Structure-activity relationships of synthetic analogs of jasmonic acid and coronatine on induction of benzo[c]phenanthridine alkaloid accumulation in Eschscholzia californica cell cultures.

A facile test system based on the accumulation of benzo[c]phenanthridine alkaloids in Eschscholzia californica cell suspension culture (an indicator of defense gene activation) has been used to analyze a series of synthetic compounds for elicitor-like activity. Of the 200 jasmonic acid and coronatine analogs tested with this system, representative results obtained with 49 of them are presented here. The following can be summarized concerning structure-activity relationships: there is a large degree of plasticity allowed at the C-3 of jasmonic acid in the activation of defense genes. The carbonyl moiety is not strictly required, but exocyclic double bond character appears necessary. The pentenyl side chain at C-2 cannot tolerate bulky groups at the terminal carbon and still be biologically active. Substitutions to the C-1' position are tolerated if they can potentially undergo beta-oxidation. Either an alkanoic acid or methyl ester is required at C-1, or a side chain that can be shortened by beta-oxidation or by peptidase hydrolysis. Coronatine and various derivatives thereof are not as effective as jasmonic acid, and derivatives in inducing benzo[c]phenanthridine alkaloid accumulation. Jasmonic acid rather than the octadecanoic precursors is therefore considered to be a likely signal transducer of defense gene activation in planta.