (Fig. 7H). In contrast, single 262 \ndeletions of mul-1 or pmk-1 do not impair developmental recovery after IR, the combined loss of 263 \nmul-1 paralogs slows development. 264 \n 265 \nMUL-1 paralogs protect from Pseudomonas aeruginosa infection 266 \nWe hypothesized that MUL-1 and its closely related paralogs may protect against bacterial 267 \ninfection, commonly associated with oxidative stress.  Therefore, we tested susceptibility to P. 268 \naeruginosa PA14 infection, a model commonly used in vertebrates and C.  elegans (Tan et al., 269 \n1999), and known to induce oxidative stress in the nematode (Zhang et al., 2025). We observed 270 \nthat mul-1(syb3242) animals died slightly earlier than wild type, with the quadruple mutant being 271 \nthe most sensitive, comparable to the pmk-1 positive control (Fig. 8A).  mul-1 expression was 272 \nrobustly induced upon exposure to PA14, as indicated by increased reporter fluorescence 273 \nintensity relative to OP50-fed controls (Fig. 8B-D).  274 \n 275 \nLoss of MUL-1 paralogs activates oxidative stress response pathways via daf-16/FoxO 276 \nand skn-1/Nrf2 277 \nIf MUL-1-like proteins act by scavenging or sensing oxidative stress, their absence might lead to 278 \nincreased endogenous ROS and possibly activate compensatory stress-response pathways. 279 \nWe thus tested if ROS is induced in the quadruple mutants even in the absence of IR, and 280 \nfound that this is the case using the CellROX green assay (Fig. 9A-C).  281 \n 282 \nTo examine if this leads to the activation of compensatory pathways, we investigated oxidative 283 \nstress response pathways regulated by daf-16/FoxO and skn-1/Nrf2 (Doonan et al., 2008; Inoue 284 \net al., 2005; Leiers et al., 2003). We generated translational reporters for sod-3 and gst-4 to 285 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n13 \n \nassess pathway activation by fusing eGFP to sod-3 (sod-3(gt3598)) and mCherry to gst-4 (gst-286 \n4(gt3596)). We combined both reporters with the glo-1(zu391)  mutation to reduce 287 \nautofluorescence from intestinal gut granules (Hermann et al., 2005). sod-3 encodes a 288 \nmitochondrial manganese superoxide dismutase (MnSOD), which neutralizes superoxide 289 \nradicals and is often linked to increased stress resistance and longevity (Doonan et al., 2008). 290 \nGST-4 is a phase II detoxification enzyme, glutathione S-transferase, which has a peroxidase 291 \nactivity and catalyzes the c onjugation of glutathione (GSH) to electrophilic compounds, 292 \npromoting detoxification and excretion (Hurst et al., 1998; Inoue et al., 2005; Leiers et al., 2003). 293 \nAnalysis of GST-4::mCherry and SOD-3::eGFP expression in wild-type L1 larvae confirmed that 294 \nGST-4 is primarily expressed in the intestine, with additional localization in head hypodermal 295 \ncells (Fig. 10A). In contrast, SOD-3::eGFP fluorescence was localized to the pharynx, especially 296 \nin the anterior bulb, with a faint but detectable signal around the terminal bulb of the pharynx. 297 \nNo sod-3 expression was observed in the intestine under normal conditions, nor in the 298 \nhypodermis, body wall muscles, neurons, or tail (Fig. 10A) . Deletion of mul-1 alone did not 299 \nsignificantly change GST-4 expression but increased SOD-3 expression in the pharynx (Fig. 300 \n10B). Remarkably, the F49F1(syb8776)  quadruple deletion caused a strong induction of GST-4 301 \nthroughout the body, especially in the anterior gut, with widespread upregulation of SOD-3 (Fig. 302 \n10C). Consistent with these findings, prdx-2 mutants, which are known to accumulate 303 \nendogenous ROS and which we show to induce mul-1 (Fig. 3 and 5), also showed strong GST-304 \n4 induction and pharyngeal SOD-3 expression (Fig. 10D) . As expected, GST-4 induction in 305 \nprdx-2 mutants was skn-1 -dependent (Fig. 10E) , while SOD-3 induction required daf-16 (Fig. 306 \n10F). Overall, these results suggest that deleting mul-1 and its paralogs increases oxidative 307 \nstress and the expression of key genes involved in oxidative stress response.  308 \n 309 \nGenetic interaction with further MUL-1 paralogs 310 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n14 \n \nOur results are consistent with MUL-1 proteins acting redundantly to protect animals from 311 \noxidative stress. Given that the nematode genome encodes multiple additional MUL-1 paralogs 312 \nwe wanted to test this notion more generally and examined a more distantly related MUL-1 313 \nparalog SYSM-1, given its reported role as an apoptosis effector, deficiency leading to 314 \ndecreased, and not increased DNA damage induced germ cell apoptosis. SYSM-1 acts cell-non 315 \nautonomously, being secreted from the gut and functioning independently of p53 316 \n(Soltanmohammadi et al., 2022). We confirmed that sysm-1 mutants are defective for DNA 317 \ndamage-induced apoptosis (Soltanmohammadi et al., 2022) (Fig. 11A) . However, analysis of 318 \nsysm-1; mul-1 double mutants as well as quadruple mutant in conjunction with sysm-1 revealed 319 \nthat the excessive apoptosis phenotype observed in mul-1 single mutants as well as in the 320 \nquadruple mutant where excessive apoptosis occurs even without IR is not suppressed by  321 \nsysm-1. In other words, the apoptosis defect associated with sysm-1 is bypassed by  mul-1 and 322 \nits paralogs (Fig. 11A). 323 \n 324 \nWe next generated and analysed syb8669 a deletion of F46B3.1, the most closely related MUL-325 \n1 paralog located outside the MUL-1 paralog cluster (quadruple mutant). Double mutant 326 \nanalysis of the allele leads to complex genetic interactions with mul-1 and the quadruple mutant: 327 \nWhile the single mutant has no overt phenotype compared to N2, the quintuple mutant 328 \nsuppressed some phenotypes, while enhancing others. syb8669 suppressed the reduced 329 \nfecundity of the quadruple mutant (Fig.11B). Conversely, the reduced H 2O2 sensitivity of the 330 \nquadruple mutant was further suppressed to an extent such that quintuple mutants are partially 331 \nresistant compared to WT (Fig. 11C). Also, the hypersensitivity towards Pseudomonas PA14 of 332 \nthe quadruple mutant is suppressed in the quintuple mutant (Fig. 11D). In contrast, quintuple 333 \nmutants are hypersensitive to IR (Fig. 11E). All in all, the experiments including sysms-1 and 334 \nsyb8669 point towards a more complex picture where MUL-1 paralogs can have opposing 335 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n15 \n \nfunctions, in line with the hypothesis that MUL-1 like proteins might besides being scavengers 336 \nmay also act as rheostates for ROS. 337 \n 338 \nDiscussion 339 \nWe initiated our study by focusing on MUL-1 and later included the four closest paralogs in our 340 \nanalyses. MUL-1 and its close paralogs are unstructured, except for possessing 3-5 ShKT 341 \ndomains. These domains are cysteine-rich motifs initially described in sea anemone toxins and 342 \nare widely found in invertebrate proteins, although their function in nematodes remains largely 343 \nunexplored (Rangaraju et al., 2010; Sachkova et al., 2020). We postulate that nematode multi-344 \nShKT domain proteins may act as scavengers or rheostats of oxidative stress, owing to their 345 \npotential to scavenge ROS via disulfide formation facilitated by the six cysteines in each ShKT 346 \ndomain (Fig. 12, see below). 