CONICET | Buscador de Institutos y Recursos Humanos

Terrestrial life evolved only after the stratospheric ozone layer formed and could absorb most damaging UV-B (280-315 nm) in solar radiation. Because plants must absorb photons to power photosynthesis, they are inevitably exposed to damaging UV-B. Chromatin remodeling in response to UV-B has been implicated in maize: transgenic plants expressing RNAi to reduce four chromatin factors were found to be acutely sensitive to UV-B at doses that do not cause visible damage to normal maize. Therefore, chromatin remodeling capacity appears to be a key process in maize for effective responses to UV-B. ChIP assays were done to monitor chromatin status at several UV-B responsive genes in tolerant and sensitive lines: the promoter and transcribed regions of UV-B up-regulated genes in tolerant lines showed different chromatin protein association after UV-B than sensitive lines, including transgenic plants expressing RNAi against the chromatin remodeling genes chc101 and mbd101. Transcriptome analysis on chc101 and mbd101 RNAi-mediated knockdown maize lines after UV-B treatments was also done. These RNAi lines exhibit substantially different transcriptome changes compared to each other and to UV-B tolerant non-transgenic siblings. By functional analysis, the largest category of genes with predicted functions affected by UV-B in both lines was the DNA/chromatin binding category. Differential activation of suites of transcription factors in the control and transgenic lines are the likely explanation for the discrete transcriptome profiles. With the increasing number of examples of epigenetic gene regulation, the chromatin status and remodeling capacity of a line are key phenotypes that determine the ability to express genes and the rapidity with which changes in expression can be accomplished. Our results indicate that chromatin remodeling is a key process in acclimation to UV-B treatment and that lines deficient in this process are more sensitive to UV-B.