DNA methylation/ demethylation plays essential roles in the control of gene expression and genome integrity. Although recent studies have identified some DNA demethylation enzymes in plants and animals, it is clear that many other factors controlling this process still remain to be discovered.

Assistant professor Yoko Ikeda, Associate professor Tetsu Kinoshita and coworkers in the laboratory of Plant Reproductive Genetics, Graduate School of Biological Sciences, have found that SSRP1 (sturucture specific recognition protein 1), a component of FACT histone chaprone, is required for DNA demethylation and genomic imprinting in Arabidopsis thaliana. The group identified mutant plants that were defective in activation of a gene (FWA) that is known to be imprinted. In wild type plants, the maternally inherited copy of FWA is expressed in the endosperm after fertilization, while the paternally inherited copy is silent. By contrast, in the mutant plants, expression of the maternal FWA fails because of a defect in demethylation of specific region of the gene (the 5' SINE-related repeat). This failure in demethylation was due to mutation of the gene encoding SSRP1. Based on the genetic analyses using met1 (methyltransferase 1), dme-1 (DNA demethylase) and ssrp1 mutants, the group has proposed a model for a chromatin-based mechanism that controls DNA demethylation in plants.

【Related link】
The paper is published in the Journal below.
http://dx.doi.org/10.1016/j.devcel.2011.08.013
http://library.naist.jp/dspace/handle/10061/6337（NAIST Academic Repository: naistar）

Here is the bibliographic information of the paper.
Ikeda, Yoko; Kinoshita, Yuki; Susaki, Daichi; Ikeda, Yuriko; Iwano, Megumi; Takayama, Seiji; Higashiyama, Tetsuya; Kakutani, Tetsuji; Kinoshita, Tetsu. HMG Domain Containing SSRP1 Is Required for DNA emethylation and Genomic Imprinting in Arabidopsis. DEVELOPMENTAL CELL. 12 September 2011

Here is the bibliographic information of the paper
Yoko Ikeda, Yuki Kinoshita, Daichi Susaki,Yuriko Ikeda, Megumi Iwano, Seiji Takayama, Tetsuya Higashiyama, Tetsuji Kakutani, Tetsu Kinoshita. HMG domain containing SSRP1 is required for DNA demethylation and genomic imprinting in Arabidopsis. Developmental Cell (2011) Sep 13, 21(3):589-96.