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Tricholoma matsutake and its related species are ectomycorrhizal Agaricomycetes that produce prized mushrooms collectively called 'matsutake'. These mushrooms are mainly distributed in the Northern Hemisphere. In this review, we describe both the pioneering work and recent advances in our understanding of the distribution and evolution of matsutake, with a special focus on genomic studies. Deoxyribonucleic acid (DNA) sequence analyses revealed that Tricholoma caligatum was the earliest species within this group, followed by Tricholoma fulvocastaneum, the cluster with Tricholoma ilkkae, Tricholoma dulciolens, and Tricholoma bdkamatsutdke, and finally the cluster with Tricholoma murrillianum, Tricholoma mesoamericanum, Tricholoma anatolicum, and Tricholoma matsutake. Although analyses based on mobile DNAs and whole-genome sequences revealed a similar clustering pattern, there are distinct differences in the distribution of mobile DNAs and genomic structure of Tricholoma bakamatsutake and Tricholoma matsutake. Furthermore, repetitive DNA can be used as markers to distinguish among strains and populations of Tricholoma matsutake from different geographical regions, including identifying dispersals of basidiospores. 'Telomere-totelomere genome sequencing' analyses unearthed that both Tricholoma matsutake and Tricholoma bakamatsutake underwent explosive multiplications of retrotransposons within their genomes but with different mobile DNA elements expanded between them. Contrastingly the structure of the mating loci between Tricholoma matsutake and Tricholoma bakamatsutake is highly conserved. Key words: genetics, molecular ecology, prized mushroom, mycorrhiza, transposons, Introduction Matsutake are prized gourmet mushrooms consisting of the fruiting bodies of the ectomycorrhizal (EM) fungus Tricholoma matsutake (syn. T. nauseosum), particularly those associated with Pinaceae and Fagaceae (Ogawa 1978; [...]

Tricholoma matsutake is an ectomycorrhizal agaricomycete that produces the prized matsutake mushroom in conifer forests. Here, we isolated mutants generated by the argon-ion beam irradiation of T. matsutake NBRC 33136,designated asAr5002 and Ar 5012, which are defective in [beta]-1,4-endoglucanase activity, that promoted the above- andbelow-ground growth of the symbiotic partner Pinus densiflora in vitro, compared with the control. Pine seedlings associated with Ar 5002, compared with NBRC 33136, had significantly higher above-ground dry mass and significantly greater plant growth, while those associated with Ar 5012 had significantly higher above- and below-ground dry mass. There were no significant differences between the numbers of mycorrhizal root-tips synthesized by the wild-type and mutants, indicating that [beta]-1,4-endoglucanase did not influence the mycorrhization of T. matsutake. In seedlings inoculated with Ar 5002- and Ar 5012, the Hartig nets resembled those of seedlings inoculated with NBRC 33136. The data suggest that T. matsutake lacking [beta]-1,4-endoglucanase activity confer beneficial effects on the growth of P. densiflora. Further studies are necessary to determine whether the symbiotic relationship could be strengthened by such a mutated fungal trait. Key words: breeding, cellulase, heavy-ion beam mutagenesis, heterokaryon, symbiosis. Tricholoma matsutake est une ectomycorhize de la classe des Agaricomycetes qui produit dans les forets de coniferes le matsutake, un champignon prise. Les auteurs ont isole ici des mutants de T. matsutake NBRC 33136 generes par irradiation avec un faisceau d'ions argon, identifies Ar 5002 et Ar 5012, defectifs en activite [beta]-1,4-endoglucanase, qui favorisaient la croissance aerienne et souterraine du partenaire symbiotique Pinus densiflora in vitro par rapport au controle. Les plants de pin associes a Ar 5002, avaient un poids sec aerien significativement plus eleve comparativement a NBRC 33136, et une croissance significativement plus importante, tandis que ceux associes a Ar 5012 avaient des poids secs aerien et souterrain significativement plus eleves. Il n'y avait pas de difference significative quant au nombre d'extremites de racines avec mycorhizes entreletypesauvageet les mutants, ce qui indique quela [beta]-1,4-endoglucanase n'influencait pas la mycorhization par T. matsutake. QuantauxsemisinoculesparAr5002etAr5012,leursreseauxdeHartig ressemblaient a ceux des semis inocules par NBRC 33136. Les donnees suggerent que T. matsutake depourvu d'activite [beta]-1,4-endoglucanase exerce des effets benefiques sur la croissance de P. densiflora.D'autres etudes sont necessaires pour determiner si la relation symbiotique pourrait etre renforcee par un tel type de mutation chez le champignon. [Traduit par la Redaction] Mots-cles: selection, cellulase, mutagenese par faisceaux d'ions lourds, heterocaryon, symbiose., Introduction Ectomycorrhizae are a form of symbiotic relationships between fungi and certain tree species, such as those belonging to Caesalpinioideae, Dipterocarpaceae, Fagaceae, Myrtaceae, Pinaceae, and Salicaceae, and some fungal taxa, [...]

