43. イネのジャスモン酸生合成に関わる12-oxophytodienoic acid還元酵素遺伝子の同定

概要

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We have reported that isolation and characterization of a jasmonic acid (JA)-responsive gene, OsOPR1, from suspension-cultured rice cells (Oryza sativa L. cv. BL-1) that encodes 12-oxophytodienoic acid (OPDA) reductase (OPR). OsOPR1 reduced (+)-cis-OPDA, a natural precursor of JA, at high protein concentrations in low yields. On the other hand, three OPRs (AtOPR1, 2, and 3) exist in Arabidopsis thaliana. The enzymatic activity of AtOPR1 and AtOPR2 was similar to OsOPR1, their biological functions being unknown. AtOPR3 that is responsible for biosynthesis of JA has been shown to localize in peroxisomes and reduce (+)-cis-OPDA effectively. In this study, we found that 11 OPR genes exist in rice using a rice (O. sativa L. cv. Nipponbare) genome database recently opened to the public, and that one of these OPRs, tentatively named OPR8, has the peroxisomal targeting signal, as in the case of AtOPR3. OsOPR8 expressed in a functional form in Escherichia coli exhibited AtOPR3- like activity that reduces (+)-cis-OPDA effectively. It was also shown that fusions of OsOPR8 with Green Fluorescent Protein were detected exclusively in peroxisomes of onion epidermal cells. These strongly suggest that OsOPR8 is the OPR responsible for biosynthesis of JA in rice. Expression analysis of OsOPR8 in rice plants as well as the suspension-cultured cells is now under way.
植物化学調節学会の論文
2004-10-13