Leptodontium sp. PMI_412 v1.0
Leptodontidium sp. PMI 412. Photo credit: Gregory Bonito
Leptodontidium sp. PMI 412. Photo credit: Gregory Bonito

Leptodontidium is a genus of root-associated fungi that belong to the morphological species-complex described by Melin in 1922 as Mycelium radices atrovirens (MRA)1 and formally described by de Hoog in 1979 2. This genus belongs within the diverse order of Helotiales (Ascomycota). This genome sequenced isolate “Leptodontidium sp. PMI 412” was isolated from healthy Populus deltoides roots collected from a native riparian habitat along the Yadkin River in North Carolina. This isolate is closely related to Leptodontidium orchidicola, an endophyte originally described from orchid roots in Canada. The Leptodontidium orchidicola species-complex has not been resolved and appears to be globally distributed and associated with roots of a high diversity of plant hosts. The clade where this sequenced strain belongs contains several genera of fungi (e.g., Meliniomyces, Phialocephala, Cadophora) that have been isolated from roots of a high diversity of plant species and are known collectively as “dark septate endophyte” (DSE) fungi. The role of the DSEs in ecosystem functioning is still elusive and their interaction with plants is not as well understood as the more studied ectomycorrhizal and arbuscular mycorrhizal fungi. Leptodontidium orchidicola has been shown to form a range of symbiotic associations with Salix that could be considered mutualistic to parasitic, depending on environmental context. It is interesting to note that DSE fungi are able to colonize the roots of mycorrhizal plants such as Populus and Pine as well as non-mycorrhizal plants, such as Brassica napus (rapeseed), all of which are important to biofuel industries. We hypothesize that root-endophytes represent a guild of unique plant-fungal interactions. Genomic studies comparing these fungi to other symbiotic and saprotrophic fungi might help us to better understand their role in carbon cycling and ecosystem functioning.

References

1. Melin, E. On the mycorrhizas of Pinus sylvestris L. and Picea abies Karst. A preliminary note. J. Ecol. 9, 254–257 (1922).
de Hoog, G. S. Rhinocladiella and allied genera. Taxon 28, 347–384 (1979).
2. Fernando, A. & Currah, R. A comparative study of the effects of the root endophytes Leptodontidium orchidicola and Phialocephala fortinii (Fungi Imperfecti) on the growth of some subalpine. Can. J. Bot. 74, 1071–1078 (1996).