Auxin-mediated acceleration of flowering time via strengthening GhAUX22D-GhFT interaction in cotton

Flowering time, a core determinant of early-maturing in cotton, is regulated by an intricate network involving photoperiod, autonomous, vernalization, gibberellin, and temperature signaling pathways, with FLOWERING LOCUS T (FT) serving as a central floral integrator. GhFT, a homolog gene of FT, could accelerate flowering time in cotton, while the regulatory mechanisms of GhFT remain incompletely characterized. This study identified GhAUX22D as a novel GhFT-interacting protein through yeast two-hybrid (Y2H) screening, with interactions validated by LCA (Luciferase Complementation Assay) and BiFC (Bimolecular Fluorescence Complementation) assays. Spatiotemporal expression profiling and in situ hybridization revealed GhAUX22D's involvement in cotton maturation processes. Functional validation using VIGS-suppressed cotton and transgenic Arabidopsis demonstrated GhAUX22D's positive role in flowering time. Crucially, auxin signaling was found to enhance GhFT-GhAUX22D interaction, suggesting a phytohormonal regulatory layer in flowering control. This study advances our understanding of flowering time mechanisms in cotton and contributes to the cultivation and breeding of early-maturing cotton cultivars.