Paxillus rubicundulus carpophores, by Hervé Gryta.

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 endo- and ectomycorrhiza.

General description: Paxillus rubicundulus is an ectomycorrhizal basidiomycete specifically associated to alders, first described by Orton in 1969. In France, it is found associated to Alnus glutinosa and Alnus incana, in wet-lands or along rivers. This species belongs to the Paxillaceae family, in which some members are hygrophilic and highly specialized on alders, such as Paxillus rubicundulus or Gyrodon lividus while some other members have a large ecological range and are generalist, such as Paxillus involutus.

Why sequence P. rubicundulus? Comparative genomics of the generalist symbiont Paxillus involutus and the alder-specific P. rubicundulus will provide new insights on the molecular mechanisms driving host specificity amont ectomycorrhizal symbionts. In addition, the genomic sequence of the two Paxillaceae will contribute to a better understanding of their contrasted ecological strategy and the role of P. rubicundulus in the biology of alders.