Seed oil co ntent （SOC� and fatty acid （FA� composition determine the quality and eco nomic value of rapeseed （Brassica napus）� Little is known a bout the role of gibberellic acid （GA� in regulating FA biosynthesis in B. napus. Here, we discovered that four BnaRGAs （B. napus REPRESSOR OF GA）， encoding negative regulators of GA signalling, were suppressed during seed development. Compared to the wild type, SOC was reduced in gain‐of‐function mutants bnaa6.rga‐D and ds�?, which also showed reduced oleic acid and increased linoleic acid contents. By contrast, the loss‐of‐function quadruple mutant bnarga displayed higher SOC during early seed development than the wild type, with increased oleic acid and reduced linoleic acid contents. Notably, o nly BnaA6.RGA and BnaC7.RGA physically interacted with two BnaLEC1s, which function as essential trans cription factors in FA biosynthesis. The FA composition did not significantly differ between bnarga bnalec1 sextuple mutants and bnalec1, suggesting that BnaLEC1s are epistatic to BnaRGAs in the regulation of FA composition. Furthermore, BnaLEC1‐induced activation of BnaABI3 ex pression was repressed by BnaA6.RGA, indicating that GA triggers the degradation of BnaRGAs to relieve their repression of BnaLEC1s, thus promoting the trans cription of downstream genes to facilitate oil biosynthesis. Therefore, we uncovered a developmental stage‐specific role of GA in regulating oil biosynthesis via the GA‐BnaRGA‐BnaLEC1 signalling cascade, providing a novel mechanistic understanding of how phytohormo nes regulate FA biosynthesis in seeds. BnaRGAs represent promising targets for oil crop improvement.

　　论文链接：https://onlinelibrary.wiley.com/doi/abs/10.1111/pbi.13628