A highly conserved bacterial effector localizes to the host plasma membrane and downregulates the expression of the NDR/HIN1-like 13 (NHL13) gene requiried for antibacterial immunity in Arabidopsis

Many bacterial pathogens of plants and humans cause infections by delivering effector proteins into host cells. Elucidation of how pathogen effector proteins function not only is critical for understanding bacterial pathogenesis, but also provides an important tool in discovering the functions of host genes. In this study, we characterized the Pseudomonas syringae pv. tomato DC3000 effector AvrE, the founding member of a widely distributed, yet functionally enigmatic, bacterial effector family. We show that AvrE is localized in the plasma membrane (PM) and PM-associated vesicle-like structures in the plant cell. AvrE contains two physically interacting domains, and the N terminal portion contains a plasma membrane localization signal. Genome-wide microarray analysis indicates that AvrE, as well as a functionally-redundant effector HopM1, down-regulates the expression of the NDR1/HIN1-Like 13 gene in Arabidopsis. Mutational analysis shows that NHL13 is required for plant immunity, as the nhl13 mutant plant displayed enhanced disease susceptibility. Our results defined the site of action of one of the most important bacterial virulence proteins in plants and the anti-bacterial immunity function of the NHL13 gene.

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Xin XF, Nomura K, Ding X, Chen X, Wang K, Aung K, Uribe F, Rosa B, Yao J, Chen J, He SY