GhMYB2-activated GhADC2 interacts with GhBCCP1 to regulate cotton fiber development

Arginine decarboxylase (ADC), a rate-limiting enzyme in the polyamine biosynthesis pathway, plays a critical role in plant growth and development. Our previous study revealed that cotton GhADC2 has potential to regulate fiber initiation. In this study, we further elucidate the molecular mechanism by which GhADC2 regulates fiber development. Overexpression of GhADC2 significantly enhanced fiber elongation, whereas RNAi-mediated suppression of GhADC2 resulted in shorter fibers. Further analysis demonstrated that the promoter of GhADC2 is transcriptionally regulated by transcription factor GhMYB2. Subcellular localization assays using Arabidopsis protoplasts and tobacco leaves revealed that GhADC2 localizes to the cell nucleus, differing from the usual chloroplast localization of ADCs. Yeast library screening identified GhBCCP1, a nuclear-targeted protein in cotton fibers, as an interacting partner of GhADC2. GhBCCP1 directly regulates plant physiological processes by catalyzing the conversion of acetyl-CoA to malonyl-CoA. Metabolomic sequencing of GhADC2 overexpression and RNAi plants highlighted significant enrichment in the tryptophan metabolism and flavonoid biosynthesis pathways. Collectively, our data demonstrate that GhADC2 is a positive regulator of cotton fiber development, and that it is transcriptionally activated by GhMYB2 and physically interacts with GhBCCP1, suggesting that these three components form a regulatory module associated with fiber growth. These findings provide valuable information for improving cotton fiber quality.