Ceratobasidium sp. (anastomosis group I, AG-I) v1.0
Ceratobasidium sp. anastomosis group I; DN8442
(a - c) Ceratobasidium sp. (anastomosis group I; DN8442) growing on PDA medium. (a) Fungal colony. (b) Hyphae. (c) A typical Rhizoctonia branching pattern. (d - f) Symbiotically germinated seeds with DN8442, forming (d) protocorms and (e) a seedling of Spiranthes sinensis var. amoena. (f) A longitudinal half section of a protocorm, showing fungal colonization in cells of the basal part (on the left ) but not in those of the meristematic region (on the right). Photo credit: Yukari Kuga

Within the framework of the Mycorrhizal Genomics Initiative (MGI) and the 1000 Fungal Genomes (1KFG) 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.

Ceratobasidium sp. (anastomosis group I; AG-I)

The genus Ceratobasidium is a member of the phylum Basidiomycota (Cantharellales, Ceratobasidiaceae), categorized in corticoid fungi and distributed worldwide. The anamorphic genus Ceratorhiza was assigned to Ceratobasidium; for a long period, however, this fungal group has been known as binucleate Rhizoctonia (BNR) and divided into anastomosis groups (AGs). Some AGs produced teleomorphs in laboratories, and their taxonomic relationship with Ceratobasidium species was confirmed. DN8442 was originally isolated from a mycorrhizal root of the terrestrial orchid species Dactylorhiza aristata, intermixed with Spiranthes sinensis. Seeds of S. sinensis symbiotically germinate with the DN8442 isolate and form protocorms and mycorrhizal adult plants. Therefore, this combination has been used as a model system to investigate orchid symbiosis. Research includes studies on ultrastructure, enzyme cytochemistry, host microtubule/actin filament arrays, etc. Recently, C and N transfers at the cellular level were documented using stable-isotope tracers and isotope microscopy; mechanisms of nutrient transfer are of major interest to understand mycorrhizal functions.

The MGI and 1KFG are large collaborative efforts aiming for master publication(s) describing the evolution of the mycorrhizal symbioses. Researchers who wish to publish analyses using data from unpublished MGI and 1KFG genomes are respectfully required to contact the PIs and JGI to avoid potential conflicts on data use and coordinate other publications with the MGI and 1KFG master paper(s).