N6-methyladenosine RNA modification regulates photoperiod sensitivity in cotton.

The methylation of N6-methyladenosine (m6A) involves writers, erasers, and readers, acting synergistically in posttranscriptional regulation. These processes influence various biological processes, including plant floral transition. However, the specific role of m6A modifications in photoperiod sensitivity in cotton (Gossypium hirsutum) remains obscure. To elucidate this, in this study, we conducted transcriptome-wide m6A sequencing during critical flowering transition stages in the photoperiod-sensitive wild G. hirsutum var. yucatanense (yucatanense) and the photoperiod-insensitive cultivated cotton G. hirsutum acc. TM-1 (TM-1). Our results revealed significant variations in m6A methylation of 2 cotton varieties, with yucatanense exhibiting elevated m6A modification levels compared with TM-1 under long-day conditions. Notably, distinct m6A peaks between TM-1 and yucatanense correlated significantly with photoperiod sensitivity. Moreover, our study highlighted the role of the demethylase G. hirsutum ALKB homolog 5 (GhALKBH5) in modulating m6A modification levels. Silencing GhALKBH5 led to a decreased mRNA level of key photoperiodic flowering genes (GhADO3, GhAGL24, and GhFT1), resulting in delayed bud emergence and flowering. Reverse transcription quantitative PCR analyses confirmed that silencing GhADO3 and GhAGL24 significantly downregulated the expression of the floral integrator GhFT1. Collectively, our findings unveiled a transcriptional regulatory mechanism in which GhALKBH5-mediated m6A demethylation of crucial photoperiodic flowering transcripts modulated photoperiod sensitivity in cotton.