title: Comparative analysis of transcript abundance in Pinus sylvestris after challenge with a saprotrophic, pathogenic or mutualistic fungus.
abstract: To investigate functional differences in the recognition and response mechanisms of conifer roots to fungi with different trophic strategies, Pinus sylvestris L. was challenged with a saprotrophic fungus Trichoderma aureoviride Rifai. The results were compared with separate studies investigating pine interactions with a pathogen, Heterobasidion annosum (Fr.) Bref. sensu stricto and an ectomycorrhizal symbiont, Laccaria bicolor Maire (Orton). Global changes in the expression of 2109 conifer genes were assayed 1, 5 and 15 days after inoculation. Gene expression data from a cDNA microarray were analyzed by the 2-interconnected mixed linear model statistical approach. The total number of genes differentially expressed compared with the uninfected control was similar after challenge with the pathogen and the ectomycorrhizal symbiont, but the number of differentially expressed genes increased over time for H. annosum, and decreased for L. bicolor. Inoculation of pine roots with T. aureoviride resulted overall in a much lower number of genes with changed transcript levels compared with inoculation with H. annosum or L. bicolor. Functional classification of the differentially expressed genes revealed that the ectomycorrhizal fungus triggered transient induction of defence-related genes. The response and induction of defence against the pathogen was delayed and the magnitude increased over time. Thus, there were specific transcriptional responses depending on whether the conifer roots were challenged with mutualistic, saprotrophic or pathogenic fungi. This suggests that pine trees are able to recognize diverse fungal species and specifically distinguish whether they are pathogenic, neutral or beneficial microbial agents.
authors.affiliation: Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, P.O. Box 7026, Uppsala, Sweden.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Adomas
authors.forename: Gregory
authors.initials: G
authors.lastname: Heller
authors.forename: Ake
authors.initials: A
authors.lastname: Olson
authors.forename: Jason
authors.initials: J
authors.lastname: Osborne
authors.forename: Magnus
authors.initials: M
authors.lastname: Karlsson
authors.forename: Jarmila
authors.initials: J
authors.lastname: Nahalkova
authors.forename: Len
authors.initials: L
authors.lastname: Van Zyl
authors.forename: Ron
authors.initials: R
authors.lastname: Sederoff
authors.forename: Jan
authors.initials: J
authors.lastname: Stenlid
authors.forename: Roger
authors.initials: R
authors.lastname: Finlay
authors.forename: Frederick O
authors.initials: FO
authors.lastname: Asiegbu
mesh_terms: D001487:Basidiomycota / Q000472:pathogenicity*; D002450:Cell Communication; D008855:Microscopy, Electron, Scanning; D041605:Pinus sylvestris / Q000235:genetics* / Q000382:microbiology* / Q000502:physiology; D010935:Plant Diseases / Q000382:microbiology*; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000382:microbiology / Q000648:ultrastructure; D012269:Ribosomal Proteins / Q000096:biosynthesis / Q000378:metabolism; D036226:Seedlings / Q000382:microbiology*; D014158:Transcription, Genetic; D014242:Trichoderma / Q000472:pathogenicity* / Q000648:ultrastructure
chemical_list: D010940:Plant Proteins; D012269:Ribosomal Proteins