The transcription factor GmFULc regulates soybean plant height by binding the promoter of a gibberellin-responsive gene

Plant height is a crucial agronomic characteristic that substantially influences soybean [Glycine max (L.) Merr.] yield. FRUITFULLc (GmFULc) is a MADS-box transcription factor that acts as a growth promoter in soybean; however, the mechanism by which GmFULc regulates soybean height is unknown. This study revealed that GmFULc:GmFULc (the expression of the GmFULc gene driven by its native promoter) soybeans exhibit increased plant height and longer internodes. Conversely, soybean plants containing fulc mutations showed reduced plant height and shortened internodes. Chromatin immunoprecipitation-qPCR revealed GmFULc promotes the expression of gibberellic acid-stimulated Arabidopsis 14 (GmGASA14) and GmGASA32 by directly binding to G-boxes in their promoter regions, leading to notably increased expression of GmGASA14 and GmGASA32 in GmFULc:GmFULc soybean plants and reduced expression in soybean plants containing the fulc-2 mutation. The GmFULc-mediated enhanced expression of GmGASA14 and GmGASA32 increased the gibberellin signal, which may have inhibited gibberellin synthesis by increasing gibberellin 2-oxidase (GmGA2ox) expression and decreasing GA20ox expression. Our findings suggest that GmFULc promoted the expression of GmGASA genes by directly binding to G-boxes in their promoters to regulate soybean plant height.