Poster: Intracellular Signaling
Abs #
812: Activation of Specific MAP Kinases in Response to Systemin and Other Wound-related Signals in Tomato
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Presenter: |
Holley, Susan , holleys@biol.sc.edu |
Authors | Holley, Susan (A) Stratmann, Johannes (A) | | Affiliations: |
(A): University of South Carolina
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Tomato plants, in response to attacks by herbivorous insects, fungal pathogens, and other mechanical wounding, induce localized and systemic expression of a range of defense-related proteins. Systemin, an 18-amino acid protein released at wound sites by chewing herbivores, is essential for the systemic wound response. Systemin, along with ten other stress signals, has previously been shown to induce 48 kDa mitogen-activated protein kinase (MAPK) activity in Lycopersicon peruvianum suspension-cultured cells as well as in L. esculentum leaves. We found 11 putative MAPKs in the TIGR LeGI database. Therefore, it is possible that multiple MAPKs contribute to the 48 kDa MAPK activity. Here we report the cloning of three MAPKs from a leaf cDNA library derived from plants overexpressing the systemin precursor, prosystemin. LeMPKs 1 and 2 show high homology to each other (95% at the amino acid level) as well as to MAPKs in tobacco, Ntf4 and SIPK. SIPK is responsive to a wide range of stress signals in tobacco while Ntf4 plays a role in developmental processes. LeMPK 3 is homologous to tobacco wound-induced protein kinase (WIPK). Member-specific antibodies were designed to distinguish between the three MAPKs. We used these antibodies to correlate the particular LeMPKs with various stress signals by immunokinase assays. Systemin was shown to activate LeMPKs 1 and 2 with similar kinetics in L. peruvianum suspension-cultured cells and L. esculentum leaves. We also showed that wounding of leaves with a hemostat activates LeMPK 3 in addition to LeMPKs 1 and 2. Moreover, LeMPKs 1 and 2 were activated by four different oligosaccharide elicitors. These results demonstrate that multiple stress signaling pathways in the tomato plant converge at the level of LeMPKs 1 and 2.
