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Building a Plant Signaling Molecule

Jasmonic acid is a signaling molecule that regulates a wide range of developmental and defense-related processes in higher plants. It is synthesized from linolenic acid via an enzymatic pathway that begins in the plastid and terminates in peroxisomes. The jasmonic acid precursor 12-oxo-phytodienoic acid is converted in the peroxisome to 3-oxo-2-(2'-[Z]-pentenyl)-cyclopentane-1-octanoic acid (OPC-8:0), which subsequently undergoes three rounds of -oxidation to yield jasmonic acid. Although most jasmonic acid biosynthetic enzymes have been identified, several key steps in the pathway are unknown.

OPC-8:0 CoA Ligase1 is targeted to peroxisomes.

In this Paper of the Week, Abraham J. K. Koo and colleagues use co-expression analysis to identify genes that are coordinately regulated with known jasmonic acid biosynthetic components in Arabidopsis. Among the candidate genes uncovered by this approach is a 4-coumarate:CoA ligase-like member of the acyl-activating enzyme gene family that the authors named OPC-8:0 CoA Ligase1. Using a combination of genetic, biochemical, and cellular evidence, Koo et al. show that OPC-8:0 CoA Ligase1 is involved in peroxisomal jasmonic acid biosynthesis. These findings establish a clear physiological role for OPC-8:0 CoA Ligase1 in the activation of jasmonic acid biosynthetic precursors and indicate that OPC-8:0 is a physiological substrate for the activation step. As a result, this study provides a further understanding of the biosynthetic pathway of this important plant signaling molecule.

FOOTNOTES

See referenced article, J. Biol. Chem. 2006, 281, 33511-33520

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