Partially N-Deacetylated Chitin Elicitor Induces Antimicrobial Flavonoids in Pea Epicotyls

Kohki Akiyama*, Kazuyoshi Kawazu and Akio Kobayashi Department of Agricultural Science, Okayama University, Okayama 700, Japan Z. Naturforsch. 49c, 811-818 (1994); received July 12, 1994 Elicitor, Chitin, Chitosan, Flavonoid, Pisum sativum Pisatin elicitors including fragments of chitosan and partially N-deacetylated chitins (DACs) strongly induced (+)-a,2',4,4'-tetrahydroxydihydrochalcone, (-)-4',7-dihydroxyflavanone, and 4,4'-dihydroxy-2'-methoxychalcone in Pisum sativum. These three flavonoids with moderate or weak antimicrobial activities were effectively induced by the treatment of pea with either the biotic elicitors or an abiotic elicitor CuCl2. The examination of chitosan derivatives with different molecular size and different N-acetylation for the flavonoidinducing activity in pea epicotyl assay revealed that the structural features required for the flavonoids induction were different from those required for (+)-pisatin induction. (+)-2Hydroxypisatin, a possible intermediate in pisatin degradation pathway, which has been iso­ lated from pea seedlings treated with the abiotic elicitor or infected by fungi was not induced by the chitosaccharides in pea epicotyl assay. These findings suggest that pea plants could distinguish invading pathogens by the difference of structural features of chitosaccharides derived from chitin, a major constituent of fungal cell walls. Thereby, the plant could accu­ mulate antimicrobial compounds responsible for the chemical defense against invading pathogens.