Role of proteins involved in miRNAs biogenesis in response to UV-B radiation in Arabidopsis thaliana plants

MARÍA LUJÁN SHERIDAN; PAULA CASATI

Congreso; XXXIV Reunión Argentina de Fisiología Vegetal; 2023

UV-B radiation generates harmful effects on plants. Because of this, plants have developed multiple mechanisms of tolerance and adaptation to UV-B. In proliferating leaves, the reduction in leaf area is in part a result of the inhibition of cell proliferation mediated by miR396, a microRNA that downregulates the expression of Growth regulating (GRFs) transcription factors. These TFs regulate numerous developmental processes acting redundantly. miR396 is expressed at low levels and increases during organ development, whereas GRFs are expressed in an opposite way. miRNAs are short RNA molecules that control gene expression at the post-transcriptional level by targeting the cleavage of complementary mRNAs or by inhibiting their translation. In plants, miRNAs precursors are transcribed by RNA polymerase II. Then, the endonuclease DCL1 participates in early stages of pri-miRNA maturation, while HYL1 and SE forms a nuclear complex with DCL1 for precise and efficient cleavage of pri-miRNAs. Finally, the nuclear protein HEN1 specifically methylates miRNA:miRNA* duplexes. In this work, we analyzed the participation of HYL1, SE and HEN1, in the response of Arabidopsis thaliana roots to UV-B exposure. For this, plants were irradiated with UV-B during 1h 5 days after stratification, and then they were allowed to grow in the absence of UV-B. The studies were carried out using WT lines, and lines deficient in microRNA processing pathway (hyl1-2, se-1 and hen1-8). Root growth rate was analyzed by monitoring primary root elongation, and by means of confocal microscopy, analyzing the number of meristematic dead cells after exposure, and also the length and number of cells in the meristematic and elongation zones. The results show that all lines show differences in at least one of the parameters analyzed, indicating that proteins involved in the biosynthetic pathways of miRNAs modulate the response of roots to UV-B radiation, acting in the development of the meristematic zone.