Genome-Wide Identification of DNA Methylases and Demethylases in Kiwifruit (Actinidia chinensis)

DNA methylation plays an important role in a wide range of developmental and physiological processes in plants. It is primarily catalyzed and regulated by cytosine-5 DNA methyltransferases (C5-MTases) and a group of DNA glycosylases that act as demethylases. To date, no genome-scale analysis of the two kiwifruit (Actinidia chinensis) families has been undertaken. In our study, nine C5-MTases and seven DNA demethylase genes were identified in the kiwifruit genome. Through selective evolution analysis, we found that there were gene duplications in C5-MTases and demethylases, which may have arisen during three genome doubling events followed by selection during evolution of kiwifruit. Expression analysis of DNA methylases (C5-MTases) and demethylases identified changes in transcripts of DNA methylation and demethylation genes during both vegetative and reproductive development. Moreover, we found that some members of the two methylase/demethylase families may also be involved in fruit ripening and the regulation of softening. Our results help to better understand the complex roles of methylation/demethylation in plants and provide a foundation for analyzing the role of DNA methylation modification in kiwifruit growth, development and ripening.