347 \n 348 \nWe certainly do not rule out that MUL-1 and its paralogs are mucin-like proteins (Hoffman et al., 349 \n2020). MUL-1 encodes a 42-amino-acid domain highly enriched in serine/threonine residues, 350 \nwhich is akin to mammalian mucins that are highly enriched for serine/threonine throughout 351 \nmost of their length. The parasitic nematode Toxocara canis encodes four secreted proteins, 352 \neach with an N-terminal signal peptide for secretion and an 83-97 amino acid S/T-enriched 353 \nmucin domain, N-terminal to two ShkT domains (Loukas et al., 2000). For MUL-1, prominent 354 \nenrichment of serine and threonine residues, which occurs along the entire length of 355 \nmammalian mucins comprising several thousand amino acids (Johansson et al., 2013), occurs 356 \nonly in a 44-amino-acid unstructured region between the 4th and 5th ShKT domains. 357 \nIrrespective, our combined genetic analysis indicates that MUL-1 and related paralogs are 358 \ninvolved in a circulatory regulatory circuit associated with oxidative stress as discussed below.  359 \n 360 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n16 \n \nWe discovered that the transcriptional induction of MUL-1 by IR, which generates ROS, is 361 \nrestricted to the gut, with the most pronounced effects observed in the anterior cells. Notably, 362 \nMUL-1 induction is not triggered by DNA-damaging agents such as the methylating agent MMS 363 \nor the DNA cross-linking agent cisplatin, nor by osmotic stress or starvation, but rather by 364 \noxidative stress, as demonstrated by direct exposure to H 2O2 or increased endogenous H 2O2 365 \nlevels in peroxidase-deficient prdx-2 mutants . mul-1  induction is medi ated by the p38 MAPK 366 \nsignaling pathway, consistent with previous RNAi-based studies (Kimura et al., 2012), and 367 \nrequires the transcription factor ATF-7, but not SKN-1. While SKN-1 is widely recognized as a 368 \nmaster regulator of oxidative stress responses by inducing phase II detoxification genes 369 \n(Blackwell et al., 2015; Foster et al., 2020), our findings underscore a previously 370 \nunderappreciated role for ATF-7 in orchestrating transcriptional responses to ROS 371 \naccumulation. At first glance, gut expression seems intriguing; however, it aligns with bacterial-372 \nnematode infections, in which bacterial pathogens and C. elegans produce ROS upon pathogen 373 \nexposure (Chavez et al., 2007; Hoeven et al., 2011; Jansen et al., 2002; Miranda-Vizuete & 374 \nVeal, 2017) . Indeed, Rhizobium infection and the associated oxidative stress led to defective 375 \ngenome integrity during larval gut development, resulting in excessive DNA bridges and 376 \nkaryokinesis defects in gut nuclei, with the phenotype most prominent in the anteriormost gut 377 \ncells (Kniazeva & Ruvkun, 2019). We di d not find decreased susceptibility to P. aeruginosa 378 \ninfection in the  mul-1 single mutant, as previously reported (Hoffman et al., 2020), but did find 379 \nincreased sensitivity in the quadruple mutant. This is due to us using 5-fluoro-2’-deoxyuridine 380 \n(FUDR) to prevent germ cell proliferation, animals otherwise producing embryos that hatch 381 \ninside their parents (bagging phenotype) leading to lethality (Kwon et al., 2024). 382 \n 383 \nFunctionally, in our study, mul-1 mutants exhibited a small increase of ROS after IR, a modest 384 \ndelayed development under oxidative stress conditions, and elevated CEP-1-dependent germ 385 \ncell apoptosis. mul-1 is part of a cluster of three additional paralogs, each encoding three to five 386 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n17 \n \nShKT domains. Deleting these three paralogs, along with mul-1 (quadruple mutant), reduced 387 \nprogeny numbers and exhibited CEP-1/p53-dependent germline apoptosis even without 388 \nirradiation. Also, genetic interactions with SYSM-1, a small, 99-amino-acid, unstructured protein 389 \nthat carries two ShKT domains and is induced by IR (Soltanmohammadi et al., 2022), yielded 390 \nsurprising results. Like MUL-1, SYSM-1 is a transcriptional target of p38 signaling and the 391 \ndownstream ATF-7 transcription factor (Soltanmohammadi et al., 2022). In contrast to MUL-1, 392 \nwhich reduces CEP-1 p53-induced germ cell apoptosis, SYSM-1 is essential for DNA damage-393 \ninduced apoptosis. We find that radiation-induced apoptosis of sysm-1 mutants is bypassed by 394 \nmul-1 single and quadruple mutants. SYSM-1 was suggested to be secreted from the gut to 395 \nfacilitate DNA damage-induced apoptosis in the germ line (Soltanmohammadi et al., 2022). 396 \n 397 \nWe show that in the absence the 4 MUL-1 paralogs, endogenous ROS accumulates, and this 398 \naligns with our observation that DAF-16-dependent SOD-3::eGFP and SKN-1-dependent 399 \nCherry::GST-4 are induced in the mul-1 quadruple paralog mutant. Together, these data 400 \nsupport a circular model of redox signaling, in which MUL-1 and MUL-1-like ShKT domain 401 \nproteins may function as scavengers or rheostats of ROS (Fig. 12). This way, the loss of the 402 \nMUL-1 cluster may lead to increased oxidative stress and the compensatory activation of stress 403 \npathways, conferring increased survival under oxidizing conditions, but is insufficient to protect 404 \nagainst apoptosis induction, sensitivity to IR and Pseudomonas infection. A localized balance 405 \nbetween the expression of various MUL-1 paralogs and the differential activation of 406 \ncompensatory pathways might determine the activity of different stress response pathways. At 407 \npresent, we do not know how signals associated with mul-1 single and compound mutants are 408 \ntransmitted across worm tissues, especially to the germ line, where CEP-1-dependent apoptosis 409 \nis induced. Signaling, and this hypothesis remains to be tested, might be conferred via direct 410 \ntranslocation of closely related MUL-1 paralogs, as shown for SYSM-1 (Soltanmohammadi et 411 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n18 \n \nal., 2022). Alternatively, intercellular signalling could be directly mediated by H 2O2 diffusion 412 \nacross plasma membranes mediated by aquaporins (Sies & Jones, 2020).  413 \n 414 \nShKT domains were initially characterized as potent toxins derived from sea anemones that 415 \ninhibit mammalian potassium channels (Castañeda et al., 1995; Harvey & Vita, n.d.; Shafee et 416 \nal., 2019; Tudor et al., 1998). We postulate that ShKT domains may be involved in redox 417 \nreactions. If so, ShKT domains are used in redox regulation, and their cysteines could be 418 \noxidised akin to the 3 amino acid GSH (glutathione) peptide to its oxidized dimeric (GSSG) 419 \nform. Each ShKT domain contains six cysteine residues, potentially allowing for extensive 420 \ndisulfide bond formation and redox reactivity. Although such a system may appear inefficient, 421 \nespecially if reductive recycling does not occur, it could serve as a buffering mechanism during 422 \nacute oxidative stress. In this context, the expansion of proteins primarily composed of ShKT 423 \ndomains in nematodes and other invertebrates might reflect an evolutionary strategy to cope 424 \nwith transient yet potentially lethal oxidative insults. Akin, peroxiredoxin ShKT domains might act 425 \nas direct H 2O2 scavengers or enable thiol oxidation by relaying H 2O2-derived oxidation 426 \nequivalents to other proteins (Stöcker et al., 2018). 