STRUCTURE-ACTIVITY-RELATIONSHIPS OF CYCLOPENTANE ANALOGS OF JASMONIC ACID FOR INDUCED RESPONSES OF CANOLA SEEDLINGS, BRASSICA-NAPUS L

Jasmonic acid (JA) has potent activity in enhancing cotyledon toughnes s and stimulating the biosynthesis of 3-indolymethyl glucosinolate in seedlings of canola, Brassica napus L. Structure-activity relationship s among cyclopentane analogs of JA revealed that maximum activity in b oth systems was achieved when an acetyl side chain (or a methylated ac etyl side chain) occurred at the C-1 ring position, an n-pentenyl side chain at the C-2 ring position, and a keto group at the C-3 ring posi tion. Although coronatine and coronafacic acid both possess a cyclopen tane ring with a keto group at the C-3 position, only coronatine was a ctive in B. napus seedlings. Coronatine, a chlorosis-inducing toxin es sential to the infectivity of pathovars of Pseudomonas syringae, acted as a complete molecular mimic of JA and had the same stimulatory effe ct on specific indole glucosinolates in Brassica species, thereby cast ing doubt on the hypothesis that indole glucosinolates serve in bacter ial pathogen defense. Similarities and differences for structural requ irements for activity among several diverse physiological systems affe cted by jasmonates likely reflect species-, tissue-, and developmental -specific differences.