Abstract
The phytohormone abscisic acid (ABA) regulates plant growth, development and responses to biotic and abiotic stresses. The core ABA signaling pathway consists of three major components: ABA receptor (PYR1/PYLs), type 2C Protein Phosphatase (PP2C) and SNF1-related protein kinase 2 (SnRK2). Nevertheless, the complexity of ABA signaling remains to be explored. To uncover new components of ABA signal transduction pathways, we performed a yeast two-hybrid screen for SnRK2-interacting proteins. We found that Type One Protein Phosphatase 1 (TOPP1) and its regulatory protein, At Inhibitor-2 (AtI-2), physically interact with SnRK2s and also with PYLs. TOPP1 inhibited the kinase activity of SnRK2.6, and this inhibition could be enhanced by AtI-2. Transactivation assays showed that TOPP1 and AtI-2 negatively regulated the SnRK2.2/3/6-mediated activation of the ABA responsive reporter gene RD29B, supporting a negative role of TOPP1 and AtI-2 in ABA signaling. Consistent with these findings, topp1 and ati-2 mutant plants displayed hypersensitivities to ABA and salt treatments, and transcriptome analysis of TOPP1 and AtI-2 knockout plants revealed an increased expression of multiple ABA-responsive genes in the mutants. Taken together, our results uncover TOPP1 and AtI-2 as negative regulators of ABA signaling.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Abscisic Acid / genetics
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Abscisic Acid / metabolism*
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Arabidopsis / genetics*
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Arabidopsis / growth & development
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Arabidopsis Proteins / genetics*
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Arabidopsis Proteins / metabolism
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Cold Shock Proteins and Peptides / genetics
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Cold Shock Proteins and Peptides / metabolism
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Gene Expression Regulation, Plant
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Membrane Transport Proteins / genetics
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Membrane Transport Proteins / metabolism
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Phosphoprotein Phosphatases / genetics*
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Phosphoprotein Phosphatases / metabolism
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Plant Roots / genetics
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Plant Roots / growth & development
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Plants, Genetically Modified / genetics
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Plants, Genetically Modified / growth & development
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Protein Kinases / genetics
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Protein Kinases / metabolism
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Protein Phosphatase 1 / biosynthesis
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Protein Phosphatase 1 / genetics*
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Protein Phosphatase 1 / metabolism
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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Seedlings / genetics
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Seedlings / growth & development
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Signal Transduction
Substances
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Arabidopsis Proteins
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Cold Shock Proteins and Peptides
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Membrane Transport Proteins
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Pyr1 protein, Arabidopsis
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RD29B protein, Arabidopsis
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SnRK2 protein, Arabidopsis
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Abscisic Acid
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Protein Kinases
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OST1 protein, Arabidopsis
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SNF1-related protein kinases
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Protein Serine-Threonine Kinases
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AHG3 protein, Arabidopsis
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AtI-2 protein, Arabidopsis
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Phosphoprotein Phosphatases
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Protein Phosphatase 1
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TOPP1 protein, Arabidopsis