Tuber mustard BjuFIP gene negatively regulates plant sensitivity to abscisic acid

Tuber mustard (Brassica juncea var. tumida) is an economically important vegetable crop, with its tumorous stem serving as the primary raw material for Fuling mustard production. However, multiple abiotic stress during growth often leads to significant yield losses. As a vital hormone for plant stress adaptation, abscisic acid (ABA) plays essential roles in stress responses. However, despite the agricultural importance of tuber mustard, no studies have yet reported on ABA related functions in this crop. In this study, we identified the F-box protein gene BjuFIP as a key regulator in ABA signaling. BjuFIP was ubiquitously expressed across all tissues and significantly upregulated by ABA treatment. Histochemical analysis of Pro_BjuFIP::GUS transgenic Arabidopsis seedlings further confirmed ABA-induced BjuFIP expression. Functional characterization revealed that Arabidopsis overexpressing BjuFIP exhibited an ABA-insensitive phenotype, suggesting that BjuFIP negatively regulates ABA signaling in tuber mustard. Furthermore, protein-protein interaction assays, including yeast two-hybrid and bimolecular fluorescence complementation, demonstrated that BjuFIP physically interacts with BjuASK1, a core component of the SCF ubiquitin ligase complex, and BjuPYL3, an ABA receptor. These findings suggest that BjuFIP might modulate the ABA signaling pathway through regulation of BjuPYL3. These findings not only advance our understanding of ABA signaling in tuber mustard but also offer valuable genetic targets for breeding stress-tolerant varieties with stable yields.