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Positive and negative cross-talk in pathways of resistance to pathogens and insects.
Bostock, Richard1,2, Weyman, Philip 1, Karban, Richard1, Hoegger, Patrik1,2, Lincoln, James1,2, Pan, Zhiqiang1,2, Fan, Xiaohong1,2, Gilchrist, David1,2, 1 2
ABSTRACT- Simultaneous challenge of plants by pathogens and insects can trigger multiple responses that may be beneficial or detrimental to the plant. Host resistance mechanisms are context dependent, influenced by the mix of signals generated by exposure of the plant to various environmental factors and stresses that can occur at a given time. An understanding of the signaling systems that regulate the expression of inducible responses could optimize the utilization of these responses in crop protection. Both positive and negative crosstalk occurs during plant responses to pathogens and insects, and much of the research on defense signaling has focused on salicylate- and jasmonate-mediated responses. We will review our results using tomato (Lycopersicon esculentum) in greenhouse and field studies that illustrate a trade-off between salicylate- and jasmonate-mediated signaling, and will discuss research on strategies to minimize the trade-off that can occur following the application of chemical elicitors of resistance such as acibenzolar and jasmonic acid. In addition, we have evidence of another signaling system that mediates endogenous levels of ceramide in the plant, and will report on progress towards characterization of potential ceramide targets in the cell. Altered ceramide levels are associated with programmed cell death and protection of tomato against the fungal pathogen Alternaria alternata f. sp. lycopersici and sphinganine-analog mycotoxins produced by this and other pathogenic fungi.
KEY WORDS: salicylic acid, jasmonic acid, induced resistance, apoptosis