UV-B effect on DNA mismatch repair proteins

LARIO, L.; CLAUDIA PATRICIA SPAMPINATO; CASATI, P.

Campinhas

Congreso; VIII CAEB; 2007

CAEB

Plant DNA is continuously damaged by ultraviolet (UV) irradiation. Plants generally have a higher tolerance for UV than animals due to the absorption of UV by waxy substances on leaf surfaces, cell walls and intracellular chemical compounds such as flavonoids. However, UV radiation that is not absorbed induces DNA damage that should be repaired to maintain genetic stability. Different DNA repair mechanisms exist that are both specific and overlapping.  Mismatch repair (MMR) systems repair DNA mismatches and participate in responses to a variety of adducts induced by endogenous and exogenous agents. The MMR system functions through the interactions between several proteins, such as MSH2, MSH6, MLH1 and PMS1. Besides these proteins plants also encode a unique MSH7. To investigate the regulation of plant MMR by UV-B, we evaluated the transcripts levels of MMR proteins by qRT-PCR. Our results demonstrate that MSH2, MSH6 and PMS1 mRNAs are induced by UV-B in A. thaliana leaves and flowers, while MLH1 remained unchanged in these tissues. A similar effect was observed for MSH2 and MSH6 from Z. mays. Interestingly, MSH7 mRNA levels in controls plants of both species were undetectable, while rapid induction was observed after UV-B irradiation. The correlation with protein expression and the effect of mutations in those genes in Arabidopsis using SALK-lines are under progress.