Methyl-CpG binding domain protein acts to regulate the repair of cyclobutane pyrimidine dimers on rice DNA.

UVB radiation causes cyclobutane pyrimidine dimers (CPDs) to form on the DNA of living organisms. This study found that overexpression of the silicon absorbance gene Lsi1 reduced the accumulation of CPDs in rice, which profited from the reactivation by photolyase. The transcript abundance of deoxyribodipyrimidine photolyase (Os10g0167600) was generally correlated with the silicon content of the rice, and the up-regulation of Os10g0167600 was found to be highest in the UVB-treated Lsi1-overexpressed (Lsi1-OX) rice. A trans-acting factor, methyl-CpG binding domain protein (OsMeCP), was found to interact with the cis-element of Os10g0167600. The nucleic location of OsMeCP effectively enabled the transcriptional regulation. Compared with the WT, the level of OsMeCP was lower in the Lsi1-OX rice but higher in the Lsi1-RNAi line. Rice cultured in a high silicate-concentration solution also exhibited less OsMeCP abundance. Overexpression of OsMeCP led to lower Os10g0167600 transcript levels and a higher CPD content than in the WT, but the reverse was true in the OsMeCP-RNAi line. These findings indicate that OsMeCP acts as a negative regulator of silicon, and can mediate the repression of the transcription from Os10g0167600, which inhibits the photoreactivation of the photolyase involved in the repair of CPDs.