The bacterial Type III-secreted protein AvrRps4 is a bipartite effector   
W. GASSMANN (1), M. Halane (2), S. Kim (2), C. Garner (2), S. Bhattacharjee (2) (1) University of Missouri, U.S.A.; (2) University of Missouri, U.S.A.

The resistance protein RPS4 functions as a pair with RRS1 to trigger resistance to bacterial AvrRps4, which is processed in planta after Gly133. Based on heterologous transient overexpression studies it was suggested that the C-terminal AvrRps4 fragment (AvrRps4-C, amino acids 134-221) alone is sufficient to trigger resistance, but evidence with natural levels of AvrRps4 is lacking. We fused the AvrRpm1 secretion signal peptide to AvrRps4-C (SP-AvrRps4-C) or to full-length AvrRps4 as a control using the vector pVSP_PsSPdes [1]. With a series of experiments, we discovered that 1) the AvrRpm1-SP mislocalizes fused AvrRps4 to membranes, 2) this may not be noticed with SP-AvrRps4 because of processing and a contribution to resistance by HopK1, an endogenous DC3000 effector whose N-terminus is 75% identical to AvrRps4-N, is processed at Gly133, and can replace AvrRps4-N in a HopK1-N:AvrRps4-C chimera, 3) avirulence activity of SP-AvrRps4 is abolished when this construct is delivered by DC3000(hopK1-), even though processing and liberation of AvrRps4-C still occurs, and 4) AvrRps4-triggered immunity is reconstituted if AvrRps4-N is provided with SP-AvrRps4 from a separate plasmid in DC3000(hopK1-). In summary, we show that both untethered AvrRps4-N (or HopK1-N) and AvrRps4-C need to be present in the plant cell for resistance to occur. Additional data and implications of our findings for current models of AvrRps4 recognition will be discussed.

Abstract Number: P17-528
Session Type: Poster