Biosciences Department Seminar
"Conserved Effector Proteins from Oomycete Phytopathogens Suppress Immune Responses in Plants"
Presented by Devdutta Deb, B.S., M.S., Virginia Polytechnic Institute and State University
Friday, May 17, 2013, 11 am
John Dunn Seminar Room, Bldg. 463
Hosted by: Benjamin Babst, Ph.D., Biosciences Dept.
Effector proteins are exported to the interior of host cells by numerous plant pathogens. Effector proteins have been well characterized in bacteria. Contrastingly, the mechanisms through which these effectors promote virulence are largely unknown. Bioinformatic analysis of genome sequences from oomycete pathogens Phytophthora sojae, P. ramorum, P. infestans and Hyaloperonospora arabidopsidis (Hpa) have led to the identification of a large number of candidate effector genes. These effector genes have characteristic motifs (signal peptide, RxLR and dEER) that target the effectors into plant cells. Although these effector genes are very diverse, certain genes are conserved between P. sojae and H. arabidopsidis, suggesting that they play important roles in pathogenicity. The goal of my first project was to characterize a pair of conserved effector candidates from Hpa and P.sojae. We hypothesized that these effectors have important conserved roles with regard to infection. We found that the Hpa effector was expressed early during the course of infection of Arabidopsis and triggered an ecotype-specific defense response in Arabidopsis, suggesting that it was recognized by host surveillance proteins. Both the effectors from Hpa and P. sojae respectively could suppress immunity triggered by pathogen associated molecular patterns (PTI) and by effectors (ETI) in planta. They also enhanced bacterial virulence in Arabidopsis when delivered by the Type III secretion system. Similar results were seen with experiments with transgenic Arabidopsis expressing the effectors.