miRNA408 and its encoded peptide, miPEP408, regulate arsenic stress response in Arabidopsis

ABSTRACT MicroRNAs (miRNAs) are small non-coding RNAs that play a central role in regulating various developmental and biological processes. The expression of miRNAs is differentially modulated in response to various stresses. Based on the recent findings, it has been shown that some of the pri-miRNAs encode small regulatory peptides, microRNA-encoded peptides (miPEP). miPEPs are reported to regulate the growth and development of plants by modulating corresponding miRNA expression; however, the role of these peptides in different stresses has not been explored yet. Here, we reported that pri-miR408 encodes a small peptide, miPEP408, that regulates the expression of miR408, its targets, and associated phenotype in Arabidopsis . Plants overexpressing miR408 showed severe sensitivity under low sulphur (LS), Arsenite As(III) and LS+As(III) stress, while miR408 mutant developed through the CRISPR/Cas9 approach showed tolerance. Transgenic lines showed phenotypic alteration and modulation in the expression of genes involved in the sulphur reduction pathway and affect sulphate and glutathione accumulation. Similar to miR408 overexpressing lines, the exogenous application of synthetic miPEP408 or miPEP408 overexpression led to sensitivity in plants under LS, As(III) and combined LS+As(III) stress compared to control. This study suggests the involvement of miR408 and miPEP408 in heavy metal and nutrient deficiency responses. One-sentence summary miR408 and peptide encoded by miR408, miPEP408, regulate arsenic stress and low sulphur responses in Arabidopsis.