Fusion of the subunits α and β of succinyl-CoA synthetase as a phylogenetic marker for Pezizomycotina fungi

Abstract

Gene fusions, yielding the formation of multidomain proteins, are evolutionary events that can be utilized as phylogenetic markers. Here we describe a fusion gene comprising the α and β subunits of succinyl-coA synthetase, an enzyme of the TCA cycle, in Pezizomycotina fungi. This fusion is present in all Pezizomycotina with complete genome sequences and absent from all other organisms. Phylogenetic analysis of the α and β subunits of succinyl-CoA synthetase suggests that both subunits were duplicated and retained in Pezizomycotina while one copy was lost from other fungi. One of the duplicated copies was then fused in Pezizomycotina. Our results suggest that the fusion of the α and β subunits of succinyl-CoA synthetase can be used as a molecular marker for membership in the Pezizomycotina subphylum. If a species has the fusion it can be reliably classified as Pezizomycotina, while the absence of the fusion is suggestive that the species is not a member of this subphylum.

Keywords: evolutionary marker; fungi phylogeny; fused genes.

Figure 1

Phylogenetic trees of the α subunit of succinyl-CoA synthetase in fungi. Pezizomycotina sequences are in blue, Saccharomycotina in green, Taphrinomycotina in red and Basidiomycota in gray. Neocallimastigomycotina and Metazoans (outgroup) are in black. Dashed lines represent fused genes. Bootstrap support values are given in relevant nodes. (a) Mr Bayes tree; (b) PhyML Maximum likelihood tree.

Figure 2

Phylogenetic tree of the β subunit of succinyl-CoA synthetase in fungi. Pezyzomycotina sequences are in blue, Saccharomycotina in green, Taphrinomycotina in red and Basidiomycota in gray. Neocallimastigomycotina and Metazoans (outgroup) are in black. Dashed lines represent fused genes. Bootstrap support values are given in relevant nodes. (a) Mr Bayes tree; (b) PhyML Maximum likelihood tree.