Regulation Mechanism of Protein Stability of the F-box Protein COI1 from Tomato and Tobacco

Arabidopsis COI1 (coronatine insensitive 1),an F-box protein that physically interacts with ASK1 (Arabidopsis serine/Threonine kinase 1) protein to form SCFCOI1-E3 ligase complex,perceives jasmonate signals and modulates diverse aspects of the jasmonate-regulated plant defense and developmental processes.The COIl homologs from various plant species have recently been identified,however,little is known about the molecular mechanism regulating protein stability of these COI1 homologs.In this study,we demonstrated that the COI1 homologs from vegetable crop Solanum lycopersicum and commercial plant Nicotiana attenuata remain stable via interacting with ASK1 protein,suggesting that assembly of SCFCOI1 complexes contributes to the stabilization of COI1 homologs.Meanwhile,the 26S proteasome inhibitor represses the degradation of COI1 homologs,demonstrating that ubiquitin-proteasome pathway plays a role in degradation of the COI1 homologs.These results suggest that two antagonistic pathways work together to maintain COI1 protein in tomato and tobacco at a suitable abundance for proper biological function.