The strigolactone-gibberellin crosstalk mediated by a distant silencer fine-tunes plant height in upland cotton.

The optimal plant height is crucial in modern agriculture, influencing lodging resistance and facilitating mechanized crop production. Upland cotton (Gossypium hirsutum) is the most crucial fiber crop globally, but the knowledge of the genetic basis underlying plant height still needs to be discovered. Here we conducted a genome-wide association study (GWAS) to identify the major locus controlling plant height (PH1) in upland cotton. The locus encodes gibberellin 2-oxidase 1A (GhPH1), with a 1,133 bp-length structural variation (PAV^PH1) located approximately 16 kb upstream of it. The presence or absence of PAV^PH1 confers a differential expression of GhPH1, consequently leading to changes in plant height. Further analysis revealed that a gibberellin-regulating transcription factor (GhGARF) recognizes a specific 'CATTTG' motif on the GhPH1 promoter and PAV^PH1. This binding event down-regulates GhPH1, indicating that PAV^PH1 functions as a distant upstream silencer. Intriguingly, we found that the critical repressor of the strigolactone (SL) signaling pathway, DWARF53 (D53), directly interacts with GhGARF and inhibits its binding to targets. Moreover, our study uncovers a previously unrecognized GA-SL crosstalk mechanism mediated by the GhD53-GhGARF-GhPH1/PAV^PH1 module, crucial in regulating the plant height of upland cotton. These findings shed light on the genetic basis and gene interaction network underlying plant height and provide valuable insights for developing semi-dwarf cotton varieties through precise modulation of GhPH1 expression.