Abscisic Acid Modulates Seed Germination via ABA INSENSITIVE5-Mediated PHOSPHATE1.

The phytohormone abscisic acid (ABA) controls many developmental and physiological processes. Here, we report that PHOSPHATE1 (PHO1) participates in ABA-mediated seed germination and early seedling development. The transcription of was obviously enhanced during seed germination and early seedling development and repressed by exogenous ABA. The mutants (, , and ) showed ABA-hypersensitive phenotypes, whereas the -overexpressing lines were ABA-insensitive during seed germination and early seedling development. The expression of was repressed in the -overexpressing line and elevated in the mutant, and ABI5 can bind to the promoter in vitro and in vivo, indicating that ABI5 directly down-regulated expression. Disruption of abolished the ABA-insensitive germination phenotypes of mutant, demonstrating that was epistatic to Together, these data demonstrate that PHO1 is involved in ABA-mediated seed germination and early seedling development and transcriptionally regulated by ABI5.