title: Class V chitin synthase determines pathogenesis in the vascular wilt fungus Fusarium oxysporum and mediates resistance to plant defence compounds.
abstract: Chitin, a beta-1,4-linked polysaccharide of N-acetylglucosamine, is a major structural component of fungal cell walls. Fungi have multiple classes of chitin synthases that catalyse N-acetylglucosamine polymerization. Here, we demonstrate the requirement for a class V chitin synthase during host infection by the vascular wilt pathogen Fusarium oxysporum. The chsV gene was identified in an insertional mutagenesis screen for pathogenicity mutants. ChsV has a putative myosin motor and a chitin synthase domain characteristic of class V chitin synthases. The chsV insertional mutant and a gene replacement mutant of F. oxysporum display morphological abnormalities such as hyphal swellings that are indicative of alterations in cell wall structure and can be partially restored by osmotic stabilizer. The mutants are unable to infect and colonize tomato plants or to grow invasively on tomato fruit tissue. They are also hypersensitive to plant antimicrobial defence compounds such as the tomato phytoanticipin alpha-tomatine or H2O2. Reintroduction of a functional chsV copy into the mutant restored the growth phenotype of the wild-type strain. These data suggest that F. oxysporum requires a specific class V chitin synthase for pathogenesis, most probably to protect itself against plant defence mechanisms.
authors.affiliation: Departamento de Genética, Universidad de Córdoba, Campus Rabanales C5, 14071 Córdoba, Spain.
authors.forename: Martan P
authors.initials: MP
authors.lastname: Madrid
authors.forename: Antonio
authors.initials: A
authors.lastname: Di Pietro
authors.forename: M Isabel G
authors.initials: MI
authors.lastname: Roncero
mesh_terms: D002687:Chitin Synthase / Q000378:metabolism*; D004352:Drug Resistance, Microbial; D005670:Fusarium / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D015966:Gene Expression Regulation, Fungal; D006026:Glycoside Hydrolases; D018551:Solanum lycopersicum / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D010935:Plant Diseases / Q000382:microbiology; D018517:Plant Roots / Q000382:microbiology*; D014774:Virulence / Q000235:genetics
chemical_list: D002687:Chitin Synthase; D006026:Glycoside Hydrolases; C099475:tomatinase