Extensive reprogramming of cytosine methylation in Oryza allotetraploids

Cytosine methylation is a prominent epigenetic modification in plants and it has been proposed to as causative for silencing some duplicates derived by polyploidization. Several synthetic polyploids have shown there is a dynamic epigenetic change following hybridization and genome doubling. Relatively few studies, however, have focused on wild natural polyploids. In this study, using a methylation-sensitive amplified fragment length polymorphism method, we investigated the levels and types of cytosine methylation in three Oryza CCDD genome allotetraploids and their related diploids with CC and EE genomes. We show an overall minor increase in methylation level in the allopolyploids, but extensive methylation reprogramming (70 %), with almost equivalently increased (22-26 %) and decreased methylation (25-27 %). Our study reveals a complicated epigenetic change in natural polyploids. The information presented in the study will be of some utility to molecular taxonomists and also rice breeders working on wide-hybridization