DNA hypomethylation mediates flower opening and senescence in sweet osmanthus through auxin and ethylene responsive pathways.

Recent studies have shown that DNA methylation is critical for fruit ripening and leaf senescence, but its effect on flowering is unclear. This study investigated the dynamic changes in DNA methylation and its regulatory role on flower opening and senescence of Osmanthus fragrans "Liuyejingui" by whole-genome bisulfite sequencing and transcriptome sequencing at six developmental stages (unopened floral bud to late flower senescence, S1 to S6). In total 3222 differentially methylated regions (DMRs) were identified in senescent flowers, of which 89% were hypomethylated (hypo-DMRs), and the number increased form S1 to S6, suggesting that DNA demethylation is associated with the progression of flowering. Analysis of hypo-DMR-associated up-regulated differentially expressed genes revealed that small auxin up-regulated RNAs (OfSAURs) were the most highly significantly enriched from S3 to S5, and ethylene-responsive transcription factors (OfERFs) were strongly activated in senescent flowers. These results suggested that DNA hypomethylation was important for...