title: Role of gliotoxin in the symbiotic and pathogenic interactions of Trichoderma virens.
abstract: Using a gene disruption strategy, we generated mutants in the gliP locus of the plant-beneficial fungus Trichoderma virens that were no longer capable of producing gliotoxin. Phenotypic assays demonstrated that the gliP-disrupted mutants grew faster, were more sensitive to oxidative stress and exhibited a sparse colony edge compared with the WT strain. In a plate confrontation assay, the mutants deficient in gliotoxin production were ineffective as mycoparasites against the oomycete, Pythium ultimum, and the necrotrophic fungal pathogen, Sclerotinia sclerotiorum, but retained mycoparasitic ability against Rhizoctonia solani. Biocontrol assays in soil showed that the mutants were incapable of protecting cotton seedlings from attack by P. ultimum, against which the WT strain was highly effective. The mutants, however, were as effective as the WT strain in protecting cotton seedlings against R. solani. Loss of gliotoxin production also resulted in a reduced ability of the mutants to attack the sclerotia of S. sclerotiorum compared with the WT. The addition of exogenous gliotoxin to the sclerotia colonized by the mutants partially restored their degradative abilities. Interestingly, as in Aspergillus fumigatus, an opportunistic human pathogen, gliotoxin was found to be involved in pathogenicity of T. virens against larvae of the wax moth, Galleria mellonella. The loss of gliotoxin production in T. virens was restored by complementation with the gliP gene from A. fumigatus. We have, thus, demonstrated that the putative gliP cluster of T. virens is responsible for the biosynthesis of gliotoxin, and gliotoxin is involved in mycoparasitism and biocontrol properties of this plant-beneficial fungus.
authors.affiliation: Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Suipacha 531, Rosario 2000, Argentina.
authors.forename: Walter A
authors.initials: WA
authors.lastname: Vargas
authors.affiliation: Nuclear Agriculture and Biotechnology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India.
authors.forename: Prasun K
authors.initials: PK
authors.lastname: Mukherjee
authors.affiliation: Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843-2132, USA.
authors.forename: David
authors.initials: D
authors.lastname: Laughlin
authors.affiliation: Fungal Genetics Stock Center, University of Missouri-Kansas City, Kansas City, MO 64110, USA.
authors.forename: Aric
authors.initials: A
authors.lastname: Wiest
authors.affiliation: Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843-2132, USA.
authors.forename: Maria E
authors.initials: ME
authors.lastname: Moran-Diez
authors.affiliation: Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843-2132, USA.
authors.forename: Charles M
authors.initials: CM
authors.lastname: Kenerley
mesh_terms: D000818:Animals; D001203:Ascomycota / Q000254:growth & development; D005912:Gliotoxin / Q000378:metabolism*; D003368:Gossypium / Q000382:microbiology*; D007915:Lepidoptera / Q000382:microbiology; D056265:Microbial Interactions; D016254:Mutagenesis, Insertional; D018384:Oxidative Stress; D010572:Pest Control, Biological; D010935:Plant Diseases / Q000382:microbiology*; D011775:Pythium / Q000254:growth & development; D012232:Rhizoctonia / Q000254:growth & development; D036226:Seedlings / Q000382:microbiology; D012988:Soil Microbiology; D016019:Survival Analysis; D013559:Symbiosis; D014242:Trichoderma / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D014774:Virulence
chemical_list: D005912:Gliotoxin