Seed germination and postgerminative growth are regulated by a delicate hormonal balance. @entity2271 (ABA) represses @entity958 seed germination and postgerminative growth, while @entity11406 ( @entity4375 ) antagonize ABA-mediated inhibition and promote these processes. However, the molecular mechanism underlying BR-repressed ABA signaling remains largely unknown. Here, we show that the Glycogen Synthase Kinase 3-like kinase BRASSINOSTEROID INSENSITIVE2 (BIN2), a critical repressor of BR signaling, positively regulates ABA responses during seed germination and postgerminative growth. Mechanistic investigation revealed that BIN2 physically interacts with ABSCISIC ACID INSENSITIVE5 (ABI5), a bZIP transcription factor. Further genetic analysis demonstrated that the ABA-hypersensitive phenotype of BIN2-overexpressing plants requires ABI5. BIN2 was found to phosphorylate and stabilize ABI5 in the presence of ABA, while application of epibrassinolide (the active form of @entity4375 ) inhibited the regulation of ABI5 by BIN2. Consistently, the ABA-induced accumulation of ABI5 was affected in BIN2-related mutants. Moreover, mutations of the BIN2 phosphorylation sites on ABI5 made the mutant protein respond to ABA improperly. Additionally, the expression of several ABI5 regulons was positively modulated by BIN2. These results provide evidence that BIN2 phosphorylates and stabilizes ABI5 to mediate ABA response during seed germination, while @entity4375 repress the BIN2-ABI5 cascade to antagonize @entity2272 -mediated inhibition.

BRASSINOSTEROID INSENSITIVE2 Interacts with ABSCISIC ACID INSENSITIVE5 to Mediate the Antagonism of @entity11406 to @entity2271 during Seed Germination in XXXX .

@entity2272 :: ('CHEBI:2365', 'Chemical') :: ['ABA'] @entity2271 :: ('MESH:D000040', 'Chemical') :: ['Abscisic acid'] @entity11406 :: ('MESH:D060406', 'Chemical') :: ['brassinosteroids'] @entity958 :: ('3702', 'Species') :: ['Arabidopsis thaliana'] @entity4375 :: ('11246', 'Species') :: ['BRs']
@entity958 :: (3702,Species) :: ['Arabidopsis']