427 \n 428 \nThe hypothesis that ShKT domains might be linked to redox reactions is supported by 429 \ninvertebrate redox-active proteins, such as peroxidases and tyrosinases that carry ShKT 430 \ndomains (Rangaraju et al., 2010). For instance, C. elegans  MLT-7 and SKPO-1, 2, and 3, 431 \nperoxidases have acquired an N-terminal ShKT domain and are closely related to the human 432 \nperoxidasin PXDN which lacks a ShKT domain (Thein et al., 2009; Tiller & Garsin, 2014). These 433 \nproteins have been shown to crosslink collagen and regulate endothelial basement membrane 434 \nstructure and protect against E. faecalis  infection (Thein et al., 2009; Tiller & Garsin, 2014). 435 \nPeroxidase reactions use H 2O2 to catalyze the oxidation of various substrates, and C. 436 \nelegans peroxidases modify cuticle collagen structure and permeability (Edens et al., 2001; 437 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n19 \n \nMyllyharju & Kivirikko, 2004; Thein et al., 2009). Beyond peroxidases, ShKT domains are also 438 \npresent in several C. elegans  tyrosinases-like proteins (TYR-1 through TYR-6), which belong to 439 \nthe type-3 copper enzyme family and are annotated to contain tyrosinases copper-binding 440 \ndomains together with an N-terminal ShKT module. Although the specific biochemical activities 441 \nof TYR proteins in C. elegans  remain untested and are inferred primarily from homology, 442 \nmammalian tyrosinases are well-established type-3 copper oxidoreductases that function 443 \nthrough catalytic redox cycling (Pretzler & Rompel, 2024).  444 \n 445 \nOverall, our combined results indicate that MUL-1-like proteins may act as buffers or rheostats 446 \nfor oxidative stress. It remains to be directly tested if and when ShKT domains are oxidised and 447 \nif this involves disulfide bond formation. Certainly, it is possible, and this remains to be tested, 448 \nthat MUL-1 like proteins have a role in connecting neuronal circuits and gut behavior, where 449 \nH2O2 has a role in signaling (Jia et al., 2024; Jia & Sieburth, 2021; Liu et al., 2024). Irrespective, 450 \nthe expansion of ShKT domains  in nematodes and other invertebrates may facilitate rapid 451 \nevolutionary adaptation to the various challenges posed by oxidative stress. The expansion of 452 \nMUL-1 paralogs may also have facilitated different MUL-1 paralogs having overlapping and 453 \nopposing functions.  454 \n 455 \nLimitations of the study.  456 \nOverall, our combined results indicate that MUL-1 is part of a regulon induced by oxidative 457 \nstress via p38 MAP kinase signaling, and that MUL-1 and its paralogs may act as buffers or 458 \nrheostats for oxidative stress. It remains to be directly tested if and when ShKT domains are 459 \noxidised and if this involves disulfide bond formation. MUL-1 paralog SYSM-1 was previously 460 \nshown to be secreted from the gut and taken up in the germ line. Analysing high copy MUL-1 461 \nwe do not see any evidence for germ line localization, but acknowledge that this might be due to 462 \nthe limited sensitivity of GFP.  We recognize that we have not investigated if MUL-1 and its 463 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n20 \n \nparalogs act cell non-autonomously,  which will be an interesting future question. Also, our 464 \nanalysis largely depends on the analysis of the mul-1 single mutant and the quadruple mutant 465 \nwhere all 4 paralogs of the locus are deleted. It will be interesting to investigate how all single, 466 \ndouble and triple mutant combinations behave relating to apoptosis induction, H 2O2 resistance, 467 \nthe accumulation of ROS as well as the activation of compensatory GST-4 and SOD-3 468 \nactivation. Finally,  we acknowledge that we do not provide direct evidence that the heightened 469 \nsensitivity of the quadruple mutant to Pseudomonas infection  PA14 is due to excessive 470 \noxidative stress.  471 \n 472 \nMaterials and Methods  473 \n 474 \nExperimental design 475 \nThe aim of this study was to determine if and how MUL-1 and its ShKT-domain paralogs 476 \nregulate organismal responses to oxidative stress and DNA damage in C. elegans . We used 477 \ngenetically defined wild-type and mutant strains to compare responses to IR, chemical 478 \ngenotoxins, oxidative stress, osmotic stress, heat shock, starvation, and Pseudomonas 479 \naeruginosa infection. Stress-induced signaling and ROS levels were monitored using single 480 \ncopy fluorescent transcriptional and translational reporters at endogenous loci, CellROX 481 \nstaining, and quantitative microscopy. Strains were generated by CRISPR-Cas9 genome editing 482 \nand genetic crosses. Alleles were validated by PCR and sequencing. All assays were performed 483 \nwith age-synchronized populations. Phenotypic outcomes were quantified using standardized 484 \nassays. All experiments included at least three independent biological replicates. Sample sizes 485 \nvaried depending on the assay and are indicated in the corresponding figure legends. For most 486 \nmicroscopy-based assays, 20-30 animals per condition were analyzed, whereas lifespan and 487 \nprogeny assays were performed using assay-appropriate cohort sizes. The number of animals 488 \n(n) refers to individual worms scored per condition, unless otherwise specified. 489 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n21 \n \n 490 \nStrain maintenance and genetics 491 \nCaenorhabditis elegans  strains were maintained using standard procedures as originally 492 \ndescribed by Brenner (Brenner, 1974). Animals were cultured on NGM-lite agar plates seeded 493 \nwith Escherichia coli OP50 and maintained at 20°C under standard laboratory conditions unless 494 \notherwise indicated. For specific assays, animals were propagated at 25°C (e.g., P. aeruginosa 495 \nPA14 survival assays) or at 15°C for the maintenance of selected strains. Strains are listed 496 \nunder Suppl Table 2. 497 \n 498 \nAge-synchronized populations were generated either by alkaline hypochlorite treatment of 499 \ngravid adults followed by overnight L1 arrest in M9 buffer, or by filtration-based synchronization 500 \nmethods, as indicated. Transgenic and CRISPR-Cas9-edited strains were generated by 501 \nstandard microinjection protocols (Dokshin et al., 2018; Ghanta & Mello, 2020; Wang et al., 502 \n2018) or obtained from the Caenorhabditis Genetics Center (CGC) or SunyBiotech. Compound 503 \nmutant strains were generated through standard genetic crosses and verified by PCR 504 \ngenotyping and/or DNA sequencing. All strains used in this study are listed in Suppl. Table 2, 505 \nand corresponding reagents can be found in Suppl. Table 3. 