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Paxillus ammoniavirescens
Photo credit: Hervé Gryta at EDB

Within the framework of the Mycorrhizal Genomics Initiative (MGI) and the 1000 Fungal Genomes project, we are sequencing a phylogenetically and ecologically diverse suite of mycorrhizal fungi, which include the major clades of symbiotic species associating with plants. Analyses of these genomes will provide insights into the diversity of mechanisms for the mycorrhizal symbiosis, including arbuscular, ericoid-, orchid- and ectomycorrhizal associations.

Paxillus ammoniavirescens is a recently described ectomycorrhizal species (Dessi & Contu 1999), commonly growing with planted trees, in urban areas. It belongs to the Paxillus involutus group (Boletales, Paxillaceae) but clearly differs from P. involutus, one of the most well studied ectomycorrizal fungi, and from the Paxillus rubicundulus group by its ecological characteristics.

Paxillus ammoniavirescens has a large distribution in Europe, from Scandinavia to Italy and it was also found in North Africa (Morocco). It is a highly generalist species, associated to deciduous trees (Populus, Salix, Betula, Quercus), coniferous trees (Cedrus, Pinus) and even to Eucalyptus and Cistus. It is very common in urban areas and anthropized sites (car parks, gardens, city parks) but it is also found in natural conditions, in bright places such as maquis, forest edge and river bank (Jargeat et al 2014). It grows under contrasted climatic conditions, from wet and cold climate (Sweden, Germany, England) to Mediterranean climate (Sardinia, Corsica, East South of France). Cultural features (quick growth and abundant mycelium production on synthetic medium) suggest high saprophytic capacities.

In contrast, P. involutus is restricted to forest, under fresh climate and has a limited host range (Picea, Abies, Betula). P. rubicundulus is highly specific, only associated to Alnus species and has limited saprotrophic capacities.

Thus, the genome sequence of P. ammoniavirescens, by comparaison with genome sequence other Paxillus species, will help to resolve challenging questions about the evolution of specialisation in the ectomycorrhizal symbiosis and ecological adaptations (evolution from saprophytism to biotrophy).

Several genomes of saprotrophic and ectomycorrhizal Boletales have been produced by the MGI, including Boletus edulis, Suillus luteus, Gyrodon lividus, Paxillus involutus, P. rubicundulus and Coniophora puteana. The genome of Paxillus ammoniavirescens will provide glimpse into the Boletales evolution.

The MGI is a large collaborative effort aiming for master publication(s) describing the evolution of the mycorrhizal symbioses. Researchers who wish to publish analyses using data from unpublished MGI genomes are respectfully required to contact the PIs and JGI to avoid potential conflicts on data use and coordinate other publications with the MGI master paper(s).

Genome Reference(s)