Phytophthora effectors promote infection by suppressing small RNA silencing in plants
W. MA (1), Y. Zhai (1), D. Choi (1), Y. Hou (1), T. Kuan (1), J. He (2), J. Ma (2) (1) University of California, U.S.A.; (2) Fudan University, China

Filamentous eukaryotic pathogens including fungi and oomycetes are major threats of plant health. During the co-evolutionary arms race with the host, these pathogens evolved a large number of secreted virulence proteins, called effectors, to facilitate colonization and infection. A fundamental function of effectors is to dampen immunity through direct manipulation of targeted processes inside the host cells. Recently, we discovered that the destructive Phytophthora pathogens encode RNA silencing suppressors. These effectors promote infection, likely through their interference with host small RNA-mediated defense. Our on-going research aims to understand the virulence mechanism of Phytophthora Suppressor of RNA silencing 2 (PSR2). In plants, PSR2 associates with double-stranded RNA-binding proteins and specifically affects the accumulation of secondary small interfering RNAs (siRNAs). Genetic characterizations of Arabidopsis mutants defective in the biogenesis of secondary siRNAs support their role in plant defense during Phytophthora infection. Furthermore, PSR2 belongs to an evolutionarily conserved RxLR effector family containing the characteristic L-W-Y motif repeats. Crystal structure of PSR2 shows that each L-W-Y module folds into a five-helix bundle. The biological significance of this architecture will be discussed.


Abstract Number: C17-2
Session Type: Concurrent