miR396 Repression of GRFs Inhibits Cell Proliferation by UV-B Radiation in Arabidopsis thaliana Leaves

ROMINA CASADEVALL; RAMIRO RODRIGUEZ VIRASORO; JUAN MANUEL DEBERNARDI; JAVIER PALATNIK; PAULA CASATI

Congreso; 24th Internacional Conference on Arabidopsis Research; 2013

Because of their sessile lifestyle, plants are continuously exposed to solar UV-B radiation. Inhibition of leaf growth is one of the most consistent responses of plant exposure to UV-B. In this work, we have investigated the role of GROWTH-REGULATING FACTORS (GRFs) and of microRNA miR396 in UV-B-mediated inhibition of leaf growth in Arabidopsis thaliana plants. We demonstrate that miRNA396 is up-regulated by UV-B radiation in proliferating tissues and that this induction is correlated with a decrease in GRF1, GRF2 and GRF3 transcripts. Induction of miR396 results in inhibition of cell proliferation, and this outcome is independent of the UV-B photoreceptor UVR8.   Transgenic plants expressing an artificial target mimic directed against miRNA396 (MIM396) to decrease the endogenous miRNA activity or plants expressing miRNA396-resistant copies of several GRFs are less sensitive to this inhibition.  Consequently, at intensities that can induce DNA damage in Arabidopsis plants, UV-B inhibits leaf growth by inhibiting cell division in proliferating organs, a process mediated by miR396 and GRFs.