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Gene Expression Profiling During Asexual Development of the Late Blight Pathogen Phytophthora infestans Reveals a Highly Dynamic Transcriptome

¹Department of Plant Pathology and Microbiology, University of California, Riverside 92521, U.S.A.; ²Syngenta Biotechnology, Research Triangle Park, NC 27709, U.S.A.; ³Plant Pathology Programme, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, U.K.; ⁴College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, U.K.; ⁵Department of Plant Pathology, The Ohio State University, Wooster 44691, U.S.A.; ⁶Laboratory of Phytopathology, Wageningen University, NL-6709 PD Wageningen, The Netherlands; ⁷Syngenta Limited, Jealott's Hill International Research Station, Bracknell, Berks RG42 6EY, U.K.

Much of the pathogenic success of Phytophthora infestans, the potato and tomato late blight agent, relies on its ability to generate from mycelia large amounts of sporangia, which release zoospores that encyst and form infection structures. To better understand these stages, Affymetrix GeneChips based on 15,650 unigenes were designed and used to profile the life cycle. Approximately half of P. infestans genes were found to exhibit significant differential expression between developmental transitions, with approximately ¹/₁₀ being stage-specific and most changes occurring during zoosporogenesis. Quantitative reverse-transcription polymerase chain reaction assays confirmed the robustness of the array results and showed that similar patterns of differential expression were obtained regardless of whether hyphae were from laboratory media or infected tomato. Differentially expressed genes encode potential cellular regulators, especially protein kinases; metabolic enzymes such as those involved in glycolysis, gluconeogenesis, or the biosynthesis of amino acids or lipids; regulators of DNA synthesis; structural proteins, including predicted flagellar proteins; and pathogenicity factors, including cell-wall-degrading enzymes, RXLR effector proteins, and enzymes protecting against plant defense responses. Curiously, some stage-specific transcripts do not appear to encode functional proteins. These findings reveal many new aspects of oomycete biology, as well as potential targets for crop protection chemicals.

Additional keywords:appressorium, microarray, sporulation.