Proposed working model of the relationship between SPL11, SPIN6, and OsRac1.

<p>By associating with RhoGAP protein SPIN6, the E3 ligase SPL11 negatively modulates OsRac1-mediated immune signaling. SPIN6 is ubiquitinated and degraded by the E3 ligase SPL11 via the 26S proteasome system. From the GDP state to the GTP state, OsRac1 is activated by the GEF protein OsRacGEF1, then associates with the NADPH oxidases OsRBOH/CDPK complex to trigger ROS generation. The activation of OsRac1 requires the phosphorylation by the kinase protein OsCERK1, a co-receptor of the PAMP effector chitin. OsCERK1 dimerizes with LysM protein CEBiP1 to perceive chitin signaling. The interaction between SPIN6 and OsRac1 may lead to the change of OsRac1 from the GTP state to the GDP state, which reduces the active form of OsRac1 in rice cells. Mutation in the <i>Spin6</i> gene may cause accumulation of ROS and PR proteins, i.e., PR1a, PR5 and PBZ1, that results in plant cell death and immunity.