Genome-wide identification and comparative analysis of DNA methyltransferase and demethylase gene families in two ploidy Cyclocarya paliurus and their potential function in heterodichogamy

BACKGROUND: DNA methylation is one of the most abundant epigenetic modifications, which plays important roles in flower development, sex differentiation, and regulation of flowering time. Its pattern is affected by cytosine-5 DNA methyltransferase (C5-MTase) and DNA demethylase (dMTase). At present, there are no reports on C5-MTase and dMTase genes in heterodichogamous Cyclocarya paliurus. RESULTS: In this study, 6 CpC5-MTase and 3 CpdMTase genes were identified in diploid (2n = 2 × = 32) C. paliurus, while 20 CpC5-MTase and 13 CpdMTase genes were identified in autotetraploid (2n = 4 × = 64). 80% of identified genes maintained relatively fixed positions on chromosomes during polyploidization. In addition, we found that some DRM subfamily members didn’t contain the UBA domain. The transcript abundance of CpC5-MTase and CpdMTase in male and female flowers of two morphs (protandry and protogyny) from diploidy was analyzed. Results showed that all genes were significantly up-regulated at the stage of floral bud break (S2), but significantly down-regulated at the stage of flower maturation (S4). At S2, some CpC5-MTase genes showed higher expression levels in PG-M than in PG-F, whereas some CpdMTase genes showed higher expression levels in PA-M than in PA-F. In addition, these genes were significantly associated with gibberellin synthesis-related genes (e.g. DELLA and GID1), suggesting that DNA methylation may play a role in the asynchronous floral development process through gibberellin signal. CONCLUSIONS: These results broaden our understanding of the CpC5-MTase and CpdMTase genes in diploid and autotetraploid C. paliurus, and provide a novel insight into regulatory mechanisms of DNA methylation in heterodichogamy. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12864-023-09383-5.