Global Genome Repair factors controls DNA methylation patterns in Arabidopsis.

As obligate photosynthetic organisms plants are particularly exposed to the damaging effects of excess light and ultraviolet wavelengths, which can impact genome and epigenome dynamics by inducing DNA sequence and chromatin alterations. DNA DAMAGE-BINDING PROTEIN 2 (DDB2) is the main factor involved in the recognition of UV-induced DNA lesions during Global Genome Repair (GGR) in mammals and in plants. 1 In a recent study we reported that, in Arabidopsis, loss of DDB2 function alters DNA methylation patterns at many repeat loci and protein coding genes. We demonstrated that DDB2 acts in a complex with ARGONAUTE 4 (AGO4) to control de novo DNA methylation via the modulation of the local abundance of 24-nt small interfering RNAs (siRNAs). In addition, we found that DDB2 negatively regulates the expression of REPRESSOR OF SILENCING 1 (ROS1), a primary factor required for active DNA demethylation. Here we report that depletions of cognate GGR factors also lead to alterations of DNA methylation profiles at particular loci. Taken together, these findings reveal an interplay between GGR factors and DNA methylation patterns.