ABSTRACT
The isoleucine conjugate of 12-oxo-phytodienoic acid (OPDA-Ile), a new member of the jasmonate family, was recently identified in Arabidopsis thaliana and might be a signaling molecule in plants. However, the biosynthesis and function of OPDA-Ile remains elusive. This study reports an in vitro enzymatic method for synthesizing OPDA-Ile, which is catalyzed by reactions of lipoxygenase (LOX), allene oxide synthase (AOS), and allene oxide cyclase (AOC) using isoleucine conjugates of α -linolenic acid (LA-Ile) as the substrate. A. thaliana fed LA-Ile exhibited a marked increase in the OPDA-Ile concentration. LA-Ile was also detected in A. thaliana. Furthermore, stable isotope labelled LA-Ile was incorporated into OPDA-Ile. Thus, OPDA-Ile is biosynthesized via the cyclization of LA-Ile in A. thaliana.
Subject(s)
Fatty Acids, Unsaturated/biosynthesis , Intramolecular Oxidoreductases/metabolism , Isoleucine/biosynthesis , Lipoxygenase/metabolism , alpha-Linolenic Acid/metabolism , Arabidopsis/chemistry , Cyclization , Fatty Acids, Unsaturated/chemistry , Isoleucine/chemistry , Molecular Structure , alpha-Linolenic Acid/chemistryABSTRACT
It has been reported that treatment with yeast cell wall extract (YCWE) induces PDF1 and PR-1 gene expression; these transcripts are important markers of plant disease resistance, though the detailed signaling mechanisms that induce these defense responses are still unknown. In this report, we found that YCWE treatment triggered rice cell suspension cultures to accumulate phenylalanine (Phe), cis-12-oxo-phytodienoic acid (OPDA), 12-hydroxyjasmonoyle isoleucine (12OHJA-Ile), and azelaic acid (AzA). YCWE treatment also reduced endogenous triacylglycerol (TG) content. The addition of 13C-uniform-labeled oleic, linoleic and linolenic acids to the rice cell suspension cultures gave rise to 13C-uniform-labeled AzA. It was also found that YCWE treatment for Arabidopsis thaliana resulted in accumulations of OPDA, AzA, Phe, and camalexin together with enhanced resistance against Botrytis cinerea infection. This suggested that YCWE treatment upon plants may activate JA and AzA signaling systems to induce plant disease resistance.
