Localization of the Raf-like Kinase CTR1 to the Endoplasmic Reticulum of Arabidopsis through Participation in Ethylene Receptor Signaling Complexes*
- Zhiyong Gao‡§,
- Yi-Feng Chen‡§,
- Melynda D. Randlett‡,
- Xue-Chu Zhao‡,
- Jennifer L. Findell‡,
- Joseph J. Kieber¶ and
- G. Eric Schaller‡§∥
- ‡Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham, New Hampshire 03824 and the ¶Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599
- ∥ To whom correspondence should be addressed: Dept. of Biological Sciences, Dartmouth College, Hanover, NH 03755. Tel.: 603-646-2525; Fax: 603-646-1347; E-mail: george.e.schaller{at}dartmouth.edu.
Abstract
The plant hormone ethylene is perceived by a five-member family of receptors related to the bacterial histidine kinases. The Raf-like kinase CTR1 functions downstream of the ethylene receptors as a negative regulator of ethylene signal transduction. CTR1 is shown here to be associated with membranes of the endoplasmic reticulum in Arabidopsis as a result of its interactions with ethylene receptors. Membrane association of CTR1 is reduced by mutations that eliminate ethylene receptors and by a mutation in CTR1 that reduces its ability to bind to the ethylene receptor ETR1. Direct evidence that CTR1 is part of an ethylene receptor signaling complex was obtained by co-purification of the ethylene receptor ETR1 with a tagged version of CTR1 from an Arabidopsis membrane extract. The histidine kinase activity of ETR1 is not required for its association with CTR1, based on co-purification of tagged ETR1 mutants and CTR1 after expression in a transgenic yeast system. These data demonstrate that CTR1 is part of an ethylene receptor signaling complex in Arabidopsis and support a model in which localization of CTR1 to the endoplasmic reticulum is necessary for its function. Additional data that demonstrate a post-transcriptional effect of ethylene upon the expression of CTR1 suggest that production of ethylene receptor signaling complexes may be coordinately regulated.
Footnotes
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↵1 The abbreviations used are: ER, endoplasmic reticulum; ACC, 1-aminocyclopropane-1-carboxylic acid; GST, glutathione S-transferase; PM, plasma membrane.
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↵* This work was supported by National Science Foundation Grants MCB-9982510 and MCB-0235450 (to G. E. S.) and MCB-9816914 (to J. J. K.). This is Scientific Contribution Number 2187 from the New Hampshire Agricultural Experiment Station. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵§ Current address: Dept. of Biological Sciences, Dartmouth College, Hanover, NH 03755.
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- Received May 27, 2003.
- Revision received June 18, 2003.
- The American Society for Biochemistry and Molecular Biology, Inc.
