Abstract
We have previously shown that OsRac1, a small GTPase in rice, is involved in defense responses. We isolated OsRac1-interacting proteins and showed signaling network with OsRac1. Now, we analyzed whether the OsRac1 complex is composed and how it behaves. Cell cultures expressing constitutively active form of OsRac1 (CA-OsRac1) or dominant negative form of OsRac1 (DN-OsRac1) fractionated by gel filtration were analyzed. The CA-OsRac1 complex formed a higher molecular weight complex than DN-OsRac1 complex. Next, elicitor-treated cell cultures expressing wild type form of OsRac1 were analyzed. Results indicate that the OsRac1 complex forms a larger complex at 10 minutes after elicitor treatment, and the complex is dissociated at 20 minutes. Defensome components in fractions of high molecular weight complex were not altered by elicitor treatment. And we show OsRac1 is activated by elicitor treatment. These results suggest that components of the OsRac1 complex except for OsRac1 form a protein complex first, and when defense signaling is triggered by elicitors, OsRac1 forms a larger complex. After signaling is terminated, OsRac1 is likely to be dissociated from the preformed complex.
