Defense-Suppressive Fragments of RIN4 generated by AvrRpt2 Participate in NDR1-dependent Activation of RPS2

Abstract Plant nucleotide-binding, leucine-rich-repeat (NLR) immune receptors recognize pathogen effectors and activate immunity. The NLR RPS2 recognizes AvrRpt2, a Pseudomonas effector that promotes virulence by proteolytically cleaving a membrane-tethered host protein, RIN4. RIN4 cleavage by AvrRpt2 generates fragments that activate RPS2. A model for RPS2 activation by RIN4 destruction is consistent with the ectopic activity of RPS2 in plants lacking RIN4 but does not explain the link between AvrRpt2’s virulence activity and RPS2 activation. We found that non-membrane-tethered RIN4 derivatives are potent cytosolic activators of RPS2. Activation of RPS2 by these RIN4 derivatives, like AvrRpt2-induced activation, and unlike ectopic activation in the absence of RIN4, requires the defense signaling protein NDR1. Cleavage products of RIN4 produced by AvrRpt2 play contrasting roles in the activation of RPS2, with the membrane-tethered C-terminal fragment suppressing RPS2 and the non-membrane-tethered internal fragment, dependent on compatibility with the C-terminal fragment, overcoming its suppression of RPS2. Highlights Non-membrane tethered derivatives of RIN4 activate RPS2-induced cell death Activation of RPS2 by non-membrane-tethered derivatives of RIN4 requires NDR1 AvrRpt2-induced cleavage fragments of RIN4 play contrasting roles in RPS2 activation Competing Interest Statement The authors have declared no competing interest. Footnotes ↵12 Lead contact This version of the manuscript has been revised to update the following figures: Figure 1, 2, 3 and 5 and Supplemental figure 1, 3 and 5. Additionally the graphical abstract has been removed- please refer to figure 10.