Arabidopsis thaliana

DNA methylation is an important epigenetic modification involved in many biologcial processes, and active DNA demethylation plays critical roles in regulating expression of genes and anti-silencing of transgenes. In this study, we isolated mutations in one arabidopsis gene, ROS5, which causes the silencing of transgenic 35S-NPTII because of DNA hypermethylation, but no effect on transgenic RD29A-LUC. ROS5 encodes an atypical small heat shock protein. ROS5 can physically interact with IDM1 and is required for preventing DNA hypermethylation of some endogenous genes that are also regualated by IDM1 and ROS1. We propose that ROS5 may regulate active DNA demethylation by interacting with IDM1, thereby creating a friendly chromatin environment that facilitates the binding of ROS1 to erase DNA methylation.