Ectomycorrhizal fungi (EMF) represent one of the major guilds of symbiotic fungi associated with roots of forest trees, where they function to improve plant nutrition and fitness in exchange for plant carbon. Many groups of EMF exhibit preference or specificity for different plant host genera; a good example is the genus Suillus , which grows in association with the conifer family Pinaceae. We investigated genetics of EMF host-specificity by cross-inoculating basidiospores of five species of Suillus onto ten species of Pinus , and screened them for their ability to form ectomycorrhizae. Several Suillus spp. including S . granulatus , S . spraguei , and S . americanus readily formed ectomycorrhizae (compatible reaction) with white pine hosts (subgenus Strobus ), but were incompatible with other pine hosts (subgenus Pinus) . Metatranscriptomic analysis of inoculated roots reveals that plant and fungus each express unique gene sets during incompatible vs. compatible pairings. The Suillus-Pinus metatranscriptomes utilize highly conserved gene regulatory pathways, including fungal G-protein signaling, secretory pathways, leucine-rich repeat and pathogen resistance proteins that are similar to those associated with host-pathogen interactions in other plant-fungal systems. Metatranscriptomic study of the combined Suillus-Pinus transcriptome has provided new insight into mechanisms of adaptation and coevolution of forest trees with their microbial community, and revealed that genetic regulation of ectomycorrhizal symbiosis utilizes universal gene regulatory pathways used by other types of fungal-plant interactions including pathogenic fungal-host interactions. Author Summary Ectomycorrhizal fungi (EMF) comprise the dominant group of symbiotic fungi associated with plant roots in temperate and boreal forests. We examined host-specificity and gene-expression of five EMF Suillus species that exhibited strong patterns of mycorrhizal compatibility/incompatibility with either white pines ( Pinus subg. Strobus ) or hard pines (subg. Pinus ). Using RNA-Seq, we identified conserved transcriptomic responses associated with compatible versus incompatible Pinus – Suillus species pairings. Comparative metatranscriptomic analysis of compatible vs. incompatible pairings allowed us to identify unique sets of fungal and plant genes associated with symbiont recognition and specificity. Comparativ transcriptomic study of the Suillus – Pinus system provides insight into the core functions involved in ectomycorrhizal symbiosis, and the mechanisms by which host-symbiont pairs recognize one another.
【초록키워드】 Transcriptome, Genetic, genetics, Protein, specificity, RNA-Seq, pathogen, response, fitness, adaptation, plant, group, fungi, fungus, host-pathogen interaction, microbial community, interactions, mechanism, fungal, function, association, Signaling, Interaction, Analysis, host-pathogen interactions, Pathways, genetic regulation, plant roots, Comparative, Regulation, exchange, genus, pathogenic, Express, pine, carbon, leucine, coevolution, regulatory pathways, gene-expression, Metatranscriptomic analysis, symbiont, regulatory pathway, dominant, Host, transcriptomic, FIVE, IMPROVE, identify, examined, conserved, example, involved, inoculated, investigated, provided, screened, exhibited, provide, unique, recognize, reveal, G-protein, incompatible, Pinaceae, 【제목키워드】 pattern, common,