PIF4-mediated regulation of H2O2 homeostasis controls Arabidopsis seedling thermomorphogenesis

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The paper studied how reactive oxygen species, specifically hydrogen peroxide (H2O2) homeostasis, contributes to Arabidopsis seedling thermomorphogenesis under high ambient temperature, using transcriptomic analyses plus pharmacological and genetic experiments. It found that high temperature strongly induces ROS-homeostasis and signaling genes and that maintaining H2O2 homeostasis is required for hypocotyl elongation. The authors identified PIF4 as a key transcriptional regulator that directly activates CAT2 and CAT3 (catalase genes) to control H2O2 levels, with CATs acting downstream of PIF4 in the same pathway; they also reported that elevated H2O2 lowers PIF4 protein abundance, forming a PIF4–CAT–H2O2 module that integrates with auxin signaling to tune elongation. This paper does not explicitly discuss endometriosis or adenomyosis; it was included in the corpus via a keyword match in the upstream search index.

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Abstract

Summary Thermomorphogenesis under high ambient temperature involves extensive developmental changes, including hypocotyl elongation at the seedling stage, in Arabidopsis. Reactive Oxygen Species (ROS), particularly hydrogen peroxide (H 2 O 2 ), are important signaling molecules, playing crucial roles in plant development and stress responses. While ROS-homeostasis is shown to be crucial for maintaining cellular functions and mediating various developmental responses, the involvement of ROS-homeostasis in the regulation of thermomorphogenic responses and the underlying genetic basis remains poorly understood. In this study, comprehensive transcriptomic analyses revealed strong induction of ROS homeostasis and signaling genes in Arabidopsis seedlings under high ambient temperature. Pharmacological and genetic experiments showed that maintaining H 2 O 2 homeostasis is crucial for seedling thermomorphogenesis. We identified PHYTOCHROME INTERACTING FACTOR 4 (PIF4) as a key regulator of H 2 O 2 homeostasis via direct transcriptional activation of CAT2 and CAT3 genes, which are involved in the regulation of H 2 O 2 levels, to modulate hypocotyl elongation under high temperature. Genetic and biochemical experiments confirmed that CATs act downstream to PIF4 in the same signaling pathway to regulate high-temperature-responsive hypocotyl elongation. Interestingly, elevated H 2 O 2 levels reduced PIF4 protein abundance under high temperature. Together, our findings establish a PIF4-CAT-H 2 O 2 regulatory module, functioning alongside the canonical PIF4-Auxin module, that integrates to auxin signaling to fine-tune hypocotyl elongation under high temperature by maintaining H 2 O 2 homeostasis. Highlights High ambient temperature significantly affects ROS homeostasis and signaling genes in Arabidopsis seedlings. H 2 O 2 homeostasis is crucial for high-temperature-mediated hypocotyl elongation, a signature feature of Arabidopsis thermomorphogenesis. PHYTOCHROME INTERACTING FACTOR 4 (PIF4) regulates the expression of CATALASE genes in a temperature-dependent manner to maintain H 2 O 2 levels for seedling thermomorphogenesis. Elevated H 2 O 2 level reduces PIF4 protein abundance, thus forming a PIF4-CAT-H 2 O 2 regulatory module that integrates with auxin to fine-tune hypocotyl elongation under high temperature.
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Summary Thermomorphogenesis under high ambient temperature involves extensive developmental changes, including hypocotyl elongation at the seedling stage, in Arabidopsis. Reactive Oxygen Species (ROS), particularly hydrogen peroxide (H2O2), are important signaling molecules, playing crucial roles in plant development and stress responses. While ROS-homeostasis is shown to be crucial for maintaining cellular functions and mediating various developmental responses, the involvement of ROS-homeostasis in the regulation of thermomorphogenic responses and the underlying genetic basis remains poorly understood. In this study, comprehensive transcriptomic analyses revealed strong induction of ROS homeostasis and signaling genes in Arabidopsis seedlings under high ambient temperature. Pharmacological and genetic experiments showed that maintaining H2O2 homeostasis is crucial for seedling thermomorphogenesis. We identified PHYTOCHROME INTERACTING FACTOR 4 (PIF4) as a key regulator of H2O2 homeostasis via direct transcriptional activation of CAT2 and CAT3 genes, which are involved in the regulation of H2O2 levels, to modulate hypocotyl elongation under high temperature. Genetic and biochemical experiments confirmed that CATs act downstream to PIF4 in the same signaling pathway to regulate high-temperature-responsive hypocotyl elongation. Interestingly, elevated H2O2 levels reduced PIF4 protein abundance under high temperature. Together, our findings establish a PIF4-CAT-H2O2 regulatory module, functioning alongside the canonical PIF4-Auxin module, that integrates to auxin signaling to fine-tune hypocotyl elongation under high temperature by maintaining H2O2 homeostasis. Highlights High ambient temperature significantly affects ROS homeostasis and signaling genes in Arabidopsis seedlings. H2O2 homeostasis is crucial for high-temperature-mediated hypocotyl elongation, a signature feature of Arabidopsis thermomorphogenesis. PHYTOCHROME INTERACTING FACTOR 4 (PIF4) regulates the expression of CATALASE genes in a temperature-dependent manner to maintain H2O2 levels for seedling thermomorphogenesis. Elevated H2O2 level reduces PIF4 protein abundance, thus forming a PIF4-CAT-H2O2 regulatory module that integrates with auxin to fine-tune hypocotyl elongation under high temperature. Competing Interest Statement The authors have declared no competing interest.

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