Monophyly of β- tubulin and H+- ATPase gene variants in Glomus intraradices: consequences for molecular evolutionary studies of AM fungal genes

• Published in: Fungal genetics and biology 2004-02, Vol.41 (2), p.262-273
• Main Authors: Corradi, Nicolas, Kuhn, Gerrit, Sanders, Ian R.
• Format: Article
• Language: English
• Subjects: Base Composition - genetics; DNA, Fungal - chemistry; DNA, Fungal - isolation & purification; Evolution, Molecular; Genes, Fungal - genetics; Genetic Variation; Molecular Sequence Data; Mycorrhizae - classification; Mycorrhizae - genetics; Phylogeny; Sequence Analysis, DNA; Tubulin - genetics; Vacuolar Proton-Translocating ATPases - genetics
• ISSN: 1087-1845; 1096-0937
• DOI: 10.1016/j.fgb.2003.11.001

Arbuscular mycorrhizal fungi (AMF) are an ecologically important group of fungi. Previous studies showed the presence of divergent copies of β- tubulin and V-type vacuolar H +- ATPase genes in AMF genomes and suggested horizontal gene transfer from host plants or mycoparasites to AMF. We sequenced these genes from DNA isolated from an in vitro cultured isolate of Glomus intraradices that was free of any obvious contaminants. We found two highly variable β- tubulin sequences and variable H +- ATPase sequences. Despite this high variation, comparison of the sequences with those in gene banks supported a glomeromycotan origin of G. intraradices β- tubulin and H +- ATPase sequences. Thus, our results are in sharp contrast with the previously reported polyphyletic origin of those genes. We present evidence that some highly divergent sequences of β- tubulin and H +- ATPase deposited in the databases are likely to be contaminants. We therefore reject the prediction of horizontal transfer to AMF genomes. High differences in GC content between glomeromycotan sequences and sequences grouping in other lineages are shown and we suggest they can be used as an indicator to detect such contaminants. H +- ATPase phylogeny gave unexpected results and failed to resolve fungi as a natural group. β- Tubulin phylogeny supported Glomeromeromycota as sister group of the Chytridiomycota. Contrasts between our results and trees previously generated using rDNA sequences are discussed. Index descriptors: Arbuscular mycorrhizal fungi; β- tubulin; H +- ATPase; Contamination; Phylogeny; Monophyly; Molecular variation; Culturing system