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Abscisic acid‐activated SNRK2 protein kinases function in the gene‐regulation pathway of ABA signal transduction by phosphorylating ABA response element‐binding factors

Abscisic acid‐activated SNRK2 protein kinases function in the gene‐regulation pathway of ABA... The plant hormone abscisic acid (ABA) induces gene expression via the ABA‐response element (ABRE) present in the promoters of ABA‐regulated genes. A group of bZIP proteins have been identified as ABRE‐binding factors (ABFs) that activate transcription through this cis element. A rice ABF, TRAB1, has been shown to be activated via ABA‐dependent phosphorylation. While a large number of signalling factors have been identified that are involved in stomatal regulation by ABA, relatively less is known about the ABA‐signalling pathway that leads to gene expression. We have shown recently that three members of the rice SnRK2 protein kinase family, SAPK8, SAPK9 and SAPK10, are activated by ABA signal as well as by hyperosmotic stress. Here we show that transient overexpression in cultured cell protoplasts of these ABA‐activated SnRK2 protein kinases leads to the activation of an ABRE‐regulated promoter, suggesting that these kinases are involved in the gene‐regulation pathway of ABA signalling. We further show several lines of evidence that these ABA‐activated SnRK2 protein kinases directly phosphorylate TRAB1 in response to ABA. Kinetic analysis of SAPK10 activation and TRAB1 phosphorylation indicated that the latter immediately followed the former. TRAB1 was found to be phosphorylated not only in response to ABA, but also in response to hyperosmotic stress, which was interpreted as the consequence of phosphorylation of TRAB1 by hyperosmotically activated SAPKs. Physical interaction between TRAB1 and SAPK10 in vivo was demonstrated by a co‐immunoprecipitation experiment. Finally, TRAB1 was phosphorylated in vitro by the ABA‐activated SnRK2 protein kinases at Ser102, which is phosphorylated in vivo in response to ABA and is critical for the activation function. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Plant Journal Wiley

Abscisic acid‐activated SNRK2 protein kinases function in the gene‐regulation pathway of ABA signal transduction by phosphorylating ABA response element‐binding factors

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References (55)

Publisher
Wiley
Copyright
Copyright © 2005 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0960-7412
eISSN
1365-313X
DOI
10.1111/j.1365-313X.2005.02583.x
pmid
16359387
Publisher site
See Article on Publisher Site

Abstract

The plant hormone abscisic acid (ABA) induces gene expression via the ABA‐response element (ABRE) present in the promoters of ABA‐regulated genes. A group of bZIP proteins have been identified as ABRE‐binding factors (ABFs) that activate transcription through this cis element. A rice ABF, TRAB1, has been shown to be activated via ABA‐dependent phosphorylation. While a large number of signalling factors have been identified that are involved in stomatal regulation by ABA, relatively less is known about the ABA‐signalling pathway that leads to gene expression. We have shown recently that three members of the rice SnRK2 protein kinase family, SAPK8, SAPK9 and SAPK10, are activated by ABA signal as well as by hyperosmotic stress. Here we show that transient overexpression in cultured cell protoplasts of these ABA‐activated SnRK2 protein kinases leads to the activation of an ABRE‐regulated promoter, suggesting that these kinases are involved in the gene‐regulation pathway of ABA signalling. We further show several lines of evidence that these ABA‐activated SnRK2 protein kinases directly phosphorylate TRAB1 in response to ABA. Kinetic analysis of SAPK10 activation and TRAB1 phosphorylation indicated that the latter immediately followed the former. TRAB1 was found to be phosphorylated not only in response to ABA, but also in response to hyperosmotic stress, which was interpreted as the consequence of phosphorylation of TRAB1 by hyperosmotically activated SAPKs. Physical interaction between TRAB1 and SAPK10 in vivo was demonstrated by a co‐immunoprecipitation experiment. Finally, TRAB1 was phosphorylated in vitro by the ABA‐activated SnRK2 protein kinases at Ser102, which is phosphorylated in vivo in response to ABA and is critical for the activation function.

Journal

The Plant Journal – Wiley

Published: Dec 1, 2005

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