Tricholoma matsutake is an ectomycorrhizal agaricomycete that produces matsutake mushrooms in association with conifers. Here, we isolated a pleiotropic mutant, designated as G1, following 7-ray irradiation of T. matsutake NBRC 33136. In addition to exhibiting increased cellulose- and amylose-degrading activities and altered mycelial morphology, G1 degenerated lateral roots and caused stunting or fatal wilting of seedlings of its symbiotic partner, Pinus densiflora, in vitro. A mutant, designated Ar 59, previously isolated after argon-ion beam irradiation, exhibited the same phenotypes as G1, but without its detrimental effects. Ar 59, like NBRC 33136, developed a Hartig net around healthy cortical cells that was composed of uniseriate hyphae. In G1-inoculated seedlings, the Hartig net was composed of heavily bundled hyphae penetrating the intercellular space, and it was accompanied by somewhat unusual forms of plant cortical cells. Sequences of rRNA gene-related markers, including four single nucleotide polymorphisms present within each strain, were 100% identical among NBRC 33136, G1, and Ar 59, indicating that they are mutants of the wild-type. Thus, 7-ray irradiation can convert the fungus from a beneficial to a harmful agent. These findings suggest the presence of an unknown mechanism in the fungal genome that can transform mutualism into parasitism. Key words: degrading enzymes, 7-ray irradiation mutagenesis, heavy-ion beam, phenotypic transformation, plant-microbe interactions. Tricholoma matsutake est un agaromycète ectomycorhize qui produit les champignons matsutake en association avec les conifères. Les auteurs ont isolé ici un mutant pléiotropique qu'ils ont désigné G1, à la suite d'une irradiation [gamma] de T. matsutake NBRC 33136. En plus de présenter une activité accrue de dégradation de la cellulose et de l'amylose et une morphologie mycéliale modifiée, G1 provoquait la dégénérescence des racines latérales et un retard de croissance ou une flétrissure fatale des jeunes plants de son partenaire symbiotique, Pinus densiflora, in vitro. Un mutant désigné Ar 59, isolé précédemment après une irradiation à un faisceau d'argon ionisé, présentait le même phénotype que G1, mais sans les effets néfastes. Ar 59, comme NBRC 33136, développait un réseau de Hartig autour des cellules corticales saines, composé d'hyphes unisériées. Chez les plantules inoculées avec G1, le réseau de Hartig était composé d'hyphes en faisceau pénétrant l'espace intercellulaire et était accompagné par des cellules corticales végétales de formes quelque peu inhabituelles. Les séquences de marqueurs reliés aux gènes de l'ARNr, y compris quatre polymorphismes de nucléotides uniques présents dans chaque souche, étaient 100% identiques entre NBRC 33136, G1 et Ar 59, indiquant qu'ils constituent des mutants de la souche sauvage. Ainsi, l'irradiation gamme peut convertir le champignon d'une forme bénéfique en un agent pathogène. Ces données suggèrent la présence d'un mécanisme inconnu dans le génome fongique qui peut transformer le mutualisme en parasitisme. [Traduit par la Rédaction] Mots-clés : enzymes de dégradation, mutagenèse par irradiation gamma, faisceau d'ions lourds, transformation phénotypique, interactions plante-microbe., Introduction Ectomycorrhizal symbiosis occurs belowground between woody plants, belonging mostly to Caesalpinioideae, Dipterocarpaceae, Fagaceae, and Pinaceae, and filamentous fungi, belonging mostly to Ascomycota and Basidiomycota, greatly contributing to healthy forest [...]