Inhibition by Salicylhydroxamic Acid, BW755C, Eicosatetraynoic Acid, and Disulfiram of Hypersensitive Resistance Elicited by Arachidonic Acid or Poly-l-Lysine in Potato Tuber

Abstract

The hypothesis that arachidonic acid (AA) [a metabolite of Phytophthora infestans] induction of sesquiterpene accumulation and browning in potato (Solanum tuberosum) is mediated by a lipoxygenase metabolite of AA was tested using lipoxygenase inhibitors. Salicylhydroxamic acid (SHAM) and 3-amino-1-(3-trifluoro-methylphenyl)-2-pyrazoline hydrochloride (BW755C) delayed the response to AA. Inhibition by eicosatetraynoic acid (ETYA) was more persistent. These results are consistent with previous reports that SHAM and BW755C are reversible inhibitors of lipoxygenase and easily oxidized by potato while ETYA acts as an irreversible inhibitor. Disulfiram (tetraethylthiuram disulfide) also inhibited AA elicitor activity. SHAM was most effective if applied at the time of AA treatment, having no effect if applied 6 hours afterward. SHAM was effective in the presence of MES or MOPS buffers but not in acetate-buffered or unbuffered solutions; neither BW755C nor ETYA exhibited this restriction. However, SHAM, BW755C, and ETYA also were inhibitors of browning and sesquiterpene accumulation elicited in potato by poly-L-lysine, which, unlike AA, is not a lipoxygenase substrate. SHAM effectiveness also was restricted to 6 hours after treatment with poly-L-lysine. While the results with AA support a role for lipoxygenase, those with poly-L-lysine may be evidence that these compounds are having other effects in potato tissue.