Biosynthesis of oat avenanthramide phytoalexins

Abstract

The biosynthesis of oat phytoalexins, avenanthramides, was investigated by administering labeled putative precursors to oat leaf segments treated with the elicitor, penta-N-acetylchitopentaose. Among the compounds tested, oat leaf segments incorporated [ring-UL-14C]anthranilic acid, [2,3,4,5,6-2H]l-phenylalanine and [1,2-13C]p-coumaric acid into avenanthramides, but not [2,6-2H]l-tyrosine. These findings suggested that avenanthramides were de novo synthesized from primary metabolites after elicitor treatment and that phenylpropanoid metabolism is involved in their biosynthesis. In addition to l-phenylalanine and p-coumaric acid, sodium [13C2]acetate was incorporated into avenanthramide L, which indicated that the avenalumoyl (5-(4-hydroxyphenyl)-2,4-pentadienoyl) moiety of avenanthramide L was biosynthesized from p-coumaric acid by elongation of its side chain with an acetate unit.