UV-B regulation of plant growth by E2F transcription factors in Arabidopsis thaliana

MARÍA SOL GOMEZ; MARÍA DEL LUJAN SHERIDAN; MARÍA LORENA FALCONE-FERREYRA; PAULA CASATI

Congreso; Plant Biology 2019; 2019

Plant growth is regulated by environmental conditions, including UV-B radiation. UV-Binhibits leaf and root growth, and inhibition of plant growth is, in part, regulated by the E2Fetranscription factor. E2Fe is a target of regulation by two transcription factors from the samefamily, E2Fb and E2Fc. While E2Fc acts as a repressor, E2Fb is a transcriptional activatorof E2Fe. Therefore, we investigated if the modulation of UV-B responses by E2Fe isthrough its regulation by E2Fb and/or E2Fc. At UV-B intensities that produce DNA damage,inhibition of cell proliferation is regulated by both E2Fc and E2Fb. E2Fc controls plantgrowth under UV-B conditions regulating DNA damage responses, as E2Fc deficient plantsshow decreased programmed cell death in the roots after exposure and altered SOG1 andATR expression. In addition, E2Fc has an epistatic role over the miR396 pathway under UVB,which also regulates leaf growth under these conditions. In contrast, while E2Fb alsocontrols cell proliferation under UV-B conditions; it does not regulate programmed cell deathin the roots after exposure. Interestingly, E2Fb deficient leaf cells have increased DNAploidy levels after UV-B exposure, similarly as E2Fe deficient cells. Together, our resultsdemonstrate that E2Fc is required for miR396 activity on cell proliferation under UV-B, andthat its role is independent of E2Fe, probably modulating DNA damage responses throughthe regulation of SOG1 and ATR levels. On the contrary, the regulation of DNA ploidy in leafcells under UV-B previously described in E2Fe deficient plants could be regulated by E2Fbactivity.