Elicitor- and A23187-induced expression of WCK-1, a gene encoding mitogen-activated protein kinase in wheat.
Wheat cultured cells were used to study the role of Ca2+ in regulating protein kinases during the induction of defense-related genes by fungal elicitor treatments. Manipulation of intracellular Ca2+ concentrations by treatment with calcium ionophore A23187 in the presence of high extracellular Ca2+ resulted in the induction of mRNA expression of WCK-1, a gene encoding mitogen-activated protein (MAP) kinase. The induction of WCK-1 mRNA by A23187 did not occur when extracellular Ca2+ was chelated by 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). The WCK-1 mRNA was also induced by Typhula ishikariensis-derived elicitors, suggesting a possible involvement of WCK-1 in the plant defense response against pathogens. BAPTA and a calcium channel blocker, La3+, inhibited the elicitor-induced expression of the WCK-1 mRNA. A recombinant fusion protein of WCK-1 (GST-WCK-1) autophosphorylated at the Tyr residue and exhibited an autophosphorylation-dependent protein kinase activity towards myelin basic protein. Alteration of Tyr-196 in the conserved 'TEY' motif in GST-WCK-1 to Phe by site-directed mutagenesis abolished the autophosphorylation. The GST-WCK-1 protein was activated by elicitor-treated wheat cell extracts but not by the control extract. These results suggest that fungal elicitors activate WCK-1, a specific MAP kinase in wheat. Furthermore, the results suggest a possible involvement of Ca2+ in enhancing the MAP kinase signaling cascade in plants by controlling the levels of the MAP kinase transcripts.
Takezawa
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Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan.
D000595:Amino Acid Sequence; D001483:Base Sequence; D001487:Basidiomycota / Q000737:chemistry* / Q000254:growth & development; D000001:Calcimycin / Q000494:pharmacology*; D002614:Chelating Agents / Q000494:pharmacology; D017077:Culture Media, Conditioned / Q000737:chemistry / Q000494:pharmacology; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics*; D005982:Glutathione Transferase / Q000235:genetics; D007476:Ionophores / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics*; D008969:Molecular Sequence Data; D010940:Plant Proteins; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014908:Triticum / Q000166:cytology / Q000201:enzymology / Q000235:genetics*
D002614:Chelating Agents; D017077:Culture Media, Conditioned; D018076:DNA, Complementary; D007476:Ionophores; D010940:Plant Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D000001:Calcimycin; D004533:Egtazic Acid; D005982:Glutathione Transferase; D020928:Mitogen-Activated Protein Kinases; C122163:WCK-1 protein, Triticum aestivum; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid