FIERY1 encoding an inositol polyphosphate 1-phosphatase is a negative regulator of abscisic acid and stress signaling in Arabidopsis

The plant hormone abscisic acid (ABA) plays a wide range of important roles in plant. growth and development, including embryogenesis, seed dormancy, root and shoot growth, transpiration, and stress tolerance. ABA and various abiotic stresses also activate the expression of numerous plant genes thro ugh undefined signaling pathways. To gain insight into ABA and stress signa l transduction, we conducted a genetic screen based on ABA- and stress -ind ucible gene transcription. Here we report the identification of an Arabidop sis mutation, fiery1 (fry1), which results in super-induction of ABA- and s tress-responsive genes. Seed germination and postembryonic development of f ry1 are more sensitive to ABA or stress inhibition. The mutant plants are a lso compromised in tolerance to freezing, drought, and salt stresses. Map-b ased cloning revealed that FRY1 encodes an inositol polyphosphate 1-phospha tase, which functions in the catabolism of inositol 1, 4, 5-trisphosphate ( IP3). Upon ABA treatment, fry1 mutant plants accumulated more IP3 than did the wild-type plants. These results provide the first genetic evidence indi cating that phosphoinositols mediate ABA and stress signal transduction in plants and their turnover is critical for attenuating ABA and stress signal ing.