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Activation of the Tobacco SIP Kinase by Both a Cell Wall-Derived Carbohydrate Elicitor and Purified Proteinaceous Elicitins from Phytophthora spp

Shuqun Zhang, He Du and Daniel F. Klessig
The Plant Cell
Vol. 10, No. 3 (Mar., 1998), pp. 435-449
DOI: 10.2307/3870600
Stable URL: http://www.jstor.org/stable/3870600
Page Count: 15
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Activation of the Tobacco SIP Kinase by Both a Cell Wall-Derived Carbohydrate Elicitor and Purified Proteinaceous Elicitins from Phytophthora spp
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Abstract

Two purified proteinaceous fungal elicitors, parasiticein (an α elicitin) and cryptogein (a β 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 twodimensional 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.

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