Distinct DNA methylomes of moso bamboo in the phase transition from vegetative to reproductive growth

In mammals, it is well known that DNA methylation has important roles during aging. However, age-related DNA methylation changes during phase transitions largely remain unclear in plants. Moso bamboo needs a very long time to transition from vegetative to floral phase. To comprehensively investigate the influence of DNA methylation on aging, we present here a distinctive single-base-resolution DNA methylation profile using both high-throughput bisulfite sequencing (BS-Seq) and single-molecule nanopore-based DNA sequencing, which covers the long period of vegetative growth and transition to flowering of moso bamboo’s development. We discovered that CHH methylation gradually accumulated from vegetative to reproductive growth in a time-dependent fashion. Importantly, DMR (differential DNA methylation) correlating with chronological aging occurred preferentially at both transcription start sites (TSS) and transcription termination sites (TTS). Genes with CG methylation changes showed enrichment of gene ontology (GO) categories in ‘vegetative to reproductive phase transition of meristem’. In addition, In combination with mRNA sequencing (RNA-Seq) revealed that DNA methylation in promoter, intron, and exon has different roles in regulating gene expression. Finally, circular RNA sequencing (circRNA-Seq) revealed that flanking introns of circRNAs show hypermethylation. Further analysis revealed that these flanking introns were enriched in LTR-retrotransponsons. Together, observations in this study provide insights about dynamic DNA methylation and circRNAs landscape with chronological ages, which paves the way to further study the impact of epigenetic factors on flowering in moso bamboo. In this study we used Oxford Nanopore Technologies (ONT) to directly identify 5mC by detection of electrical current signals for three week leaf and flower leaf, respectively.