[BK21 Plus Seminar]

▶Subject: Structural and functional analyses of Phytophthora sojae RxLR effector PSR2 reveal functional domains for host RNA silencing suppression activity

▶Speaker: Du Seok Choi, Ph.D.
(Department of Plant Pathology and Microbiology, University of California Riverside)

▶Date: 3:30 PM/Dec. 27(Tue.)/2016

▶Place: Conference room(#376), Postech Biotech Center

*Abctract
Small RNA silencing is a universal gene regulation mechanism in eukaryotes. There is an emerging body of evidence suggesting that small RNAs are integral regulators of plant immunity during the infection of filamentous eukaryotic pathogens including fungi and oomycetes. To overcome this defense, the destructive oomycete pathogens in the genus Phytophthora have evolved effector proteins to specifically suppress small RNA silencing. Previously, Phytophthora suppressor of RNA silencing 2 (PSR2) of Phytophthora sojae was identified as an important virulence factor. Here, we report the motif arrangement and crystal structure of PSR2. PSR2 is an RxLR effector containing multiple L-W-Y motif modules that form tandem repeats. Structural analysis shows that each L-W-Y module folds into a five-helix bundle that is stabilized by a hydrophobic core. The overall structure looks like a string of helix-bundles linked by loops. Using mutagenesis analysis, we found that the first three repeats and the C-terminal module are required for RNA silencing suppression activity of PSR2. Furthermore, an N-terminal region between the secretion signal peptide and the first module, although not required for RNA silencing suppression activity, seems to prevent host recognition of PSR2 in N. benthamiana. Effectors containing similar tandem repeats are prevalent in all Phytophthora species, supporting essential biological significance of this architecture.

▶Inquiry: Prof. Sohn, Kee Hoon (279-2357)
* This seminar will be given in English.
please refrain from taking photos during seminars. *