Dynamic Perception of Jasmonates by the F-Box Protein COI1.

Jasmonates (JAs) are cyclic fatty acid-derived phytohormones that regulate diverse aspects of plant defense and development. The endogenous active JA molecule (+)-7-iso-JA-L -Ile (JA-Ile) and its analog coronatine trigger formation of a complex with the F-box protein COI1 and JAZ repressors to induce degradation of the JAZs through the 26S proteasome pathway in a COI1-dependent manner. To reveal the formation process of COI1-JA-JAZ ternary complex, we employed several biochemical approaches to examine how JA is dynamically perceived. These analyses showed that the COI1 proteins of Arabidopsis and rice bind JA with appreciable binding affinity and revealed the kinetics and thermodynamics of the COI1-JA-JAZ ternary complex. Our results suggest that COI1 is the primary receptor perceiving the active JA molecule to initially form a COI1-JA complex that subsequently recruits JAZs for further signal transduction.