• Exogenous application of 50 µmol/L ABA significantly enhanced flavonoid accumulation in A. manihot . • Confirmed that AmCHI is a key gene for flavonoid synthesis in A. manihot , and AmABI5 binds to the ABRE element in the AmCHI promoter to inhibit its transcription. • Revealed a unique flavonoid-mediated ABA response mechanism in A. manihot , which operates via the CHI-ABI5 module. Flavonoids are important secondary metabolites in plants, playing crucial roles in plant growth, development, and stress resistance. Abelmoschus manihot L. is an economic crop that exhibits distinct organ-specific flavonoid accumulation with flowers and leaves as the main flavonoid-storing organs. These organs serve as core resources for the natural medicine and functional food industries. However, flavonoid content in these key organs shows significant geographical and batch-related instability, which has emerged as a critical bottleneck constraining industrial development. Abscisic acid (ABA) has been reported to enhance flavonoid accumulation in plants. Currently, research on the flavonoid metabolic pathway of A. manihot remains limited, and the regulatory role of ABA in this pathway is still unclear. Our study demonstrated that exogenous ABA application significantly enhanced flavonoid accumulation in A. manihot , and 50 μmol/L was identified as the optimal concentration. Through experiments including yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA), and chromatin immunoprecipitation (ChIP), the core mechanism was identified, the transcription factor AmABI5 induced by ABA can directly bind to the ABRE cis-acting element in the promoter region of the AmCHI gene, represses the transcriptional activity of this gene, form a negative feedback regulatory loop, and ultimately lead to increased flavonoid content. These results not only deepen our understanding of the flavonoid metabolic regulatory network in A. manihot but also provide key targets and a theoretical basis for molecular breeding or agronomic practices aimed at resolving flavonoid content instability and improving flavonoid yield.
Chu et al. (Sun,) studied this question.