506 \n  507 \nGenotoxic stress analysis 508 \nFor IR experiments, age-synchronized animals were exposed to X-rays using an RS2000 X-ray 509 \nirradiator (Rad Source Technologies) operated at 160 kV and 25 mA with a 0.3 mm copper filter, 510 \nas previously described (Ermolaeva et al., 2013; Zou et al., 2024). Following irradiation, animals 511 \nwere returned to OP50-seeded NGM plates and allowed to recover under standard conditions. 512 \n 513 \nFor chemical genotoxic stress assays, freshly prepared aliquots of cisplatin dissolved in saline 514 \nand MMS diluted in water were used according to established protocols (Volkova et al., 2020). 515 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n22 \n \nAll solutions were protected from light until use. Groups of 20-30 age-synchronized animals 516 \nwere transferred into 2 mL of S-basal buffer supplemented with 5 μ l of concentrated OP50 517 \nbacterial suspension as a food source. For MMS treatment, animals were exposed to 0.8 mM 518 \nMMS for 16 h at 20 °C, as previously reported. For cisplatin treatment, animals were incubated 519 \nwith 10 μ M cisplatin for 16 h at 20 °C. Samples were incubated under gentle agitation 520 \nthroughout the treatment period. After exposure, animals were washed thoroughly to remove 521 \nresidual genotoxins, transferred to OP50-seeded NGM plates, and allowed to recover. 522 \n 523 \nFor UV irradiation, age-synchronized animals were placed on unseeded NGM plates without lids 524 \nand exposed to 200 mJ/cm 2 UV light using a CL-1000 UV crosslinker (UVP), as previously 525 \ndescribed (Yue et al., 2024). Animals were transferred immediately to OP50-seeded NGM 526 \nplates following exposure and imaged 24 h post-treatment. 527 \n 528 \nWestern blot analysis of MUL-1::3xHA 529 \nSynchronized C. elegans  populations were collected and washed three times with M9 buffer, 530 \nflash-frozen in liquid nitrogen and stored at -80°C. Worm pellets were thawed on ice and mixed 531 \n1:1 with a 2x Laemmli buffer containing 5% β -mercaptoethanol, boiled at 95°C for 5 min, and 532 \nbriefly centrifuged. Proteins were resolved on hand-cast 12% SDS-PAGE gels in Tris-glycine-533 \nSDS buffer (Jeong et al., 2018) and transferred to a PVDF membrane using a semi-dry system 534 \n(15V, ~0.8 mA cm -2, 15 min). Membranes were blocked in 5% non-fat milk in PBST for 1h, 535 \nincubated with mouse anti-HA (sigma, clone 16B12; 1:1000) overnight at 4°C, washed and 536 \nprobed with HRP-conjugated anti-mouse secondary antibody (1:5000) for 1h. Signals were 537 \ndetected using Pierce ECL Plus substrate and imaged on a Bio-Rad Chemidoc system. 538 \n  539 \nMicroscopy and image acquisition 540 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n23 \n \nImages were acquired on a Zeiss Axio Imager microscope equipped with an Axiocam 503 mono 541 \ncamera and controlled by ZEN softwar e. Z-stacks were  collected at 1 μ m intervals. For each 542 \nexperiment, exposure times, illumination intensity, and acquisition settings were kept constant 543 \nacross all genotypes and conditions. Detailed acquisition parameters for each experiment are 544 \nprovided in the corresponding Methods section.  545 \n 546 \nQuantification of intestinal nuclei fluorescence 547 \nFluorescence intensity from the transcriptional reporter, and from all mutant strains generated in 548 \nthis reporter background, was quantified by performing line-scan measurements across the first 549 \npair of anterior intestinal nuclei in mul-1(syb3342) IV animals. A transverse (10 pixels wide) line 550 \nwas manually positioned through the nuclei, spanning 30 μ m in L1-L3 larvae or 40 μ m in L4 and 551 \nadult animals. Line placement was optimized to minimize background contributions from 552 \nadjacent intestinal cells and out-of-focus planes. For each nucleus, the maximum fluorescence 553 \nintensity peak along the line profile was extracted and used for quantitative analysis. 554 \n 555 \nFor translational reporters and CellROX green staining, fluorescence intensity was quantified by 556 \nmeasuring the corrected total cell fluorescence (CTCF). Images were acquired as z-stacks, and 557 \na single optical section representing a comparable focal plane was selected for each animal. 558 \nWhole-animal regions of interest (ROIs) were manually delineated for individual animals, and 559 \nCTCF values were calculated as the integrated fluorescence intensity after background 560 \nsubtraction and used for quantitative analysis. 561 \n 562 \nStress response experiments 563 \nTo assess stress responses, age-synchronized C. elegans  at the indicated developmental 564 \nstages were subjected to defined stress conditions, following established protocols. 565 \n 566 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n24 \n \nFor starvation stress, L1 larvae were transferred to unseeded NGM plates and incubated at 20 567 \n°C for 6 h, as previously described for starvation-induced stress responses ( P MC369 79 62 ). For 568 \nosmotic stress, synchronized L1 animals were placed on OP50-seeded NGM plates 569 \nsupplemented with 250 mM NaCl and incubated for 24 h at 20 °C, following standard 570 \nhyperosmotic stress assays (Urso et al., 2020). For heat-shock treatment, synchronized L4 571 \nanimals were incubated on OP50-seeded NGM plates at 35 °C for 1 h, followed by a 1 h 572 \nrecovery period at 20 °C, as previously described (Golden et al., 2020; Lithgow et al., 1995). For 573 \noxidative stress, synchronized L1 animals were exposed to 10 mM H2O2 in liquid culture. Briefly, 574 \nanimals suspended in M9 buffer were treated by adding 10 μ l of a 5x H 2O2 stock solution to 40 575 \nμ l of the animal suspension and incubated for 1 h at 20 °C under gentle agitation (Offenburger & 576 \nGartner, 2018). After treatment, animals were washed four times with 1 mL M9 buffer to remove 577 \nresidual H2O2 transferred to OP50-seeded NGM plates, and incubated at 20 °C. Animals were 578 \nimaged 24 h post-treatment. 579 \n  580 \nGeneration of a stable integrated multicopy mul-1::eGFP line 581 \nA multicopy mul-1::eGFP reporter line was generated by first establishing an extrachromosomal 582 \narray in the temperature-sensitive lin-15(n765) background using a PCR-amplified mul-583 \n1P::linker::eGFP fragment co-injected with the rescue plasmid pL15EK. Transgenic F1 animals 584 \nshowing robust intestinal GFP expression and phenotypic rescue of the lin-15  defect were 585 \nselected. To obtain a stable genomic insertion, animals carrying the array were exposed to 50 586 \nGy of IR, and subsequent generations were screened for lines that maintained uniform GFP 587 \nexpression in the absence of selection, indicative of successful array integration. 588 \n 589 \nAnalysis of mitochondrial ROS 590 \nA 5x CellROX green solution was prepared by diluting the 2.5 mM stock solution in M9 buffer 591 \nand protected from light until use, as previously described for ROS detection in C. elegans (Min 592 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n25 \n \net al., 2021) For each reaction, synchronized L1 animals were collected in M9, and 160 μ l of the 593 \nsuspension was mixed with 40 μ l of the 5x CellROX Green solution to obtain a final reaction 594 \nvolume of 200 μ l. Samples were incubated for 2 h at 20 °C in the dark under gentle agitation to 595 \nensure uniform staining. Following incubation, animals were pelleted by centrifugation at 1000 596 \nrpm for 1 min, washed three times with fresh M9 buffer to remove residual dye, mounted on 2% 597 \nagarose pads, and imaged. 