Abstract
Pathogens generate and secrete effector proteins to the host plant cells during pathogenesis to promote virulence and colonization.If the plant carries resist-ance(R)proteins that recognize pathogen effectors,effector-triggered immunity(ETI)is activated,re-sulting in a robust immune response and hyper-sensitive response(HR).The bipartite effector AvrRps4 from Pseudomonas syringae pv.pisi has been well studied in terms of avirulence function.In planta,AvrRps4 is processed into two parts.The C-terminal fragment of AvrRps4(AvrRps4C)induces HR in tumip and is recognized by the paired resistance proteins AtRRS1/AtRPS4 in Arabidopsis.Here,we show that AvrRps4C targets a group of Arabidopsis WRKY,including WRKY46,WRKY53,WRKY54,and WRKY70,to induce its virulence function.Indeed,AvrRps4C suppresses the general binding and tran-scriptional activities of immune-positive regulator WRKY54 and WRKY54-mediated resistance.AvrRps4C interferes with WRKY54's binding activity to target gene SARD1 in vitro,suggesting WRKY54 is sequestered from the SARD1 promoter by AvrRps4C.Through the interaction of AvrRps4C with four WRKYs,AvrRps4 enhances the formation of homo-/heterotypic complexes of four WRKYs and seques-ters them in the cytoplasm,thus inhibiting their function in plant immunity.Together,our results provide a detailed virulence mechanism of AvrRps4 through its C-terminus.
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