| Summary: | 碩士 === 臺灣大學 === 植物科學研究所 === 98 === Calcium-dependent protein kinases (CDPKs) play important roles in the Ca2+ signal transduction in plants. CDPKs activated by Ca2+ signal phosphorylate proteins involved in the Ca2+ signal transduction. According to the phylogenetic analysis of 34 CDPKs and 8 CRKs (CDPK-related kinase) in Arabidopsis thaliana, CDPKs were divided into 4 subgroups, and there is the similarity among the CDPKs of subgroup IV and CRKs. This study includes the CDPKs and CRKs of other species, and showed the similar result. Moreover, the phylogenetic analysis of the domains also divided into 4 subgroups. The result of grouping is consistent in planta. In a previous study, the Arabidopsis thaliana AtDi19 (drought-induced protein 19) protein was found to be the substrate of CDPK. The AtDi19 gene family encodes 7 proteins, AtDi19-1~7, which contain two zinc-finger like motifs. AtDi19-2 could be involved in the salt stress response. Based on another research, Ser109 is the phosphorylation site of the AtDi19-2, namely AtDi19-2-2. In particular, AtDi19-2-2 was only phosphorylated by AtCPK16 but not by other CDPKs. The result showed the substrate specificity of CDPKs. In order to identify which amino acids are important for the recognition of AtCPK16, site-directed mutagenesis of fusion peptide containing the phosphorylation site revealed that -1~+2 amino acids next to Ser109 are important for the recognition. In addition, we discovered two additional substrates of Arabidopsis CDPKs, Arabidopsis ACC synthase 5 and 7 (AtACS5, AtACS7).
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