Two genes that encode Ca2+-dependent protein kinases are induced by drought and high-salt stresses in Arabidopsis thaliana |
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Authors: | Takeshi Urao Takeshi Katagiri Tsuyoshi Mizoguchi Kazuko Yamaguchi-Shinozaki Nobuaki Hayashida and Kazuo Shinozaki |
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Institution: | (1) Laboratory of Plant Molecular Biology, The Institute of Physical and Chemical Research (RIKEN), Tsukuba Life Science Center, 3-1-1, Koyadai, Tsukuba, 305 Ibaraki, Japan;(2) Tsukuba Research Laboratory, DAIDO HOXAN Inc., 3-16-2 Ninomiya, 305 Tsukuba, Ibaraki, Japan;(3) Institute of Biological Sciences, The University of Tsukuba, Tennohdai, Tsukuba, 305 Ibaraki, Japan;(4) Biological Resources Division, Japan International Research Center for Agricultural Sciences, Ohwashi 1-2, Tsukuba, 305 Ibaraki, Japan |
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Abstract: | Two cDNA clones, AATCDPK1 and cATCDPK2, encoding Ca2+-dependent, calmodulin-independent protein kinases (CDPK) were cloned from Arabidopsis thaliana and their nucleotide sequences were determined. Northern blot analysis indicated that the mRNAs corresponding to the ATCDPK1 and ATCDPK2 genes are rapidly induced by drought and high-salt stress but not by low-temperature stress or heat stress. Treatment of Arabidopsis plants with exogenous abscisic acid (ABA) had no effect on the induction of ATCDPK1 or ATCDPK2. These findings suggest that a change in the osmotic potential of the environment can serve as a trigger for the induction of ATCDPK1 and ATCDPK2. Putative proteins encoded by ATCDPK1 and ATCDPK2 which contain open reading frames of 1479 and 1488 bp, respectively, are designated ATCDPK1 and ATCDPK2 and show 52% identity at the amino acid sequence level. ATCDPK1 and ATCDPK2 exhibit significant similarity to a soybean CDPK (51 % and 73%, respectively). Both proteins contain a catalytic domain that is typical of serine/threonine protein kinases and a regulatory domain that is homologous to the Ca2+-binding sites of calmodulin. Genomic Southern blot analysis suggests the existence of a few additional genes that are related to ATCDPK1 and ATCDPK2 in the Arabidopsis genome. The ATCDPK2 protein expressed in Escherichia coli was found to phosphorylate casein and myelin basic protein preferentially, relative to a histone substrate, and required Ca2+ for activation. |
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Keywords: | Arabidopsis thaliana Protein kinase Water stress Ca2+-dependent activity |
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