Phylogenetic analysis of the Glomeromycota by partial β-tubulin gene sequences

Abstract

The 3' end of the beta-tubulin gene was amplified from 50 isolates of 45 species in Glomeromycota. The analyses included a representative selection of all families except Pacisporaceae and Geosiphonaceae. Phylogenetic analyses excluded three intron regions at the same relative positions in all species due to sequence and length polymorphisms. The beta-tubulin gene phylogeny was similar to the 18S rRNA gene phylogeny at the family and species level, but it was not concordant at the order level. Species in Gigasporaceae and Glomeraceae grouped together but without statistical support. Paralogous sequences in Glomus species likely contributed to phylogenetic ambiguity. Trees generated using different fungal phyla as out-groups yielded a concordant topology. Family relationships within the Glomeromycota did not change regardless if the third codon position was included or excluded from the analysis. Multiple clones from three isolates of Scutellospora heterogama yielded divergent sequences. However, phylogenetic patterns suggested that only a single copy of the beta-tubulin gene was present, with variation attributed to intraspecific sequence divergence.

<I>Glomus candidum</I>, a new species of arbuscular mycorrhizal fungi from North American grassland

“…This is consistent with the phylogeny generated by the β-tubulin gene using an isolate of G. candidum from Maryland (Msiska & Morton 2009). Both of these studies were limited by using only a single sequence from a single spore of the new AM fungal species.…”

“…In addition, in G. clarum and G. manihotis the external mucilaginous layer reacts strongly in Melzer's reagent (pinkish-red to light purple), while the reaction of the same layer in G. candidum is very pale pink and only occurs in juvenile spores. Finally, molecular tools clearly identify that G. candidum is a member of Glomus group B, while G. diaphanum, G. clarum, and G. manihotis are in Glomus group A sensu Schwarzott et al (2001) (Msiska & Morton 2009). …”

Taxonomic revision transferring species inKuklosporatoAcaulospora(Glomeromycota) and a description ofAcaulospora colliculosasp. nov. from field collected spores

“…Analysis of the SSU nrRNA gene also indicated that A. colombiana and an undescribed entrophosporoid species (WV201) nest within Acaulospora instead of as a unique monophyletic group (Walker et al 2004). Similarly A. colombiana and A. kentinensis evolved from different immediate ancestors based on a phylogeny of partial sequences of the b-tubulin gene (Msiska and Morton 2009). Thus gene phylogenies within Acaulosporaceae indicate the entrophosporoid mode of spore formation is not a synapomorphy that defines a unique monophyletic group.…”

Phosphate Transporter Genes as Reliable Gene Markers for the Identification and Discrimination of Arbuscular Mycorrhizal Fungi in the Genus Glomus

“…The intrasporal variability in ribosomal DNA (rDNA) sequences (16,17,20,27) is sometimes much higher than the interspecific variation (7,25), and the phylogenetic overlap of sequences across species is a real problem with respect to identification. The use of protein-encoding genes for actin (15), tubulin (9,10,19), and P-type H ϩ -ATPase (9, 11) has already been investigated, but with limited success, while genes for ef1-alpha, V-H ϩ -ATPase, and F-ATPase ␤-subunit (30) seem efficacious only for discriminating between unrelated Glomus species. The expression profiles of a phosphate transporter (PT) gene of three Glomus species have been studied (4,18), and the gene was considered a promising avenue for the identification of AM fungi (13).…”