title: Dual role for 14-3-3 proteins and ABF transcription factors in gibberellic acid and abscisic acid signalling in barley (Hordeum vulgare) aleurone cells.
abstract: The balance of gibberellins [gibberellic acid (GA)] and abscisic acid (ABA) is a determining factor during transition of embryogenesis and seed germination. Recently, we showed that 14-3-3 proteins are important in ABA signalling in barley aleurone cells. Using 14-3-3 RNAi constructs in the barley aleurone transient expression system, we demonstrate here that silencing of each 14-3-3 isoform suppresses GA induction of the alpha-amylase gene. 14-3-3 Proteins interact with ABA-responsive element (ABRE) binding factors HvABF1, 2 and 3, and here we show that these transcription factors also interact with the ABA-responsive kinase PKABA1, a kinase that mediates cross-talk between the GA and ABA pathway. ABF1 and ABF2 have a function in both signalling pathways as: (1) ectopic expression of wild-type ABF1 and mutant ABF2, lacking the 14-3-3 interaction domain, transactivates the ABA inducible HVA1 gene; and (2) GA induction of the alpha-amylase gene is repressed by ectopic expression of wild-type ABF1 and 2. Mutant ABF1 and 2 were still effective repressors of GA signalling. In summary, our data provide evidence that 14-3-3 proteins and members of the ABF transcription factor family have a regulatory function in the GA pathway and suggest that PKABA1 and ABF transcription factors are cross-talk intermediates in ABA and GA signalling.
authors.affiliation: Vrije Universiteit Amsterdam, Faculty Earth and Life Sciences, Department of Structural Biology, De Boelelaan 1085, 1081 HV Amsterdam, the Netherlands.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Schoonheim
authors.forename: Daniel D A
authors.initials: DD
authors.lastname: Costa Pereira
authors.forename: Albertus H
authors.initials: AH
authors.lastname: De Boer
mesh_terms: D048948:14-3-3 Proteins / Q000235:genetics / Q000378:metabolism*; D000040:Abscisic Acid / Q000378:metabolism*; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D005875:Gibberellins / Q000378:metabolism*; D001467:Hordeum / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction; D000516:alpha-Amylases / Q000378:metabolism
chemical_list: D048948:14-3-3 Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D005875:Gibberellins; D010940:Plant Proteins; D020033:Protein Isoforms; D000040:Abscisic Acid; C007842:gibberellic acid; D011494:Protein Kinases; D000516:alpha-Amylases