Expression of allene oxide synthase and allene oxide cyclase in the interactions between pea and fungal pathogens

Abstract

Allene oxide synthase (AOS) and allene oxide cyclase (AOC) are enzymes in the octadecanoid pathway that lead to jasmonate (jasmonic acid and methyljasmonic acid) biosynthesis. Pea AOS and AOC cDNAs were isolated by the reverse transcriptase-mediated polymerase chain reaction method with degenerated primers. Treatment of pea epicotyls with suppressor alone or suppressor plus elicitor induced an increase in AOS mRNA 5 h after treatment. AOS was also induced by a virulent pathogen, Mycosphaerella pinodes, 12 h after inoculation but not by a nonpathogen, Ascochyta rabiei, or the fungal elicitor. On the other hand, AOC mRNA accumulation was not significantly affected by treatment with elicitor or suppressor or by inoculations with M. pinodes or A. rabiei. Previously, we observed that gene expression of oxophytodienoic acid reductase (OPR), an enzyme in the octadecanoid pathway, was induced in the pea by suppressor treatment and inoculation of a compatible pathogen. Thus, it is likely that, in addition to OPR, activation of AOS gene expression contributes to the establishment of compatibility.