Agricultural Microbes Genome 2 Conference Agricultural Microbes Genome 2 Conference
Poster: Systematic Functional Analysis
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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 survival 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. The program integrates a series of sequence analysis scripts with signal peptide predictions based on SignalP V2.0 (http://www.cbs.dtu.dk/services/SignalP-2.0/). Analysis of 2,147 ESTs from P. infestans using PexFinder identified 261 ESTs (12.2%) corresponding to a set of 145 nonredundant Pex (Phytophthora extracellular proteins) genes. Of these, 85 (59%) Pex genes are novel with no significant matches in public databases. The algorithm was validated using a number of methods. For example, PexFinder identified numerous genes with significant matches to known extracellular proteins, as well as all previously characterized extracellular proteins from Phytophthora that were represented in the EST data set. Functional genetic assays, such as high throughput virus and Agrobacterium-based expression systems, are being applied to the novel Pex genes to determine their role in virulence/avirulence.