Histone H3 lysine 27 trimethylation (H3K27me3) modulates the fiber cell initiation in upland cotton

Histone methylation is pivotal in regulating the expression of numerous essential functional genes in plants. However, its specific function and mechanism in cotton fiber cell initiation remain poorly understood. The upland cotton ( Gossypium hirsutum L.) variety Xuzhou142 (Xu142) and its fuzzless-lintless mutant Xu142 fl are ideal model materials for studying cotton fiber cell development. In vitro ovule culture analysis showed that the histone H3 lysine 27 trimethylation (H3K27me3) inhibitor RDS 3434 could inhibit fiber cell initiation and development. Cleavage under targets and tagmentation (CUT&Tag) and RNA sequencing (RNA-seq) data of −1, 0, and 1 day post-anthesis (DPA) ovules showed that H3K27me3 regulates fiber cell initiation by highly accumulating in Xu142 than in Xu142 fl . It was also found that H3K27me3 was negatively correlated with gene transcription, as 227 expressed genes showed an opposite trend to the H3K27me3 modification level and were identified to participate in multiple signaling pathways. Furthermore, the expression levels of ten potential genes related to fiber development were confirmed to correlate with H3K27me3 levels. The results demonstrate the critical role of H3K27me3 in fiber development process and present evidence supporting its involvement in cotton fiber cell initiation. The study lays the foundation and provides genetic resources for further investigations into genes related to fiber development. • RDS 3434 inhibits cotton fiber cell initiation and development via H3K27me3 suppression. • H3K27me3 accumulates more in Xu142 than in Xu142 fl , indicating its regulatory role. • H3K27me3 levels negatively correlate with gene transcription in cotton ovules. • 227 genes were identified with expression patterns opposite to H3K27me3 modification.