ABA functions in low phosphate-induced anthocyanin accumulation through the transcription factor ABI5 in Arabidopsis

Key message ABI5 functions in ABA-mediated anthocyanin accumulation in plant response to low phosphate. Abstract Low phosphate (LP)-induced anthocyanin biosynthesis and accumulation play an important role in plant adaptive response to phosphate starvation conditions. However, whether and how the stress phytohormone abscisic acid (ABA) participates in LP-induced anthocyanin accumulation remain elusive. Here, we report that ABA is required for LP-induced anthocyanin accumulation in Arabidopsis thaliana . Disrupting ABA DEFICIENT2 ( ABA2 ), a key ABA-biosynthetic gene, or BETA-GLUCOSIDASE1 ( BG1 ), a major gene implicated in converting conjugated ABA to active ABA, significantly impairs LP-induced anthocyanin accumulation, as LP-induced expression of the anthocyanin-biosynthetic genes Chalcone Synthase ( CHS ) is dampened in the aba2 and bg1 mutant. In addition, LP-induced anthocyanin accumulation is defective in the mutants of ABA signaling pathway, including ABA receptors, ABA Insensitive2, and the transcription factors ABA Insensitive5 (ABI5), suggesting a role of ABI5 in ABA-mediated upregulation of anthocyanin-biosynthetic genes in plant response to LP. Indeed, LP-induced expression of CHS is repressed in the abi5-7 mutant but further promoted in the ABI5 -overexpressing plants compared to the wild-type. Moreover, ABI5 can bind to and transcriptionally activate CHS , and the defectiveness of LP-induced anthocyanin accumulation in abi5-7 can be restored by overexpressing CHS . Collectively, our findings illustrates that ABI5 functions in ABA-mediated LP-induced anthocyanin accumulation in Arabidopsis.