Participation of chromatin remodeling proteins in UV-B responses

PAULA CASATI; LUCIANA LARIO; JULIA EMILIANI; MABEL CAMPI; VIRGINIA WALBOT; JULIA I. QÜESTA

Glasgow, Reino Unido

Congreso; Annual main meeting of the Society for Experimental Biology; 2009

Terrestrial life evolved after the ozone layer formed and couldabsorb most damaging UV-B in solar radiation. Chromatin remodelingin response to UV-B has been implicated in maize; in addition,several chromatin proteins are also UV-B regulated in Arabidopsis.Therefore, chromatin remodeling capacity appears to be a key processfor effective responses to UV-B. ChIP assays were done to monitorchromatin status at several UV-B responsive genes: the promoter andtranscribed regions in tolerant maize lines showed different chromatinprotein association after UV-B than sensitive lines. Chromatinstatus was also investigated at terminal inverted repeats of themutator transposon in maize, both in active and silencing states:reactivation by UV-B is accompanied by histone and DNA demethylation,correlating with an increase in MuRA and B transcripts. On theother hand, UV-B causes the formation of photoproducts in DNA,which affects the structural and dynamic properties of chromatin. Toinvestigate the role of different chromatin remodeling proteins inDNA repair, Arabidopsis T-DNA mutants, and maize and arabidopsisRNAi plants were analyzed. Several chromatin deficient plants (maizechc101, mbd101, sdg102 and nfc102; and Arabidopsis sdg26) showedincreased UV-B-induced DNA damage; while others (Arabidopsischc1) did not show significant differences with WT plants. On thecontrary, ros1 mutants showed increased tolerance to DNA damage,suggesting that chromatin proteins regulate different aspects of DNArepair in plants. Our results indicate that chromatin remodeling is akey process in acclimation to UV-B and that plants deficient in thisprocess are more sensitive to UV-B.