Phylogenetic relationships of the wall-synthesizing enzymes of Basidiomycota confirm the phylogeny of their subphyla.

Basidiomycota is one of the phyla of kingdom Fungi. This phylum contains besides non-pathogenic species and mushrooms, the important plant pathogens, smuts and rusts, and has been recently divided into three subphyla: Ustilaginomycotina, Pucciniomycotina, and Agaricomycotina (James et al. Nature 443:818-822, 2006; Hibbert et al. Mycological Research 111:509-547, 2007). Although the monophyletic origin of Basidiomycota appears practically undisputed, the phylogenetic relationships of the three subphyla have been considered somewhat uncertain (James et al. Nature 443:818-822, 2006). Previously, we described a hypothetical evolutionary scheme of the fungal cell wall (Ruiz-Herrera and Ortiz-Castellanos FEMS Yeast Research 10:225-243, 2010) that coincided with the accepted evolution tree of kingdom fungi (Cavalier-Smith Proceedings of the Royal Society of London B 271:1251-1262, 2004; James et al. Nature 443:818-822, 2006; Hibbert et al. Mycological Research 111:509-547, 2007). Based on the results of that study, we have now made an analysis of the phylogenetic relationships of the enzymes involved in the synthesis of the cell wall polysaccharides in Basidiomycota. According to our data, there is a close relationship of the wall-synthesizing enzymes with the accepted taxonomy of the group, with a few exceptions, noticeably the absence of chitin synthase IIb subclass in Pucciniomycotina, the duplication of chitin synthase class III in the same group, and the duplication of the gene encoding β-1,3-glucan synthase (Gls) in Agaricomycotina. These results give some clues on the evolution of the cell wall in Basidiomycota.