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Molecular and biochemical characterization of LeCRK1, a ripening-associated tomato CDPK-related kinase

Leclercq, Julie and Ranty, Benoît and Sanchez-Ballesta, Maria Teresa and Li, Zhengguo and Jones, Brian and Jauneau, Alain and Pech, Jean-Claude and Latché, Alain and Ranjeva, Raoul and Bouzayen, Mondher Molecular and biochemical characterization of LeCRK1, a ripening-associated tomato CDPK-related kinase. (2005) Journal of Experimental Botany, vol. 5 (n° 409). pp. 25-35. ISSN 0022-0957

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Official URL: http://dx.doi.org/10.1093/jxb/eri003

Abstract

A cDNA clone (LeCRK1), encoding a novel isoform of calcium-dependent protein kinase (CDPK), was isolated by screening a tomato (Lycopersicon esculentum) cDNA library. The protein derived from the full-length sequence indicated that it belongs to the family of CDPK-related kinases (CRKs) and the predicted amino acid sequence shows a modular organization of the protein consisting of different characteristic domains. The kinase domain of LeCRK1 shares a high degree of similarity with the catalytic domain of CDPKs. In contrast to canonical members of the family, LeCRK1 has a degenerate sequence in the C-terminal calmodulinlike domain. LeCRK1 protein was shown to be a functional kinase, but, consistent with the lack of calciumbinding activity, its autophosphorylation activity did not require calcium. LeCRK1 harbours an amphiphilic amino acid region revealed to be a functional calmodulinbinding site by in vitro assay. A putative myristoylation/ palmitoylation sequence has been identified at the N-terminus. Expressing an LeCRK1::GFP fusion protein in the protoplast resulted in its targeting to the plasma membrane. Site-directed mutagenesis of critical amino acids of the myristoylation/palmitoylation consensus sites led to the accumulation of the mutated protein in the cytoplasm, suggesting that the native protein is anchored to the plasma membrane by acylated residues. Expression studies revealed significant accumulation of LeCRK1 transcripts during fruit ripening, although transcripts were also detected in stem, leaf, and flower. LeCRK1 mRNA level in leaves was slightly induced by ethylene and salicylic acid, and upon mechanical wounding and cold treatment. It is noteworthy that LeCRK1 mRNAs were undetectable in different tomato-ripening natural mutants such as NR, Rin, and Nor, suggesting a role in the ripening process.

Item Type:Article
Additional Information:The definitive version is available at http://jxb.oxfordjournals.org/ The original PDF of the article can be found at Journal of Experimental Botany website : http://jxb.oxfordjournals.org/cgi/content/abstract/56/409/25
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Institut National de la Recherche Agronomique - INRA
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT
Université de Toulouse > Université Paul Sabatier-Toulouse III - UPS
French research institutions > Centre National de la Recherche Scientifique - CNRS
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Deposited By: Dabernat Séverine
Deposited On:03 Dec 2008 08:40

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