GA suppresses the conversion from α-linolenic acid to JA through the GhGAI1-GhMYC3-GhLOX3 module to promote cotton fiber elongation

Cotton fibers are essential raw materials for the textile industry and serve as a classical model for studying cell elongation. During the elongation phase, cotton fibers accumulate significant amounts of linolenic acid, which is an essential component of cell membranes and a key precursor for jasmonic acid (JA) biosynthesis. Although JA is known to play a critical role in fiber development, the regulatory mechanisms governing the conversion of linolenic acid to JA remain largely unknown. Our study compared linolenic acid metabolism in elongating cotton fibers with that in roots and seed coats. We discovered that JA biosynthesis from linolenic acid is specifically suppressed in elongating fibers. We further identified gibberellin as a key regulator of linolenic acid metabolism through a DELLA protein-mediated pathway. Specifically, high levels of gibberellin in rapidly elongating fibers promote the degradation of the DELLA protein GhGAI1. This degradation facilitates the interaction between GhJAZ3 and GhMYC3, a transcriptional factor of the lipoxygenase gene, GhLOX3, ultimately inhibiting JA biosynthesis. Our findings illuminate how gibberellin precisely balances JA suppression with high linolenic acid accumulation to drive rapid fiber elongation, offering promising targets for enhancing cotton fiber quality.