Transcriptional and post-transcriptional regulatory networks controlling cotton fibre development.

Cotton fibre development is an extreme form of plant cell differentiation in which a single ovule epidermal cell undergoes fate specification, sustained polar elongation, secondary cell wall thickening, and terminal maturation. This review provides a stage-resolved synthesis of the transcriptional and post-transcriptional regulatory mechanisms that govern fibre development from initiation through maturation. We dissect the hierarchical organisation and functional interplay of major transcription factor families including MYB and MYBMIXTA-like proteins, HD-ZIP IV homeobox factors, WRKY, bHLH, NAC, TCP, bZIP, AP2/ERF, and zinc finger proteins and examine how these regulators coordinate epidermal cell fate acquisition, elongation-associated cell wall remodelling, and the onset of cellulose-dominated secondary wall biosynthesis. We further integrate evidence for post-transcriptional regulation mediated by microRNAs, phased siRNAs, and alternative splicing, highlighting their roles in shaping developmental timing, hormone-responsive transcriptional outputs, and regulatory stability across fibre developmental transitions. Genomic, epigenomic, transcriptomic, proteomic, and metabolomic studies are synthesised to illustrate how dynamic chromatin states, RNA processing, and metabolic reprogramming intersect with transcription factor networks in a stage-dependent manner. The review also examines how polyploidy, subgenome expression bias, and regulatory divergence among Gossypium species contribute to variation in fibre morphology and quality traits.