title: A Kazal-like extracellular serine protease inhibitor from Phytophthora infestans targets the tomato pathogenesis-related protease P69B.
abstract: The oomycetes form one of several lineages within the eukaryotes that independently evolved a parasitic lifestyle and consequently are thought to have developed alternative mechanisms of pathogenicity. The oomycete Phytophthora infestans causes late blight, a ravaging disease of potato and tomato. Little is known about processes associated with P. infestans pathogenesis, particularly the suppression of host defense responses. We describe and functionally characterize an extracellular protease inhibitor, EPI1, from P. infestans. EPI1 contains two domains with significant similarity to the Kazal family of serine protease inhibitors. Database searches suggested that Kazal-like proteins are mainly restricted to animals and apicomplexan parasites but appear to be widespread and diverse in the oomycetes. Recombinant EPI1 specifically inhibited subtilisin A among major serine proteases and inhibited and interacted with the pathogenesis-related P69B subtilisin-like serine protease of tomato in intercellular fluids. The epi1 and P69B genes were coordinately expressed and up-regulated during infection of tomato by P. infestans. Inhibition of tomato proteases by EPI1 could form a novel type of defense-counterdefense mechanism between plants and microbial pathogens. In addition, this study points to a common virulence strategy between the oomycete plant pathogen P. infestans and several mammalian parasites, such as the apicomplexan Toxoplasma gondii.
authors.affiliation: Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, Ohio 44691, USA.
authors.forename: Miaoying
authors.initials: M
authors.lastname: Tian
authors.forename: Edgar
authors.initials: E
authors.lastname: Huitema
authors.forename: Luis
authors.initials: L
authors.lastname: Da Cunha
authors.forename: Trudy
authors.initials: T
authors.lastname: Torto-Alalibo
authors.forename: Sophien
authors.initials: S
authors.lastname: Kamoun
mesh_terms: D000595:Amino Acid Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D019992:Databases as Topic; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D018551:Solanum lycopersicum / Q000382:microbiology*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010838:Phytophthora / Q000201:enzymology*; D010935:Plant Diseases / Q000382:microbiology; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012697:Serine Endopeptidases / Q000737:chemistry; D015842:Serine Proteinase Inhibitors / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D013381:Subtilisins / Q000737:chemistry; D013997:Time Factors; D014359:Trypsin Inhibitor, Kazal Pancreatic / Q000737:chemistry; D015854:Up-Regulation; D014774:Virulence
chemical_list: D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; D014359:Trypsin Inhibitor, Kazal Pancreatic; D012313:RNA; D010450:Endopeptidases; D012697:Serine Endopeptidases; D013381:Subtilisins