e2Fc and e2Fb transcription factors independently regulate plant growth under UV-B conditions in Arabidopsis thaliana

CASATI, PAULA; GOMEZ, M SOL; FALCONE FERREYRA, MARÍA LORENA; SHERIDAN, MARÍA LUJÁN

Barcelona

Congreso; 3. ESP-IUPB World Congress; 2019

UV-B radiation inhibits plant growth, and this inhibition is, to a certain extent, regulated by the activity of the E2Fe transcription factor. E2Fe is a target of regulation by two transcription factors from the same family, E2Fb and E2Fc. While E2Fc acts as a repressor, E2Fb is a transcriptional activator of E2Fe. Therefore, we investigated if the modulation of UV-B responses by E2Fe is through its regulation by E2Fb and/or E2Fc. We found that, at UV-B intensities that induce DNA damage, inhibition of cell proliferation is regulated by both E2Fc and E2Fb. E2Fc controls leaf size under UV-B regulating DNA damage responses, as E2Fc defcient plants show decreased programmed cell death in the roots after exposure and altered SOG1 and ATR expression. Moreover, E2Fc has an epistatic role over the miR396 pathway under UV-B, which also regulates leaf growth under these conditions. On the other hand, although E2Fb also controls cell proliferation under UV-B conditions; it does not regulate programmed cell death in the roots after exposure. Interestingly, E2Fb defcient leaf cells have increased DNA ploidy levels after UV-B exposure, similarly as E2Fe defcient cells. Together, our results demonstrate that E2Fc is required for miR396 activity on cell proliferation under UV-B, and that its role is independent of E2Fe, probably modulating DNA damage responses through the regulation of SOG1 and ATR levels. On the contrary, the regulation of DNA ploidy in leaf cells under UV-B previously described in E2Fe defcient plants could be regulated by E2Fb activity