Activation of the tobacco SIP kinase by both a cell wall-derived carbohydrate elicitor and purified proteinaceous elicitins from Phytophthora spp.
Two purified proteinaceous fungal elicitors, parasiticein (an alpha elicitin) and cryptogein (a beta elicitin), as well as a fungal cell wall-derived carbohydrate elicitor all rapidly activated a 48-kD kinase in tobacco suspension cells. The maximum activation of this kinase paralleled or preceded medium alkalization and activation of the defense gene phenylalanine ammonia-lyase (PAL). In addition, the two elicitins, which also induced hypersensitive cell death, activated a 44- and a 40-kD kinase with delayed kinetics. By contrast, the cell wall-derived elicitor only weakly activated the 44-kD kinase and failed to activate the 40-kD kinase. The size and substrate preference of the 48-kD kinase are reminiscent of the recently purified and cloned salicylic acid-induced protein (SIP) kinase, which is a member of the mitogen-activated protein kinase family. Antibodies raised against a peptide corresponding to the unique N terminus of SIP kinase immunoreacted with the 48-kD kinase activated by all three elicitors from Phytophthora spp. In addition, the cell wall elicitor and the salicylic acid-activated 48-kD kinase copurified through several chromatography steps and comigrated on two-dimensional gels. Based on these results, all three fungal elicitors appear to activate the SIP kinase. In addition, inhibition of SIP kinase activation by kinase inhibitors correlated with the suppression of cell wall elicitor-induced medium alkalization and PAL gene activation, suggesting a regulatory function for the SIP kinase in these defense responses.
Zhang
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Waksman Institute and Department of Molecular Biology and Biochemistry, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, New Jersey 08854-8020, USA.
Du
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Klessig
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D020418:Algal Proteins; D000595:Amino Acid Sequence; D000906:Antibodies / Q000276:immunology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D050260:Carbohydrate Metabolism; D002473:Cell Wall / Q000201:enzymology; D002478:Cells, Cultured; D004789:Enzyme Activation; D005656:Fungal Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D006863:Hydrogen-Ion Concentration; D008562:Membrane Glycoproteins / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases; D008969:Molecular Sequence Data; D010650:Phenylalanine Ammonia-Lyase / Q000235:genetics / Q000378:metabolism; D010838:Phytophthora / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000378:metabolism; D010940:Plant Proteins; D010947:Plants, Toxic; D012459:Salicylates / Q000378:metabolism; D020156:Salicylic Acid; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000201:enzymology* / Q000382:microbiology; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D020418:Algal Proteins; D000906:Antibodies; D005656:Fungal Proteins; D008562:Membrane Glycoproteins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D012459:Salicylates; C061032:cryptogein protein, Phytophthora cryptogea; C110312:elicitor protein, Phytophthora parasitica; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C106405:SA-induced protein kinase; D010650:Phenylalanine Ammonia-Lyase; D020156:Salicylic Acid