598 \n  599 \nSensitivity to stress 600 \nSensitivity to oxidative stress was assessed using H 2O2 treatment in liquid culture following 601 \nestablished protocols in C. elegans  (Offenburger & Gartner, 2018). A H 2O2 stock solution was 602 \nfreshly prepared from 30% (w/v 9.8 M) H 2O2 and diluted with water to generate a 5x stock 603 \nsolution of 50 mM. For treatment, the 5x stock was added to synchronized L1 animals 604 \nsuspended in M9 buffer to obtain the desired final concentration. Samples were incubated for 1 605 \nh at 20 °C under gentle agitation. After treatment, animals were washed three times with 1 mL 606 \nof M9 buffer to remove residual H 2O2 and transferred to OP50-seeded NGM plates for recovery. 607 \nAnimals were plated in triplicate, and developmental progression was scored 48 h post-608 \ntreatment. 609 \n 610 \nSensitivity to IR was assessed by exposing age-synchronized animals to X-ray irradiation, 611 \nfollowed by analysis of post-IR developmental progression (Ermolaeva et al., 2013). Briefly, 612 \nsynchronized animals were irradiated with a single dose of 100 Gy, transferred to OP50-seeded 613 \nNGM plates for recovery under standard conditions, and plated in triplicate. Sensitivity to IR was 614 \nquantified by scoring developmental stage 48 h post-IR, using vulval morphology and overall 615 \nbody size as staging criteria. 616 \n  617 \nLifespan, reproductive fitness, and apoptosis assays 618 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n26 \n \nAge-synchronized L4 animals from different genetic backgrounds were transferred to OP50- 619 \nseeded NGM plates and maintained under standard conditions. For lifespan analysis, groups of 620 \n20 animals were plated on each NGM plate and transferred to fresh plates daily until egg-laying 621 \nceased. Viability was assessed daily by gently prodding the head or tail with a platinum wire; 622 \nanimals unresponsive to stimulation were scored as dead. Animals that escaped, ruptured, or 623 \ndied due to internal hatching (“bagging”) were censored from the analysis, following standard 624 \nlifespan assay criteria (Kenyon et al., 1993). 625 \n  626 \nFor reproductive fitness assays, individual animals were placed on 35 mm OP50-seeded NGM 627 \nplates and transferred to fresh plates daily until egg-laying ceased. After 24 h, unhatched 628 \nembryos were scored as dead embryos, and after 48 h, live larvae were counted to determine 629 \nbrood size. Total progeny counts were analyzed and compared across genotypes, as previously 630 \ndescribed (Andux & Ellis, 2008). 631 \n  632 \nFor apoptosis assays, animals were collected at 24 h after the L4 stage, immobilized with 1 mM 633 \nlevamisole, and mounted on 2% agarose pads. Germ cell corpses in the gonad arms were 634 \nvisualized and quantified using fluorescence microscopy with the ced-1::gfp(bcIs39) reporter 635 \nstrain, as previously described (Zhou et al., 2001). To assess DNA damage-induced apoptosis, 636 \nL4 animals were exposed to IR, and apoptotic germ cells were quantified at 24 h post-IR 637 \ntreatment  (Gartner et al., 2000). 638 \n  639 \nPseudomonas survival assays 640 \nSurvival assays on P. aeruginosa  PA14 were performed as previously described (Kwon et al., 641 \n2024) with minor modifications. Briefly, PA14 was grown overnight in LB broth at 37 °C, seeded 642 \nevenly across the entire surface of NGM plates, and incubated at 37 °C for 24 h followed by an 643 \nadditional 24 h at 25 °C prior to use. Age-synchronized L4 animals were transferred to PA14-644 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n27 \n \nseeded plates supplemented with 50 μ M 5-fluoro-2’-deoxyuridine (FUDR) to prevent progeny 645 \nproduction and maintained at 25 °C. Survival was monitored every 12 h. Animals that ruptured 646 \ninternally (“bagging”), crawled off the agar, or exhibited vulval bursting were censored from the 647 \nanalysis. At least 60 animals per genotype were scored per assay, and three independent 648 \nbiological replicates were performed. 649 \n 650 \nStatistical analysis 651 \nStatistical analyses were performed using GraphPad Prism. For experiments involving two 652 \nindependent variables, data were analyzed by ordinary two-way ANOVA. When significant 653 \neffects were detected, multiple comparisons were performed using Šidak’s or Tukey’s post hoc 654 \ntests, as indicated in the figure legends. Comparisons between two independent groups were 655 \nperformed using unpaired two-tailed Student’s t-test. Survival curves were compared using log-656 \nrank (Mantel-Cox) test and the Gehan-Berslow-Wilcoxon test. All tests were two-sided. Data are 657 \npresented as mean ± SEM unless stated otherwise. A p value < 0.05 was considered 658 \nstatistically significant. 659 \n 660 \nFigure legends 661 \n 662 \nFigure 1 663 \nIR induces transcriptional activation of mul-1 in the intestine of C. elegans. 664 \n(A) Under control conditions, mul-1 expression in mul-1(syb3342) IV  animals is detected 665 \npredominantly in intestinal nuclei, with the strongest signal in the two anterior-most nuclei and a 666 \ngradual increase during larval development. 667 \n(B) Six hours after exposure to 100 Gy IR, mul-1 expression is robustly induced in intestinal 668 \nnuclei across all larval stages, initiating in the anterior cells and subsequently expanding 669 \nthroughout the gut. 670 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n28 \n \n(C) Representative fluorescence intensity profiles measured along a transverse line across the 671 \nfirst pair of anterior intestinal nuclei in mul-1(syb3342) IV animals. 672 \n(D) Quantification of nuclear fluorescence intensity derived from the maximum intensity peaks 673 \ncorresponding to each nucleus, following optimized line placement to minimize background 674 \ncontributions from adjacent intestinal cells in different focal planes. 675 \nScale bars, 20 μ m. Statistical analysis was performed using two-way ANOVA with Šidak’s 676 \nmultiple comparisons test. Quantification includes animals from at least three independent 677 \nexperiments (n = 20-30 animals per developmental stage and condition). 678 \n  679 \nFigure 2 680 \nmul-1 expression is selectively induced by IR but not by other DNA-damaging agents. 681 \nRepresentative images of mul-1(syb3342) IV animals under control (A) conditions or following 682 \nexposure to IR (B), cisplatin (C), MMS (D), or UV irradiation (E). Robust induction of mul-1 683 \nexpression in intestinal nuclei is observed specifically after IR (B) whereas other DNA-damaging 684 \nagents elicit little or no reporter activation (C-E). Animals were treated with the respective 685 \nagents at the L4 stage and assayed after 6h after IR (B) , 24h after cisplatin treatment (C), 16 686 \nhours after MMS treatment (D)  and 24hours after UV treatment (E)  (Materials and Methods). 