title: SnTox3 acts in effector triggered susceptibility to induce disease on wheat carrying the Snn3 gene.
abstract: The necrotrophic fungus Stagonospora nodorum produces multiple proteinaceous host-selective toxins (HSTs) which act in effector triggered susceptibility. Here, we report the molecular cloning and functional characterization of the SnTox3-encoding gene, designated SnTox3, as well as the initial characterization of the SnTox3 protein. SnTox3 is a 693 bp intron-free gene with little obvious homology to other known genes. The predicted immature SnTox3 protein is 25.8 kDa in size. A 20 amino acid signal sequence as well as a possible pro sequence are predicted. Six cysteine residues are predicted to form disulfide bonds and are shown to be important for SnTox3 activity. Using heterologous expression in Pichia pastoris and transformation into an avirulent S. nodorum isolate, we show that SnTox3 encodes the SnTox3 protein and that SnTox3 interacts with the wheat susceptibility gene Snn3. In addition, the avirulent S. nodorum isolate transformed with SnTox3 was virulent on host lines expressing the Snn3 gene. SnTox3-disrupted mutants were deficient in the production of SnTox3 and avirulent on the Snn3 differential wheat line BG220. An analysis of genetic diversity revealed that SnTox3 is present in 60.1% of a worldwide collection of 923 isolates and occurs as eleven nucleotide haplotypes resulting in four amino acid haplotypes. The cloning of SnTox3 provides a fundamental tool for the investigation of the S. nodorum-wheat interaction, as well as vital information for the general characterization of necrotroph-plant interactions.
authors.affiliation: Department of Plant Pathology, North Dakota State University, Fargo, North Dakota, United States of America.
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Liu
authors.forename: Justin D
authors.initials: JD
authors.lastname: Faris
authors.forename: Richard P
authors.initials: RP
authors.lastname: Oliver
authors.forename: Kar-Chun
authors.initials: KC
authors.lastname: Tan
authors.forename: Peter S
authors.initials: PS
authors.lastname: Solomon
authors.forename: Megan C
authors.initials: MC
authors.lastname: McDonald
authors.forename: Bruce A
authors.initials: BA
authors.lastname: McDonald
authors.forename: Alberto
authors.initials: A
authors.lastname: Nunez
authors.forename: Shunwen
authors.initials: S
authors.lastname: Lu
authors.forename: Jack B
authors.initials: JB
authors.lastname: Rasmussen
authors.forename: Timothy L
authors.initials: TL
authors.lastname: Friesen
mesh_terms: D000595:Amino Acid Sequence; D001203:Ascomycota / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D015139:Blotting, Southern; D004229:Dithiothreitol; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015966:Gene Expression Regulation, Fungal; D014644:Genetic Variation; D054884:Host-Pathogen Interactions / Q000235:genetics; D008969:Molecular Sequence Data; D009183:Mycotoxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010843:Pichia / Q000235:genetics / Q000378:metabolism; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014908:Triticum / Q000235:genetics* / Q000382:microbiology; D014774:Virulence
chemical_list: D005656:Fungal Proteins; D009183:Mycotoxins; D011994:Recombinant Proteins; D004229:Dithiothreitol