Epigenetic controls of plant development and genome structure

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FWA has been identified as the gene responsible for a late-flowering epigenetic trait (Mol Cell 6, 791-). In this project, we examined expression of the FWA gene during normal development. The FWA gene was expressed specifically in endosperm in an imprinted manner. The tissue-specific and imprinted FWA expression depends on DNA methyltransferase MET1 and DNA demethylase DEMETER (Science 303, 521-). It was also shown that FT is the inducer of flowering (Science 309, 1052-), and the FWA affects flowering by inhibiting the FT function at the protein level (Plant Cell Physiol 48, 205-).We have previously shown that Arabidopsis CACTA transposons are silent in wild type, but they are mobilized in mutant of a chromatin remodeling gene DDM1 (decrease in DNA methylation) (Nature 411, 212-). In this project, we showed that the CACTA transposons transposed in the double mutants of CG methylase MET1 and non-CG methylase CMT3. The results suggest that DNA methylation is necessary for immobilization of this class of transposons (Curr Biol 13, 421-).Transcription of CACTA was de-repressed by mutations in the MET1 or a chromatin assembly factor FAS (Curr Biol 13, 421-, Genes to Cells 18, 153-). Heterochromatin in CACTA locus or other peri-centromeric sequences was disrupted by the ddml mutation, and this effect was heritable even in the wild type background (EMBO J 21, 6549-). Using this system, we also showed that each of CACTA transposition was not targeted to heterochromatin (Genetics 168, 961-). It is interesting how the transposons accumulate to form the heterochromatin.