Abstract
The genome of plants is organized into chromatin, affecting the rates of transcription, DNA recombination, and repair. In this work, we have investigated the consequences of reduced expression of some chromatin-remodeling factors and histone acetylation in maize (Zea mays) and Arabidopsis (Arabidopsis thaliana) in their participation in DNA repair after ultraviolet (UV)-B irradiation. Plants deficient in NFC102/NFC4 or SDG102/SDG26 showed more damaged DNA than wild-type plants; however, the Arabidopsis chc1 mutant showed similar accumulation of cyclobutane pyrimidine dimers as wild-type plants, in contrast to the increased DNA damage measured in the maize chc101 RNA interference line. In Arabidopsis, plants deficient in chromatin remodeling are also affected in the accumulation of pigments by UV-B. Plants treated with an inhibitor of histone acetyltransferases, curcumin, previous to the UV-B treatment show deficiencies in DNA repair; in addition, the chromatin remodeling-deficient plants have altered levels of acetylated histones after the UV-B treatment, demonstrating that histone acetylation is important during DNA repair in these two plant species. Arabidopsis mutants ham1 and ham2 also showed increased DNA damage after UV-B, suggesting that the role of these proteins in DNA damage repair has been conserved through evolution. However, cyclobutane pyrimidine dimer accumulation was higher in ham1 than in ham2; suggesting that HAM1 has a major role in DNA repair after UV-B. In summary, in this work, we have demonstrated that chromatin remodeling, and histone acetylation in particular, is important during DNA repair by UV-B, demonstrating that both genetic and epigenetic effects control DNA repair in plants.
Highlights
The genome of plants is organized into chromatin, affecting the rates of transcription, DNA recombination, and repair
To further investigate the role of this subset of chromatin-remodeling proteins in UV-B damage responses in plants, we looked for the Arabidopsis orthologs of chc101, nfc102, sdg102, and mbd101 to test if these chromatin activities in DNA repair are conserved between plant species
For NFC102, the BLAST analysis resulted in the identification of an Arabidopsis homolog, NFC4, known as MSI4/ FVE (At2g19520; Hennig et al, 2005), showing a 74% identity for the corresponding ORF and 77% identity at the protein level (Supplemental Fig. S1, C and D); and for maize SDG102, we found that Arabidopsis SDG26 or ASHH1 (At1g76710) showed the highest homology, with 43% identity for the corresponding ORF and 55% identity at the protein level (Supplemental Fig. S1, E and F)
Summary
The genome of plants is organized into chromatin, affecting the rates of transcription, DNA recombination, and repair. The nucleosomal structure is a barrier to proteins involved in transcription, replication, and DNA recombination and repair; and chromatin must be restructured in order to allow these processes to occur. The involvement of the Arabidopsis SWI2/SNF2 gene family in DNA recombination and repair has been demonstrated (Fritsch et al, 2004). Shaked et al (2006) showed that 14 of the 40 Arabidopsis SWI2/SNF2 gene family members had a role in DNA damage response against g or UV-C radiation and recombination. All these results have demonstrated the participation of chromatin remodeling in DNA repair and recombination in different species. Mutations that are lethal in other species are viable in plants, like RAD50 (Gallego and White, 2001), MRE11 (Gallego et al, 2001; Bundock and Hooykaas, 2002), or AtERCC1 (Hefner et al, 2003; Dubest et al, 2004)
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