687 \n(F) quantification of nuclear mCherry fluorescence intensity in intestinal cells under the indicated 688 \nconditions. 689 \nScale bars, 20 µm. Data are shown as mean ± SEM and include animals from at least three 690 \nindependent experiments (n = 20-30 animals per condition). Statistical analysis was performed 691 \nusing two-way ANOVA Tukey’s multiple comparisons test. 692 \n  693 \nFigure 3 694 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n29 \n \nOxidative stress, but not general stressors, triggers mul-1 induction. 695 \n(A-D) Representative images of mul-1(syb3342) IV animals subjected to starvation, heat shock, 696 \nor osmotic stress show no detectable reporter activation in intestinal nuclei. 697 \n(E) Treatment with H2O2 induces robust mul-1 expression in intestinal nuclei. 698 \n(A-E) All animals were treated at the L1 stage and imaged after 24hours (note that starved and 699 \nH2O2 treated worms are developmentally arrested. 700 \n(F-G) Basal mul-1 expression in prdx-2(gk169) II; mul-1(syb3342) IV  animals is comparable to 701 \ncontrols during early larval stages ( L1-L2). 702 \n(H-J) As development progresses, mul-1 activation in prdx-2 mutants initiates in anterior 703 \nintestinal nuclei and gradually extends toward posterior regions of the gut. 704 \n(K) Quantification of fluorescence intensity in anterior intestinal nuclei confirms selective mul-1 705 \ninduction by oxidative stress. 706 \n(L) Comparative quantification under control conditions reveals elevated basal mul-1 activation 707 \nin prdx-2 mutants. 708 \nScale bars, 20 µm. Data are shown as mean ± SEM and include animals from at least three 709 \nindependent experiments (n = 20-30 animals per condition). Statistical analysis was performed 710 \nusing two-way ANOVA followed by Tukey’s multiple comparisons test. 711 \n  712 \nFigure 4 713 \nThe p38 MAPK pathway and ATF-7, but not SKN-1, are required for mul-1 induction 714 \nfollowing IR. 715 \n(A) IR-induced mul-1 reporter expression in mul-1(syb3342) IV animals. 716 \n(B-C) Loss of the core p38 MAPK components sek-1 and pmk-1 abolishes mul-1 induction in 717 \nresponse to IR, indicating an essential role for this signaling pathway. 718 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n30 \n \n(D-E) Genetic analysis of downstream transcription factors shows that atf-7, but not skn-1 , is 719 \nrequired for IR-dependent mul-1 activation. 720 \n(F) Quantification of fluorescence intensity in anterior intestinal nuclei across genotypes and 721 \nconditions. 722 \nAnimals were treated at the L1 stage. Scale bars, 20 µm. Data are shown as mean ± SEM and 723 \ninclude animals from at least three independent experiments (n = 20-30 animals per condition). 724 \nStatistical analysis was performed using two-way ANOVA followed by Tukey’s multiple 725 \ncomparisons test. 726 \n  727 \nFigure 5 728 \nMUL-1 protein accumulates in response to IR and oxidative stress. 729 \n(A) The glo-1(zu391) X  mutation reduces intestinal autofluorescence, improving visualization of 730 \nfluorescent reporters. 731 \n(B) No detectable MUL-1 expression is observed in mul-1(gt3545) IV; glo-1(zu391) X  animals 732 \nunder control conditions. 733 \n(C-D) Following exposure to IR or H2O2 treatment, MUL-1 protein accumulates in intestinal cells, 734 \ndisplaying diffuse cytoplasmic localization and formation of cytoplasmic puncta. 735 \n(E) An integrated multicopy mul-1::eGFP transgene displays detectable basal expression in 736 \nintestinal cells under control conditions, with cytoplasmic and punctate localization, particularly 737 \nevident in anterior intestinal cells. 738 \n(F) Quantification of intestinal MUL-1 fluorescence intensity following IR exposure, measured as 739 \ncorrected total cell fluorescence (CTCF). 740 \n(G-H) Basal MUL-1 protein levels in mul-1(gt3545) IV; glo-1(zu391) X  animals at the L4 and 741 \nadult stages, intestinal MUL-1 protein signal is not readily detectable under control conditions. 742 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n31 \n \n(I-J) In contrast, prdx-2(gk169) II; mul-1(gt3545); glo-1(zu391) X  animals display detectable 743 \nintestinal MUL-1 protein accumulation at the L4 and adult stages, with cytoplasmic distribution 744 \nand punctate structures. 745 \nUnless otherwise indicated, animals were analysed at the L1 stage. Scale bars, 20 µm. Data are 746 \nshown as mean ± SEM from at least three independent experiments (n = 20-30 animals per 747 \ngenotype and condition). Statistical analysis was performed using two-way ANOVA followed by 748 \nTukey’s multiple comparisons test. 749 \n  750 \nFigure 6 751 \nMUL-1 buffers oxidative stress, promotes developmental progression under oxidative 752 \nstress, and restrains IR-induced germline apoptosis. 753 \n(A) Lifespan analysis under control conditions reveals no significant difference between wild-754 \ntype and mul-1 mutants (n = 10 animals per genotype). 755 \n(B) Brood size analysis of wild-type and mul-1(syb3342) IV animals under control conditions 756 \nshows no significant difference in total progeny (n = 10-20 animals per genotype). 757 \n(C) Embryonic viability, assessed by the fraction of hatched embryos, is comparable between 758 \nwild-type and mul-1mutants (n = 10-20 animals per genotype). 759 \n(D) Quantification of CellROX Green fluorescence intensity in wild-type and mul-1(syb3342) IV 760 \nanimals under control conditions and following IR reveals exaggerated ROS accumulation in 761 \nmul-1 mutants after IR (n = 20-30 animals per genotype and condition). 762 \n(E-F) Representative CellROX green images of wild-type animals show low basal ROS levels 763 \nunder control conditions and a moderate increase following IR. 764 \n(G-H) In contrast, mul-1(syb3342) IV animals display low basal CellROX signal under control 765 \nconditions, but accumulate excessive ROS after IR, with strong fluorescence particularly evident 766 \nin intestinal cells. 767 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n32 \n \n(I) Developmental stages distribution 48 h after exposure to 2.5 mM H 2O2 at the L1 stage (n = 768 \n60 animals per genotype). Developmental stages were scored based on vulval morphology and 769 \noverall body size. mul-1 (syb3342) IV  mutants display a moderate delay in developmental 770 \nprofession compared to wild-type animals, comparable to that observed in daf-16 and pmk-1  771 \nmutants, which were included as positive controls for oxidative stress sensitivity. 772 \n(J) Quantification of germ cell corpses 24 h after exposure to IR reveals a hyperinduction of 773 \napoptosis in mul-1  mutants, which is suppressed in cep-1; mul-1  double mutants (n = 20-30 774 \nanimals per genotype and condition). This phenotype was independently confirmed using a mul-775 \n1(STOP-IN) null allele. Germ cell corpses were scored using the ced-1::gfpreporter. 