DNA methylation is an important epigenetic mechanism that regulates a wide range of biological processes in plants, including growth, development, secondary metabolism, and stress responses. This dynamic modification is regulated by cytosine-5 DNA methyltransferases (C5-MTases) and DNA demethylases (dMTases). There has been extensive research on DNA methylation in plants. Despite this, chrysanthemums are still underexplored, despite possessing diverse varieties, a large genome, and a complex evolutionary history. In this study, a total of 69 C5-MTase genes and 24 dMTase genes were identified across four chrysanthemum species. Phylogenetic analysis classified these genes into four subfamilies of C5-MTase and three subfamilies of dMTase. Among the chrysanthemum species analyzed, these genes are distributed across 7–19 chromosomes, with segmental duplication being the main factor behind their family expansion. Expression profiling demonstrated unique spatiotemporal expression patterns for all C5-MTase and dMTase genes in varied tissues, along with their varying responses to abiotic stresses such as salt and drought. Functional characterization indicated that Arabidopsis plants overexpressing ClMET1a showed a notably reduced germination rate compared to wild-type (WT) after 24 h under 150 mM salt stress. RNA-seq analysis pinpointed the nitrate transporter gene AtNRT2.6 , whose promoter’s methylation level was significantly heightened in the overexpressing lines. This finding indicates that ClMET1a may modulate methylation of the AtNRT2.6 promoter, thereby influencing germination rates in Arabidopsis under salt stress. In summary, this study provides valuable insights into the functions of C5-MTase and dMTase gene families in chrysanthemum, particularly in plant development and stress adaptation. • 69 C5-MTases and 24 dMTases were identified in four chrysanthemum species . • ClC5-MTases and CldMTases exhibit tissue-specific and stress-induced expression. • ClMET1a overexpression delays Arabidopsis germination under salt stress. • ClMET1a could increase the methylation levels of AtNRT2.6 promoter.
Shi et al. (Sat,) studied this question.