Plant, Animal & Microbe Genomes X Conference

January 12-16, 2002
Town & Country Convention Center
San Diego, CA

Poster: Functional Genomics for Microorganisms
          

FROM SEQUENCE TO FUNCTION: NOVEL EXTRACELLULAR SIGNAL PROTEINS FROM Phytophthora infestans

¹ DEPARTMENT OF PLANT PATHOLOGY, THE OHIO STATE UNIVERSITY-OARDC, WOOSTER, OH 44691

Interactions between plants and microbial pathogens involve complex signal exchanges at the plant surface and intercellular space interface. Surface components of a pathogen must play important roles in the development of a complete infection cycle and recognition by resistant plants. We aim at identifying extracellular proteins from Phytophthora infestans, an economically important oomycete pathogen. Targeting extracellular proteins will increase the probability of identifying proteins essential for virulence and avirulence of the pathogen. We developed and validated an algorithm (PexFinder V1.0) for automated identification of secreted and membrane proteins from expressed sequence tag (EST) data sets. Analysis of 2,147 ESTs from P. infestans using PexFinder identified 261 ESTs (12.2%) corresponding to a set of 142 nonredundant Pex (Phytophthora extracellular proteins) genes. Of these, 78 (55%) Pex cDNAs are novel with no significant matches in public databases. Functional genetic assays, such as high throughput virus and Agrobacterium-based expression systems were applied to the novel Pex genes to determine their role in virulence/avirulence. This led to the discovery of two novel necrosis-inducing cDNAs crn1 and crn2, encoding putative extracellular proteins with no similarity to sequences in public databases. However, TBLASTN searches against recent Phytophthora EST databases revealed at least 21 different members in three Phytophthora species. Phylogenetic analysis of this large gene family will also be presented.