Ion channel-forming alamethicin is a potent elicitor of volatile biosynthesis and tendril coiling. Cross talk between jasmonate and salicylate signaling in lima bean

Alamethicin (ALA), a voltage-gated, ion channel-forming peptide mixture fro m Trichoderma viride, is a potent elicitor of the biosynthesis of volatile compounds in lima bean (Phaseolus lunatus). Unlike elicitation with jasmoni c acid or herbivore damage, the blend of substances emitted comprises only the two homoterpenes, 4,11-dimethylnona-1,3,7-triene and 4,8,12-trimethyltr ideca-1,3,7,11-tetraene and methyl salicylate. Inhibition of octadecanoid s ignaling by aristolochic acid and phenidone as well as mass spectrometric a nalysis of endogenous jasmonate demonstrate that ALA induces the biosynthes is of volatile compounds principally via the octadecanoid-signaling pathway (20-fold increase of jasmonic acid). ALA also up-regulates salicylate bios ynthesis, and the time course of the production of endogenous salicylate co rrelates well with the appearance of the methyl ester in the gas phase. The massive up-regulation of the SA-pathway (90-fold) interferes with steps in the biosynthetic pathway downstream of 12-oxophytodienoic acid and thereby reduces the pattern of emitted volatiles to compounds previously shown to be induced by early octadecanoids. ALA also induces tendril coiling in vari ous species like Pisum, Lathyrus, and Bryonia, but the response appears to be independent from octadecanoid biosynthesis, because inhibitors of lipoxy genase and phospholipase A(2) do not prevent the coiling reaction.