The Archaeorhizomycetes and the 'cryptomycota'

[tripsis]

Discovery of novel intermediate forms redefines the fungal tree of life

Meredith D. M. Jones, Irene Forn, Catarina Gadelha, Martin J. Egan, David Bass, Ramon Massana & Thomas A. Richards

Nature 474, 200–203 (09 June 2011) doi:10.1038/nature09984

Fungi are the principal degraders of biomass in terrestrial ecosystems and establish important interactions with plants and animals1, 2, 3. However, our current understanding of fungal evolutionary diversity is incomplete4 and is based upon species amenable to growth in culture1. These culturable fungi are typically yeast or filamentous forms, bound by a rigid cell wall rich in chitin. Evolution of this body plan was thought critical for the success of the Fungi, enabling them to adapt to heterogeneous habitats and live by osmotrophy: extracellular digestion followed by nutrient uptake5. Here we investigate the ecology and cell biology of a previously undescribed and highly diverse form of eukaryotic life that branches with the Fungi, using environmental DNA analyses combined with fluorescent detection via DNA probes. This clade is present in numerous ecosystems including soil, freshwater and aquatic sediments. Phylogenetic analyses using multiple ribosomal RNA genes place this clade with Rozella, the putative primary branch of the fungal kingdom1. Tyramide signal amplification coupled with group-specific fluorescence in situ hybridization reveals that the target cells are small eukaryotes of 3–5 μm in length, capable of forming a microtubule-based flagellum. Co-staining with cell wall markers demonstrates that representatives from the clade do not produce a chitin-rich cell wall during any of the life cycle stages observed and therefore do not conform to the standard fungal body plan5. We name this highly diverse clade the cryptomycota in anticipation of formal classification.

Archaeorhizomycetes: Unearthing an Ancient Class of Ubiquitous Soil Fungi

Anna Rosling, et al.

DOI: 10.1126/science.1206958

Science 333, 876 (2011);

Abstract

Estimates suggest that only one-tenth of the true fungal diversity has been described. Among numerous fungal lineages known only from environmental DNA sequences, Soil Clone Group 1 is the most ubiquitous. These globally distributed fungi may dominate below-ground fungal communities, but their placement in the fungal tree of life has been uncertain. Here, we report cultures of this group and describe the class, Archaeorhizomycetes, phylogenetically placed within subphylum Taphrinomycotina in the Ascomycota. Archaeorhizomycetes comprises hundreds of cryptically reproducing filamentous species that do not form recognizable mycorrhizal structures and have saprotrophic potential, yet are omnipresent in roots and rhizosphere soil and show ecosystem and host root habitat specificity.

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Edited August 31, 2011 by tripsis