Metabolite-based Defense Mechanisms

The Phytophthora-derived oligopeptide elicitor, Pep-13, originally identified as an inducer of plant defense in the nonhost–pathogen interaction of parsley and Phytophthora sojae, triggers defense responses in potato. In cultured potato cells, Pep-13 treatment results in an oxidative burst and activation of defense genes. Infiltration of Pep-13 into leaves of potato plants induces the accumulation of hydrogen peroxide, defense gene expression and the accumulation of jasmonic and salicylic acids. Derivatives of Pep-13 show similar elicitor activity in parsley and potato, suggesting a receptor-mediated induction of defense response in potato similar to that observed in parsley. However, unlike in parsley, infiltration of Pep-13 into leaves leads to the development of hypersensitive response-like cell death in potato. Interestingly, Pep-13-induced necrosis formation, hydrogen peroxide formation and accumulation of jasmonic acid, but not activation of a subset of defense genes, is dependent on salicylic acid, as shown by infiltration of Pep-13 into leaves of potato plants unable to accumulate salicylic acid. Thus, in a host plant of Phytophthora infestans, Pep-13 is able to elicit salicylic acid-dependent and -independent defense responses.

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