Studies on DEMETERs Promoter and N-terminal Domain Function in Arabidopsis thaliana

Abstract

The development of the female gametophyte in plants is tightly regulated by epigenetic mechanisms to ensure the proper development of seeds. DNA methylation is an evolutionarily conserved mechanism that controls numerous biological processes such as gene imprinting, gene expression, and paramutation. In plants, DNA methylation occurs in the CG, CHG, and CHH contexts. The regulation of DNA methylation is done by a family of DNA demethylase genes including DEMETER (DME), REPRESSOR OF SILENCING 1 (ROS1), DEMETER LIKE 2 (DML2), and DEMETER LIKE 3 (DML3). Both DME and ROS1 are bifunctional DNA glycosylases that initiate active DNA demethylation through the base excision repair pathway. dme mutant plants exhibit severe seed abortion phenotypes as maternally expressed genes including MEDEA (MEA) cannot be activated. The structure of DME includes two splice variants, Spain and Berkeley DME with Spain being 258 amino acids longer on the N-terminal side. DME can further be split up into the N-terminal Domain and the C-terminal domain consisting of the A, G and B domains. Currently, the function of the N-terminal domain is unclear as the C-terminal side was shown to have glycosylase functions in vitro. Dominant negative strategies were done to provide a possible explanation to the function of the N-terminal domain. Transcriptional controls of DME show unexpected expression patterns opening the possibility that another factor controls DME expression. A series of differential DME fragments also showed unexpected GFP expression patterns.