MYB100-GA20ox3 Module Promotes Flowering by Activating Gibberellin Pathway in Brassica napus

Brassica napus (rapeseed) is the world's most important oilseed crop, and its flowering time is a key determinant of regional adaptation and yield optimization. Nevertheless, the molecular links between specific MYB transcription factors, gibberellin (GA) biosynthesis, and flowering control in rapeseed have not been fully deciphered. Here, we identify BnaC04.MYB100 as a novel positive regulator of flowering time. Overexpression of BnaC04.MYB100 accelerated flowering, whereas CRISPR/Cas9-mediated knockout (bnac04.myb100) delayed it. Transcriptome and hormone analyses reveal that BnaC04.MYB100 activates key flowering-network genes and the GA biosynthesis pathway, elevating endogenous GA levels. The late-flowering phenotype of the Arabidopsis atmyb100 mutant is rescued by exogenous GA. Using dual-luciferase reporter, yeast one-hybrid, ChIP-qPCR, and EMSA assays, we demonstrate that BnaC04.MYB100 directly binds to the AACTACT motif in the promoter of BnaGA20ox3, a rate-limiting GA biosynthetic gene. Natural variation in the BnaC04.MYB100 locus is strongly associated with flowering time diversity in a rapeseed natural germplasm panel and shows evidence of artificial selection during modern breeding. Our findings establish BnaC04.MYB100 as a central integrator linking GA biosynthesis to flowering time, providing a valuable genetic target for optimizing reproductive development and yield potential in rapeseed breeding.