The homeodomain-leucine zipper (HD-Zip) class I transcription factors ATHB7 and ATHB12 modulate abscisic acid signalling
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The homeodomain-leucine zipper (HD-Zip) class I transcription factors ATHB7 and ATHB12 modulate abscisic acid signalling by regulating protein phosphatase 2C and abscisic acid receptor gene activities ¨ verna¨s • Henrik Johansson Ana Elisa Valde´s • Elin O Alvaro Rada-Iglesias • Peter Engstro¨m
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Received: 3 April 2012 / Accepted: 16 August 2012 Ó Springer Science+Business Media B.V. 2012
Abstract Plants perceiving drought activate multiple responses to improve survival, including large-scale alterations in gene expression. This article reports on the roles in the drought response of two Arabidopsis thaliana homeodomain-leucine zipper class I genes; ATHB7 and ATHB12, both strongly induced by water-deficit and abscisic acid (ABA). ABA-mediated transcriptional regulation of both genes is shown to depend on the activity of protein phosphatases type 2C (PP2C). ATHB7 and ATHB12 are, thus, targets of the ABA signalling mechanism defined by the PP2Cs and the PYR/PYL family of ABA receptors, with which the PP2C proteins interact. Our results from chromatin immunoprecipitation and gene expression analyses demonstrate that ATHB7 and ATHB12 act as positive transcriptional regulators of PP2C genes, and thereby as negative regulators of abscisic acid signalling. In support of this notion, our results also show that ATHB7 and ATHB12 act to repress the transcription of genes encoding the ABA receptors PYL5 and PYL8 in response to an ABA stimulus. In summary, we demonstrate that ATHB7 and ATHB12 have essential functions in the primary response
Electronic supplementary material The online version of this article (doi:10.1007/s11103-012-9956-4) contains supplementary material, which is available to authorized users. ¨ verna¨s H. Johansson P. Engstro¨m A. E. Valde´s (&) E. O Physiological Botany, Uppsala BioCenter, Uppsala University, Almas Alle´ 5, 75651 Uppsala, Sweden e-mail: [email protected] A. E. Valde´s P. Engstro¨m Linnean Center for Plant Biology, Uppsala, Sweden A. Rada-Iglesias Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA, USA
to drought, as mediators of a negative feedback effect on ABA signalling in the plant response to water deficit. Keywords HD-Zip PP2C ABA SnRK2 ABA receptors Drought stress response
Introduction Plants perceive changes in water availability and respond by specific adaptive alterations in physiology, growth and development, aimed at the efficient use of water resources. Limiting water conditions, or drought, elicit a signalling cascade, to a large extent dependent on abscisic acid (ABA) as a systemic mediator that eventually activates genes involved in the stress adaptive process (Xiong et al. 2002; Shinozaki et al. 2003). Several categories of transcriptional regulators participate in the signal transduction network from perception of drought stress signals to stressresponsive gene expression (Bray 2004). Among these, members of the plant-specific homeodomain-leucine zipper (HD-Zip) class I gene family have roles rela
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