Isolation and functional identification of Jasmonte resistant 1, a Jasmonic acid isoleucine-conjugating enzyme in...

Jasmonate resistant 1 (JAR1), which encodes a jasmonate-amino synthase, mediates the biosynthesis of jasmonoyl-isoleucine (JA-Ile), the bioactive form of jasmonate involved in JA signal transduction pathway. Although JAR1 has been characterized in several plant species, its regulatory function in mediating JA signaling to modulate the biosynthesis of terpenoid indole alkaloids (TIAs) in Catharanthus roseus, a medicinal and ornamental plant, have not been previously investigated. In this study, we have identified and cloned CrJAR1, a member of the Gretchen Hagen3 (GH3) gene family, from C. roseus and confirmed its enzymatic activity in JA-Ile formation via heterologous expression in E. coli. Functional analyses using transient overexpression and virus-induced gene silencing (VIGS) in C. roseus leaves revealed that CrJAR1 positively regulates the accumulation of catharanthine and vindoline. Moreover, we demonstrated that CrCOI1, the jasmonate receptor, functions synergistically with CrJAR1 in modulating TIA biosynthesis. Co-silencing of CrCOI1 and CrJAR1 resulted in a lower sensitivity to exogenous JA treatment compared to silencing of CrJAR1 alone, indicating distinct yet complementary roles in jasmonate-mediated metabolic regulation. These results advance our understanding the function of CrJAR1 and offer new strategies for engineering specialized metabolite biosynthesis in plants.