GhPIF4–GhEXL2 module mediates floral transition promotion in cotton (Gossypium hirsutum L.)

The timing of floral transition represents a pivotal agronomic trait that governs precocity in cultivated cotton ( Gossypium hirsutum L.). Despite the established involvement of the EXO/EXL and PIF families in plant growth and development, little is known about their collaborative functions in flowering regulation, especially in cotton. Through EMSA, yeast one-hybrid assays, and dual-luciferase reporter experiments, GhPIF4 was confirmed to physically associate with the GhEXL2 promoter and stimulate its transcriptional activity. The involvement of these two genes in flowering time regulation was further examined via gain-of-function analysis in Arabidopsis and loss-of-function analysis in cotton using virus-induced gene silencing. Overexpression of either GhEXL2 or GhPIF4 in Arabidopsis significantly accelerated flowering, whereas silencing of either gene in cotton delayed flowering. Notably, exogenous auxin treatment induced synchronized upregulation of both genes. Collectively, these findings establish the GhPIF4 – GhEXL2 module as a novel auxin-responsive node governing flowering time in cotton, thereby expanding the functional repertoire of both gene families and providing a promising target for molecular breeding of early-maturing varieties.