title: The glyoxylate cycle is involved in pleotropic phenotypes, antagonism and induction of plant defence responses in the fungal biocontrol agent Trichoderma atroviride.
abstract: Isocitrate lyase (ICL), a signature enzyme of the glyoxylate cycle, is required for metabolism of non-fermentable carbon compounds like acetate or ethanol, and virulence in bacteria and fungi. In the present study, we investigate the role of the glyoxylate cycle in the fungal biocontrol agent Trichoderma atroviride by generating icl deletion and complementation mutants. Phenotypic analyses of the deletion mutant Δicl suggest that ICL is required for normal growth, conidial pigmentation and germination, and abiotic stress tolerance. The Δicl strain display reduced antagonism towards Botrytis cinerea in plate confrontation assays. Secretion and sandwich assays further show that secreted factors are partly responsible for the reduced antagonism. Furthermore, in vitro root colonization assays shows that the Δicl strain retains the ability to internally colonize Arabidopsis thaliana roots. However, the Δicl strain has a reduced ability to induce systemic defence in A. thaliana leaves that results in reduced protection against B. cinerea. These data shows that ICL and the glyoxylate cycle are important for biocontrol traits in T. atroviride, including direct antagonism and induction of defence responses in plants.
authors.affiliation: Uppsala BioCenter, Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Box 7026, 75007 Uppsala, Sweden. Electronic address: mukesh.dubey@slu.se.
authors.forename: Mukesh K
authors.initials: MK
authors.lastname: Dubey
authors.forename: Anders
authors.initials: A
authors.lastname: Broberg
authors.forename: Sanjeewani
authors.initials: S
authors.lastname: Sooriyaarachchi
authors.forename: Wimal
authors.initials: W
authors.lastname: Ubhayasekera
authors.forename: Dan Funck
authors.initials: DF
authors.lastname: Jensen
authors.forename: Magnus
authors.initials: M
authors.lastname: Karlsson
mesh_terms: D000898:Antibiosis; D017360:Arabidopsis / Q000276:immunology* / Q000382:microbiology; D020171:Botrytis / Q000502:physiology; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D006038:Glyoxylates / Q000378:metabolism*; D007522:Isocitrate Lyase / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology*; D014242:Trichoderma / Q000201:enzymology / Q000235:genetics / Q000502:physiology*
chemical_list: D005656:Fungal Proteins; D006038:Glyoxylates; D007522:Isocitrate Lyase; C031150:glyoxylic acid
keywords: Antagonism; Biocontrol; Glyoxylate cycle; Isocitrate lyase; Trichoderma atroviride