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First published online October 1, 2004; 10.1104/pp.103.034686 Plant Physiology 136:2971-2981 (2004) © 2004 American Society of Plant Biologists Evidence for Serine/Threonine and Histidine Kinase Activity in the Tobacco Ethylene Receptor Protein NTHK21National Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
Ethylene plays important roles in plant growth, development, and stress responses. Two ethylene receptors, ETR1 from Arabidopsis and NTHK1 from tobacco (Nicotiana tabacum), have been found to have His kinase (HK) activity and Ser/Thr kinase activity, respectively, although both show similarity to bacterial two-component HK. Here, we report the characterization of another ethylene receptor homolog gene, NTHK2, from tobacco. This gene also encodes a HK-like protein and is induced by dehydration and CaCl2 but not significantly affected by NaCl and abscisic acid treatments. The biochemical properties of the yeast (Schizosaccharomyces pombe)-expressed NTHK2 domains were further characterized. We found that NTHK2 possessed Ser/Thr kinase activity in the presence of Mn2+ and had HK activity in the presence of Ca2+. Several lines of evidence supported this conclusion, including hydrolytic stability, phosphoamino acid analysis, mutation, deletion, and substrate analysis. These properties have implications in elucidation of the complexity of the ethylene signal transduction pathway and understanding of ethylene functions in plants.
1 This work was supported by the National Basic Research Project (grant no. G19990117003), the National High-Tech program of China (grant nos. 2001AA222131, 2002AA2Z1001, and 2001AA212121), the National Transgenic Research Project (grant no. JY03A1002), and the National Natural Science Foundation of China (grant no. 30370130). 2 These authors contributed equally to the paper. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.103.034686. * Corresponding author; e-mail jszhang{at}genetics.ac.cn; fax 861064873428. * Corresponding author; e-mail sychen{at}genetics.ac.cn; fax 861064873428. Received October 13, 2003; returned for revision August 29, 2004; accepted September 9, 2004. This article has been cited by other articles:
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