Studies On The Molecular Mechanism For Jasmonate Perception

Jasmonates (JAs) are a class of plant hormones, which are derived from linolenic acid and characterized by a pentacyclic ring structure, and play indispensable roles in plant defense and development. CORONATINE INSENSITIVE 1 (COI1), an F-box protein essential for the jasmonate responses, interacts with multiple proteins including ASK, AtCUL1, AtRbx1 to form an E3 ubiquitin ligase known as the SCF^COI1 complex, and recruits jasmonate ZIM-domain (JAZ) proteins for degradation by the 26S proteasome. Jasmonoyl-isoleucine (JA-Ile) or coronatine (COR) is essential for the interaction between SCF^COI1 and JAZ proteins and perceived by the SCF^COI1-JAZ complex. However, it was unknown which protein within this complex functions as the JA-Ile/COR receptor.In this study, we built a high-quality structural model of COI1 and performed molecular modeling of COI1-jasmonate interactions. Our results imply that COI1 has the structural traits for binding JA-Ile or COR. The direct binding of these molecules with COI1 was further examined using a combination of molecular and biochemical approaches. Firstly, we used the immobilized jasmonate approach to show that the COI1 protein in crude leaf extracts can bind to the jasmonate moiety of JA-Ile. Secondly, we employed surface plasmon resonance technology with purified COI1 and JAZ1 protein to reveal the interaction among COI1, JA-Ile and JAZ1. Finally, we utilized the photoaffinity labeling technology to show the direct binding of COR with purified insect-expressed COI1. Taken together, we demonstrate that COI1 functions as a receptor for JA-Ile/COR. In addition, we propose a model to illustrate the molecular interaction between COI1 and jasmonate: JA-Ile binds to COI1 mainly via the keto group of the cyclopentanone ring, the pentenyl side chain and the oxygen atom of the amide group in the jasmonate moiety of JA-Ile.