JXB Advance Access originally published online on August 28, 2007
Journal of Experimental Botany 2007 58(11):2969-2981; doi:10.1093/jxb/erm144
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© 2007 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)
RESEARCH PAPER |
AtMEK1 mediates stress-induced gene expression of CAT1 catalase by triggering H2O2 production in Arabidopsis
1Department of Biology, Hong Kong Baptist University, Hong Kong, China
2College of Agronomy and Biotechnology, China Agricultural University, Beijing, China
* To whom correspondence should be addressed. E-mail: jzhang{at}hkbu.edu.hk; E-mail: jiaws{at}cau.edu.cn
Catalase and hydrogen peroxide (H2O2) have been extensively studied for their roles in various stress responses. However, little is known about the triggering mechanisms for stress-induced catalase gene expression or about H2O2 production as a stress signal. It is reported here that ABA-, drought-, and salt stress-induced gene expression of CAT1 catalase is mediated by AtMEK1, an Arabidopsis MAPK kinase, by triggering H2O2 signal production. Both CAT1 expression and AtMEK1 activity were activated by ABA, drought, and salt stresses. The mek1 mutant totally blocked stress-induced CAT1 expression and, interestingly, stress-induced H2O2 production was also blocked. Over-expression of AtMEK1 significantly promoted stress-induced CAT1 expression, and also promoted H2O2 production. These results conclusively indicate that stress-induced CAT1 expression is mediated by AtMEK1 and, furthermore, that the triggering of H2O2 production might be involved in this process, as further proved by the observation that CAT1 expression was induced by applied H2O2. Surprisingly, the signalling mechanisms for stress-induced gene expression of CAT2 and CAT3 were very different from that of CAT1. Except for drought stress, expression of CAT2 or CAT3 was also activated by salt stress or ABA treatment, and AtMEK1 was not proved to be involved in the drought-induced expression of CAT2 or CAT3. Further studies showed that stomatal movement was much less sensitive to ABA in AtMEK1 mutant (mek1), and over-expression of AtMEK1 in Arabidopsis increased plant resistance to drought or salt stress, which further demonstrated that AtMEK1 is a crucial mediator in plant stress signal transduction.
Key words: ABA, catalase, drought, hydrogen peroxide, MAPK kinases, salt stress
Received 5 March 2007; Revised 28 May 2007 Accepted 30 May 2007
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