Within the framework of the JGI Mycorrhizal Genomics Initiative, we are sequencing a phylogenetically and ecologically diverse suite of mycorrhizal fungi (Basidiomycota and Ascomycota), which include the major clades of symbiotic species associating with trees and woody shrubs. Analyses of these genomes will provide insight into the diversity of mechanisms for the mycorrhizal symbiosis,including ericoid-, orchid- and ectomycorrhizal associations.
Tricholoma matsutake - The Buddha Mushroom
Tricholoma matsutake (S. Ito & S.Imai) Singer (syn. T. nauseosum), so-called Matsutake or pine mushroom, belongs to the Agaricales (Tricholomataceae). This basidiomycete forms a symbiotic relationship with the roots of a limited number of tree species. In Japan it is most commonly associated with Japanese Red Pine. However in the North American Pacific Northwest it is found in coniferous forests made up of one or more of the following species: Douglas-fir, Noble Fir, Shasta Red Fir, Sugar Pine, Ponderosa Pine or Lodgepole Pine. In California, it is also associated with hardwoods, including Tanoak and Madrone. Matsutake fruiting bodies are usually concealed under fallen leaves and duff on the forest floor. T. matsutake forms a solid, tight white aggregate of mycelia and mycorrhizas below the litter layer called a "shiro". T. matsutake lives mainly as an ectomycorrhizal symbiont but can also feed as a saprotroph. A flexible trophic ecology confers T. matsutake with a clear advantage in a complex soil litter environment and during sporocarp development.
Matsutake is highly prized by Japanese and Chinese for its distinct spicy-aromatic odor and distinctive taste. One kg of top-quality fresh matsutake may be sold for as much as US $2000. However, in the past century in Japan, because of deforestation and infestation by the pinewood nematode (Bursaphelenchus xylophilus), populations of the matsutake mushroom host plant Pinus densiflora have declined rapidly. As a result, the annual harvest of matsutake in Japan has been declining steadily, and is much lower than in the early twentieth century. Most matsutake is imported, although demand still outstrips supply.
The available genome will allow to study the symbiosis molecular toolbox of this fungus related to the model ectomycorrhizal species L. bicolor and investigate whether it is using small secreted proteins to interact with the host plants. It will also facilitate the analysis of pathways involved in synthesis of mushroom's flavor, to carry out research on the production of mushrooms.