Synthesis of 12-hydroxyjasmonoyl-l-isoleucine and its isomers and their biological activity against rice

Jasmonate is a plant hormone that regulates development and defense responses. Jasmonoyl-l-isoleucine (JA-Ile) is a ligand for the most studied jasmonate co-receptor, COI1-JAZ, in seed plants. 12-Oxygenation to 12-hydroxyjasmonoyl-l-isoleucine (12-OH-JA-Ile) is a major metabolic pathway of JA-Ile. Moreover, 12-OH-JA-Ile is a selective ligand for some COI1-JAZ pairs in Arabidopsis thaliana. However, few studies have reported on the activity of 12-OH-JA-Ile in rice (Oryza sativa L.). In this study, we synthesized 12-OH-JA-Ile and its isomers, and evaluated their biological activities against rice. 12-OH-JA-Ile inhibited root elongation but did not induce the biosynthesis of momilactone A, a phytoalexin. These results suggested that 12-OH-JA-Ile selectively induced a jasmonate response in rice. The bioactivity of the E-isomer of 12-OH-JA-Ile revealed that the Z-olefin was necessary for root inhibitory activity.