A proteomic investigation of Phytophthora species using mass spectrometry and reverse genetics

Organisms in the genus Phytophthora are important plant pathogens, although understudied. Phytophthora was first brought into human awareness with the identification of P. infestans as the culprit for the Irish potato famine in the mid 1800s. Since then, over 80 Phytophthora species have been identified, many of which infect a wide variety of crops worldwide with devastating results.

Traditionally, much of the work aimed at controlling Phytophthora diseases involved applied research. In recent years there has been a marked increase in molecular work on Phytophthora. This increase is evident not only from increased funding by agencies such as the National Science Foundation (NSF), but also from the type of research applied to Phytophthora for the first time. The first Phytophthora species to have their genomes sequenced were P. sojae and P. ramorum at 2004. Since then the genomes of two more Phytophthora species- P. capsici and P. infestans, were also sequenced.

Availability of Phytophthora genome sequences provided us with the basis necessary for a proteomic investigation of these organisms. The study presented here represents the first large scale proteomic study of any Phytophthora species. Using mass spectrometry and available or newly developed bioinformatic tools we measured the proteomes of different asexual Phytophthora life stages. We also measured the protein complement of P. capsici infected tomato plants, the so called “interactome”, in order to gain an insight into the biological processes occurring in the pathogen during infection, and in the plant in response to the pathogen. We also used data from these proteomic experiments as a part of a novel approach aimed at improving the genome annotation of those Phytophthora species. Finally, we used different molecular techniques, including a reverse genetic technique called Targeted Induced Local Lesions in Genome (TILLING), to begin characterization of a few protein targets identified in those experiments.

The accumulated data from all our experiments identified certain molecular processes, metabolic and others, that may explain the success of Phytophthora as a plant pathogen. The data from these experiments provides a platform on which future experiments can be based on to further characterize these interesting organisms.