Analysis of OsRac1 protein complex involved in defense signaling of rice

Abstract

We have previously shown that OsRac1, a small GTPase Rac of rice, is involved in defense responses. In this study, we found that OsRac1 associates with OsRAR1, an important component of R gene mediated disease resistance, in one complex and the membrane localization might be required for this association. The heat shock proteins 90 and 70, the molecular chaperones, were also found in the OsRac1 complex. Suppression of RAR1 or treatment of the Hsp90 specific inhibitor, geldanamycin, strongly suppressed PR gene expression induced by SE in the CA-OsRac1 cultured cells. These results suggest the involvement of the Hsp90 and OsRAR1 in OsRac1 related defense signaling pathway. OsMAPK6, a novel rice MAPK homologous to tobacco NtSIPK and Arabidopsis AtMAPK6 involved in cell death and disease resistance, was also detected in the CA-OsRac1 complex. Together, our results suggest a key role of OsRac1 in the early steps of defense signaling.