Homologs of old yellow enzyme in plants

Abstract

Old Yellow Enzyme (OYE) is a flavin mononucleotide-dependent oxidoreductase. 12-oxophytodienoic acid reductases (OPRs) are OYE homologs and are represented by multigene families in plants. OPRs catalyze the reduction of double bonds in α,β-unsaturated aldehydes or ketones. They belong to the octadecanoid pathway, which converts linolenic acid to jasmonic acid (JA). Individual OPR family members may have distinct functions due to their different substrate specificity, subcellular localization, tissue distribution, and differential regulation of their expression in response to specific environmental cues. Based on their differential preferences for 12-oxophytodienoate (OPDA) stereoisomers, these enzymes are classified into two subgroups: OPRI and OPRII. OPRI enzymes preferentially catalyze the reduction of cis-(-)OPDA over the JA precursor cis-(+)OPDA , and therefore, they are not involved in JA biosynthesis. Although a significant progress has been made to understand the exact physiological roles of OPR enzymes, the function of OPRI subgroup members in plants remains largely unknown. Enzymes belonging to this subgroup are possibly involved in defense responses and signaling. The members of the OPRII subgroup are required for JA biosynthesis because they catalyze the reduction of the JA precursor cis-(+)OPDA. This review will highlight some characteristics of this family in Arabidopsis and other species and discuss the physiological role of OPR family members in plants.