776 \nL1 animals were analysed unless otherwise indicated. Scale bars, 20 µm. Data are shown as 777 \nmean ± SEM from at least three independent experiments. Lifespan (A) was analyzed using log-778 \nrank (Mantel-Cox) and Gehan-Breslow-Wilcoxon tests. Brood size and embryonic viability (B-C) 779 \nwere analyzed using unpaired two-tailed Student’s t-tests. CellROX fluorescence (D) and germ 780 \ncell apoptosis (J) were analyzed by two-way ANOVA followed by Tukey’s or Šidak’s multiple 781 \ncomparisons tests. 782 \n  783 \nFigure 7 784 \nA ShKT-containing MUL-1 paralog cluster acts redundantly to maintain germline 785 \nhomeostasis and enable developmental recovery after IR. 786 \n(A) Schematic representation of the domain architecture of MUL-1 and its closest paralogs, all 787 \nencoding ShKT domain-containing proteins. 788 \n(B) Pairwise sequence identity matrix comparing MUL-1 and related paralogs. 789 \n(C) Schematic representation of the F49F1 genomic locus on chromosome IV showing the 790 \norganization of mul-1  and its paralogs. The syb8776 allele corresponds to a deletion of an 791 \napproximately 7.9 kb region encompassing all four genes. 792 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n33 \n \n(D) Lifespan analysis of F49F1 quadruple mutant shows no significant difference compared to 793 \nwild-type under control conditions (n = 10-20 animals per genotype). 794 \n(E) Progeny production is significantly reduced in the F49F1 quadruple mutant (n = 10-20 795 \nanimals per genotype). 796 \n(F) Embryonic lethality remains unchanged in F49F1 quadruple mutants (n = 10-20 animals per 797 \ngenotype). 798 \n(G) Germ cell apoptosis is elevated in the F49F1 quadruple mutants under both control and IR 799 \nconditions (n = 20-30 animals per condition). 800 \n(H) Developmental stage distribution of animals exposed to IR at the L1 stage and scored after 801 \n48 hours recovery (n = 60 animals per genotype). 802 \nData are shown as mean ± SEM. Lifespan analyses (D) were performed using log-rank (Mantel-803 \nCox) and Gehan-Breslow-Wilcoxon tests. Progeny production and embryonic viability (E-F) 804 \nwere analyzed using unpaired two-tailed Student’s t-tests. Germ cell apoptosis (G) was 805 \nanalyzed by two-way ANOVA followed by Tukey’s multiple comparisons test. 806 \n  807 \nFigure 8  808 \nRedundant MUL-1 paralogs contribute to resistance against P. aeruginosa infection. 809 \n(A) Survival analysis of wild-type animals, mul-1(syb3342) IV , pmk-1 and the F49F1 mutants 810 \nfollowing exposure to P. aeruginosa PA14. While mul-1 single mutants do not display increased 811 \nsensitivity, the quadruple mutant exhibits reduced survival comparable to the pmk-1 positive 812 \ncontrol (n = 60 animals per genotype). 813 \n(B-C) Representative images showing reporter expression in adult animals exposed to E. coli 814 \nOP50 (B) or P. aeruginosaPA14 (C). 815 \n(D) Quantification of fluorescence intensity reveals robust induction of mul-1 reporter expression 816 \nupon PA14 exposure compared to OP50-fed controls. 817 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n34 \n \nData are shown as mean ± SEM from three independent experiments. Fluorescence intensity 818 \n(D) was analyzed using an unpaired two-tailed Student’s t-test with Welch’s correction. 819 \n  820 \nFigure 9 821 \nMUL-1 paralogs restrain basal ROS accumulation. 822 \nRepresentative images of wild-type (A) and F49F1(syb8776) IV  animals (B) stained with 823 \nCellROX Green under control conditions. 824 \n(C) Quantification of fluorescence intensity reveals increased basal ROS levels in the quadruple 825 \nmutant compared to wild-type animals (n = 20 animals per genotype). 826 \nData are shown as mean ± SEM from at least three independent experiments. Statistical 827 \nanalysis was performed using an unpaired two-tailed Student’s t-test with Welch’s correction. 828 \n  829 \nFigure 10 830 \nCompensatory induction of GST-4::mCherry and SOD-3::eGFP. 831 \n(A) Expression pattern of the oxidative stress reporters gst-4::mCherry and sod-3::eGFP in wild-832 \ntype L1 larvae carrying the glo-1(zu391) X mutation. gst-4::mCherry is predominantly expressed 833 \nin the intestine, whereas sod-3::eGFP localizes mainly to the pharynx. 834 \n(B) Deletion of mul-1 alone does not alter gst-4 or sod-3 expression. 835 \n(C) The quadruple mutant shows strong induction of gst-4 throughout the body, particularly in 836 \nthe anterior intestine, together with widespread upregulation of sod-3. 837 \n(D) prdx-2(gk169) II mutants exhibit robust induction of gst-4  and increased sod-3 expression, 838 \nconsistent with elevated endogenous oxidative stress. 839 \n(E) Induction of gst-4 in prdx-2 mutants requires skn-1. 840 \n(F) Induction of sod-3 in prdx-2 mutants is abolished in the absence of daf-16. 841 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n35 \n \nRepresentative images are shown. Quantification of gst-4::mCherry and sod-3::eGFP  842 \nfluorescence was performed on 20-30 animals per genotype per experiment. Data are shown as 843 \nmean ± SEM from at least three independent experiments. Statistical analysis was performed 844 \nusing one-way ANOVA followed by Tukey’s multiple comparisons test. 845 \n  846 \nFigure 11 847 \nGenetic interactions between MUL-1 and its paralogs shape organismal responses to 848 \noxidative and genotoxic stress. 849 \n(A) Suppression of apoptosis defect of sysm-1. 850 \n(B) Genetic interaction with the F46B3.1 MUL-1 paralog. 851 \n(C) Suppression of H2O2 sensitivity by F46B3.1 loss-of-function. 852 \n(D) Suppression of Pseudomonas PA14 sensitivity by F46B3.1 loss-of-function. 853 \n(E) F46B3.1 loss-of-function increases sensitivity to IR.  854 \nData are shown as mean ± SEM from at least three independent experiments. Germ cell 855 \napoptosis (A) was analyzed by two-way ANOVA followed by Tukey’s multiple comparisons test 856 \n(n = 20-30 animals per condition). H 2O2 and IR sensitivity assays (C, E) were analyzed by two-857 \nway ANOVA (n = 60 animals per genotype). Survival assays (D) were analyzed using log-rank 858 \n(Mantel-Cox) tests (n = 60 animals per genotype). 859 \n 860 \nFigure 12 861 \nModel for the integration of DNA damage and redox signaling by MUL-1 and ShKT 862 \ndomain proteins. 863 \nIR increases ROS, engaging the SEK-1/PMK-1 p38 MAPK pathway and its downstream 864 \ntranscription factor ATF-7 to induce MUL-1 and other ShKT-domain proteins. Under 865 \nphysiological conditions, PRDX-2 limits basal ROS levels. Upon stress, ShKT proteins function 866 \nas redox-responsive modulators that limit the magnitude of antioxidant gene activation. In 867 \nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\n36 \n \nparallel, elevated ROS activate SKN-1/Nrf2 to promote GST-4 expression and DAF-16/FoxO to 868 \ndrive SOD-3 expression. In the absence of ShKT proteins, derepression of GST-4 and SOD-3 869 \nenhances antioxidant c apacity, thereby supporting genome stability and normal development 870 \nwhile mitigating p53/CEP-1-dependent germ cell apoptosis. 871 \n 872 \n 873 \nReferences 874 \nAndux, S., & Ellis, R. E. (2008). Apoptosis maintains oocyte quality in aging Caenorhabditis 875 \nelegans females. PLoS Genetics, 4(12), e1000295. 876 \nAranda-Rivera, A. K., Cruz-Gregorio, A., Arancibia-Hernández, Y. L., Hernández-Cruz, E. Y., & 877 \nPedraza-Chaverri, J. (2022). RONS and oxidative stress: An overview of basic concepts. 