Repression of GRFs mediated by MPK3 Inhibits Cell Proliferation by UV-B Radiation in Arabidopsis thaliana Leaves

CASADEVALL, R; RODRIGUEZ, RE; DEBERNARDI, JM; PALATNIK, JF; CASATI, P

PLANT CELL

AMER SOC PLANT BIOLOGISTS

Lugar: Rockville; Año: 2013 p. 1 - 14

1040-4651

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 plants upon exposure to UV-B radiation. In this work, we investigated the role of GROWTHREGULATING FACTORs (GRFs) and of microRNA miR396 in UV-B?mediated inhibition of leaf growth in Arabidopsis thaliana plants. We demonstrate that miRNA396 is upregulated 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 UV resistance locus 8, as well as ATM AND RAD3?RELATED and the mitogen-activated protein kinase MPK6, but is dependent on MPK3. Transgenic plants expressing an artificial target ½AQ4 mimic directed against miR396 (MIM396) decrease the endogenous microRNA activity or plants expressing miR396-resistant copies of several GRFs are less sensitive to this inhibition. consequently, at intensities that can induce DNA damage in Arabidopsis plants, UV-B radiation limits leaf growth by inhibiting cell division in proliferating tissues, a process mediated by miR396 and GRFs.