Sequence and Gene Expression Analysis of DNA Methyltransferase in Castor Bean (Ricinus communis L.)

DNA methylation, which can protect plant genome from adversity stress and regulate gene expression, is one of epigenetic modification. DNA methyltransferase is key enzyme for maintaining DNA methylation and de novo methylation. In this research, 8 putative genes encoding DNA methyltransferase were identified and characterized from castor bean (Ricinus communis) genome. These genes have been classified into MET, CMT, DRM and DNMT2 subfamilies based on phylogenetic relationship and domain organization, and their structures, conserved domains, and subcellular locations were also characterized. In addition, the gene expression was inspected through the high-throughput transcriptional sequencing data and RT-PCR methods. Results showed these proteins encoded by 8 genes were located at nucleus, and catalytic C-terminal domain with 6 conserved motifs have common methylation function, while the N-terminal domain of these proteins showed diverse structural features between different subfamilies, meanwhile, the lacking N-terminal domain presented in the RcDNMT2. Phylogenetically, the MET, CMT, DRM and DNMT2 were conservative and differentiated after mono- and dicot-cotyledon. The expression level of all genes in developing endosperm was higher than other detective tissues except RcDRM2, and hypothesized that endosperm hypomethylation can induce the high expression of these DNA methyltransferase genes during this period. These results contribute to understanding castor bean DNA methyltransferase comprehensively and provide a guidline for epigenetics breeding.