GhMYB102 affects cotton fibre elongation and secondary wall thickening by regulating GhIRX10 in cotton

Summary Upland cotton ( Gossypium hirsutum ) is a principal economic crop and a fundamental raw material for the textile industry. The quality of cotton fibres is significantly influenced by the synthesis of cell wall polysaccharides. This study focuses on GhIRX10 , a beta‐1,4‐xylosyltransferase crucial for xylan backbone synthesis. Overexpression of GhIRX10 enhances xylan synthesis, which impacts fibre elongation and secondary cell wall thickening. GhMYB102 , identified as a direct regulator of GhIRX10 expression, was confirmed through comprehensive validation. Overexpression of GhMYB102 resulted in a similar phenotype as OE‐ GhIRX10 : increased cell wall thickness and reduced fibre length. Overexpression of GhMYB102 upregulated the expression of key cell wall synthesis‐related genes, including GhCESA4/7/8 , Gh IRXs , GhCESAs , Gh GUXs , Gh TBLs , Gh XTHs , and Gh XXTs . Consequently, the cellulose and hemicellulose contents in OE‐ GhMYB102 lines were significantly increased. GhMYB102 was also validated as a target gene regulated by GhFSN1 and GhMYB7 , with the ability to reciprocally regulate GhFSN1 expression. In summary, we propose a regulatory model where GhMYB102 promotes the expression of GhIRX10 and other cell wall‐related genes, thereby affecting fibre quality. This study elucidates the regulatory network of secondary cell wall synthesis in cotton and provides potential targets for improving fibre quality through molecular breeding.