878 \nOxygen, 2(4), 437–478. 879 \nBlackwell, T. K., Steinbaugh, M. J., Hourihan, J. 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Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\nFig 1\nDICmCherryMerge\nL1 L2 L3 L4 Adult\nControl\nDICmCherryMerge\nIR\nA\nB\nC\nD\nL1 L2 L3 L4 Adult\n0 10 20 30\n0\n200\n400\n600\n800\nDistance (um)\nFluorescence intensity\n(a.u.)\nL1 Control\nIR\n0 10 20 30\n0\n200\n400\n600\n800\nL2\nDistance (um)\n0 10 20 30\n0\n200\n400\n600\n800\nDistance (um)\nL3\n0 10 20 30 40\n0\n200\n400\n600\n800\nDistance (um)\nL4\n0 10 20 30 40\n0\n200\n400\n600\n800\nDistance (um)\nAdult\nL1 L2 L3 L4Adult\n0\n200\n400\n600\n800\nFluorescence intensity\n(a.u.)\nControl\nIR\nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\nFig 2\nMMS\nDICmCherryMerge\nUVControl Cisplatin\nIR\nA B C D E\nF\nControl\nDNA damaging agent\nIR\nCisplatin MMS UV\n0\n200\n400\n600\n800\nFluorescence intensity\n(a.u.)\nns ns\nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\nFig 3\nDIC\nmCherryMerge\nL1 L2 L3 L4 Adult\nprdx-2(gk169) II; mul-1(syb3342) IV\nF G I J\nDICmCherryMerge\nStarvation Heat shock Oxidative\nA B C D E\nControl Osmotic\nH\nK L\nStarvationHeat shockOsmoticOxidative\n0\n200\n400\n600\n800\nFluorescence intensity\n(a.u.)\nns ns ns\nL1 L2 L3 L4Adult\n0\n200\n400\n600\n800\n1000\n1200\n1400\nFluorescence intensity\n(a.u.)\nmul-1(syb3342)  IV\nprdx-2(gk169)III;\nmul-1(syb3342) IV\nControl\nStress\nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\nFig 4\nDICmCherryMerge\nmul-1(syb3342) IV\nmul-1(syb3342)\npmk-1(km25) IV\natf-7(qd221qd130) III;\nmul-1(syb3342) IV\nmul-1(syb3342) IV;\nsek-1(km4) X\nmul-1(syb3342)\nskn-1(zj15) IV\nA B C D E\nF\nmul-1(syb3342) IV \nsek-1(km4) Xpmk-1(km25) IV skn-1(zj15) IV\natf-7(qd22qd130) III\n0\n200\n400\n600\n800\nFluorescence intensity\n(a.u.)\nns ns\nControl\nIR\nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\nDICeGFPMerge\nControl\nglo-1(zu391) X\nmul-1(gt3545) IV;\nglo-1(zu391) X\nControl IR\n Oxidative\nprdx-2(gk169) II;\nmul-1(gt3545) IV;\nglo-1(zu391) X\nA B C D\nF\nJ\nAdult\nmul-1(gt3545) IV;\nglo-1(zu391) X\nL4\nG H\nI\nDIC eGFP DIC eGFP\nmul-1(gtIs3000)\nlin-15 (+)\nE\nControl\nFig 5\nglo-1(zu391) Xmul-1(gt3545) IV;\nglo-1(zu391) X\n0\n2 105\n4 105\n6 105\nCTCF (a.u.)\nns\nns\nControl\nIR\nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\nFig 6\nmul-1(syb3342) IV\nIRControl\nWild-type\nIRControl\nDICmCherryCellROX\nE F G H\nA B\nC D\n0 5 10 15 20\n0\n20\n40\n60\n80\n100\nDays post-L4\nSurvival (%)\nWild-type\nmul-1(syb3342) IV\nWild-type\nmul-1(syb3342) IV\n0\n20\n40\n60\n80\n100Hatching embryos (%)\nns\nWild-type\ndaf-16(mu86) Ipmk-1(km25) IVmul-1(syb3342) IV \n0\n20\n40\n60\n80\n100% of individuals\n2.5 mM H2O2\nL4\nL3\nL2\nL1\nced-1::gfp(bcIs39) V\ncep-1(lg12501) Imul-1(syb3342) IVmul-1(gt3459) IVcep-1(lg12501) I;\nmul-1(syb3342) IV\n0\n5\n10\n15\n20\n25\n30germ cell corpses/ gonad arm\nns\nControl\nIR\nWild-type\nmul-1(syb3342) IV\n0.0\n5.0 105\n1.0 106\n1.5 106\n2.0 106\nCTCF (a.u.)\nns\nControl\nIR\nI J\nWild-type\nmul-1(syb3342) IV\n0\n100\n200\n300Brood size\nns\nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\nFig 7\nA B\nD E F\nG\nMUL-1A Signal ShKT ShKT ShKT ShKT ShKT\nMUL-1B ShKT ShKT ShKT ShKT\nDRD-50 Signal ShKT ShKT ShKT ShKT ShKT\nF49F1.7A Signal ShKT ShKT ShKT ShKT\nF49F1.5A Signal ShKT ShKT ShKT\nMUL-1A\nMUL-1B\nDRD-50\nF49F1.5A\nF49F1.7A\nResidues Query Cover\n(%)\nIdentity\n(%) Signal Peptide ShKT Domains\n259\n189\n189\n265\n159\n100\n72\n98\n48\n96\n100\n100\n49\n50\n32\n+\n-\n+\n+\n+\n5\n4\n5\n4\n3\n0 5 10 15 20\n0\n20\n40\n60\n80\n100\nDays post-L4\nSurvival (%)\nWild-type F49F1(syb8776) IV\nWild-type\nF49F1(syb8776) IV\n0\n100\n200\n300Brood size\nWild-type\nF49F1(syb8776) IV\n0\n20\n40\n60\n80\n100Hatching embryos (%)\nWild-type\npmk-1(km25) IVmul-1(syb3342) IV F49F1(syb8776) IV\n0\n20\n40\n60\n80\n100% of individuals\nIR\nL4\nL3\nL2\nL1\nH\nced-1::gfp(bcIs39) V\ncep-1(lg12501)I\nF49F1(syb8776) IVcep-1(lg12501)I;\nF49F1(syb8776)IV\n0\n5\n10\n15\n20\n25\n30\ngerm cell corpses/ gonad arm\nns\nns\nns\nControl\nIR\nmul-1a\n5000 bp\nmul-1bF49F1.5b\nF49F1.5adrd-50 F49F1.7a\nF49F1.7b\n10000 bp\nsyb8776\nC\nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\nFig 8\nBrightfieldmCherryMerge\nOP50 PA14\nB C\nD\nA\nOP50 PA14\n0\n20000\n40000\n60000\nFluorescence intensity\n(a.u.)\n0 12 24 36 48 60\n0.0\n0.2\n0.4\n0.6\n0.8\n1.0\nTime (h)\nSurvival on PA14 (%)\nWild-type pmk-1(km25) IV\nmul-1(syb3342) IV F49F1(syb8776) IV\nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\nFig 9\nWild-type\nDICeGFPMerge\nF49F1(syb8776) IV\nWild-type\nF49F1(syb8776) IV\n0\n200000\n400000\n600000\n800000\nCTCF (a.u.)\nA B C\nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\nFig 10\nDIC\ndaf-16(mu86) I;\nprdx-2(gk169) II;\ngst-4::mCherry;\nsod-3::egfp\nglo-1(zu391) X\nF\nprdx-2(gk169) II;\nskn-1(zj15)\ngst-4::mCherry IV;\nsod-3::egfp\nglo-1(zu391) X\nE\nprdx-2(gk169) II;\ngst-4::mCherry IV;\nsod-3::egfp\nglo-1(zu391) X\nD\nF49F1(gt3613)\ngst-4::mCherry IV;\nsod-3::egfp\nglo-1(zu391) X\nC\nmul-1(gt3625)\ngst-4::mCherry IV;\nsod-3::egfp\nglo-1(zu391) X\nB\neGFP mCherry\ngst-4::mCherry IV;\nsod-3::egfp\nglo-1(zu391) X\nMerge\nA\ngsg\nmul-1; gsgF49F1; gsgprdx-2; gsg\nprdx-2; skn-1; gsgdaf-16; prdx-2; gsg\n0\n2 x 105\nCTCF (a.u.)\nns\nns\nmCherry\n4 x 105\n6 x 105\n8 x 105\n1 x 106\ngsg\nmul-1; gsgF49F1; gsgprdx-2; gsg\nprdx-2; skn-1; gsgdaf-16; prdx-2; gsg\n0\nCTCF (a.u.) ns\nns\nns\neGFP\n2 x 106\n4 x 106\n6 x 106\ngst-4::mCherry IV;\nsod-3::egfp\nglo-1(zu391) X\ngsg\n{\nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\nFig 11\nA B\nD\nC\nE\n0 12 24 36 48 60\n0.0\n0.2\n0.4\n0.6\n0.8\n1.0\nTime (h)\nSurvival on PA14 (%)\npmk-1(km25) IV\nF49F1(syb8776) IV F49F1(syb8776) IV;\nF46B3.1(syb8669) V\nWild-type Wild-type\npmk-1(km25) IVF49F1(syb8776) IVF49F1(syb8776) IV;\nF46B3.1(syb8669) V\n0\n20\n40\n60\n80\n100% of individuals\nIR\nL4\nL3\nL2\nL1\nWild-type\ndaf-16(mu86) Ipmk-1(km25) IVF49F1(syb8776) IVF49F1(syb8776) IV;\nF46B3.1(syb8669) V\n0\n20\n40\n60\n80\n100% of individuals\n2.5 mM H2O2\nL4\nL3\nL2\nL1\nWild-type\nF49F1(syb8776) IV;\nF46B3.1(syb8669) V\n0\n100\n200\n300Brood size\nns\n0\n5\n10\n15\n20\n25\n30\ngerm cell corpses/ gonad arm\nns\nns\nControl\nIR\nced-1::gfp(bcIs39) Vsysm-1(ok3236) IIsysm-1(ok3236) II;\nmul-1(syb3342) IV\nsysm-1(ok3236) II;\nF49F1(syb8776) IV\nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint \n\nFig 12\nIonizing radiation\nROS\nSEK-1/SEK\nPMK-1/p38\nATF-7/ATF2/ATF7/CREB\nMUL-1/ShKT Proteins\nSKN-1/Nrf2\nGST-4/GSTP1\nPRDX-2/PRDX1/PRDX2\nDAF-16/FoxO\nSOD-3/SOD3\nGenome stability, Development\np53-dependent germ cell apoptosis\nS-S S-S\nS-S\nremix, or adapt this material for any purpose without crediting the original authors. \npreprint (which was not certified by peer review) in the Public Domain. It is no longer restricted by copyright. Anyone can legally share, reuse, \nThe copyright holder has placed thisthis version posted May 7, 2026. ; https://doi.org/10.64898/2026.05.03.722560doi: bioRxiv preprint","source_license":"Public-Domain","license_restricted":false}