The RhoGAP SPIN6 Associates with SPL11 and OsRac1 and Negatively Regulates Programmed Cell Death and Innate Immunity in XXXX .

@entity3007 @entity958 @entity16990 @entity26 @entity3006 @entity8812 @entity579 @entity71907 @entity204
UNASSIGNED: The ubiquitin proteasome system in plants plays important roles in plant-microbe interactions and in immune responses to pathogens. We previously demonstrated that the @entity579 U-box E3 ligase SPL11 and its @entity958 ortholog @entity71907 negatively regulate @entity204 ( @entity204 ) and defense response. However, the components involved in the SPL11/ @entity71907 -mediated @entity204 and immune signaling pathway remain unknown. In this study, we report that SPL11-interacting Protein 6 (SPIN6) is a Rho GTPase-activating protein (RhoGAP) that interacts with SPL11 in vitro and in vivo. SPL11 ubiquitinates SPIN6 in vitro and degrades SPIN6 in vivo via the 26S proteasome-dependent pathway. Both RNAi silencing in transgenic @entity579 and knockout of Spin6 in a T-DNA insertion mutant lead to @entity204 and increased resistance to the @entity579 blast pathogen @entity8812 and the bacterial blight pathogen @entity16990 . oryzae. The levels of reactive @entity26 species and defense-related gene expression are significantly elevated in both the Spin6 RNAi and mutant plants. Strikingly, SPIN6 interacts with the small GTPase OsRac1, catalyze the @entity3007 -bound OsRac1 into the @entity3006 -bound state in vitro and has GAP activity towards OsRac1 in @entity579 cells. Together, our results demonstrate that the RhoGAP SPIN6 acts as a linkage between a U-box E3 ligase-mediated ubiquitination pathway and a small GTPase-associated defensome system for plant immunity.
