Identification of an SCF ubiquitin-ligase complex required for auxin response in Arabidopsis thaliana

The plant hormone auxin regulates diverse aspects of plant growth and devel opment. We report that in Arabidopsis, auxin response is dependent on a ubi quitin-ligase (E3) complex called SCFTIR1. The complex consists of proteins related to yeast Skp1p and Cdc53p called ASK and AtCUL1, respectively, as well as the F-box protein TIR1, Mutations ia either ASK1 or TIR1 result in decreased aurin response. Further, overexpression of TIR1 promotes auxin re sponse suggesting that SCFTIR1 is limiting for the response. These results provide new support for a model in which auxin action depends on the regula ted proteolysis of repressor proteins.