TY  - JOUR
AU  - Delaye, Luis
PY  - 2019
DA  - 2019/07/11
TI  - Genes Coding for GPI Biosynthesis in <i>Pneumocystis</i> Experienced Relaxed Selection: A Follow-up Study
JO  - OBM Genetics
SP  - 083
VL  - 03
IS  - 03
AB  - Background: Phylogenetic analyses shows that Pneumocystis species have coevolved with their mammalian hosts for millions of years. As a result, infection by Pneumocystis is species specific (i.e. a given Pneumocystis species can infect only a single species of host). This specificity suggests the existence of a Red-Queen dynamic between Pneumocystis and its host. Evidence of this dynamic is provided by the molecular diversity and the elevated rate of non-synonymous versus synonymous (dN/dS) codon substitutions among Pneumocystis major surface glycoproteins (MSG). It was previously suggested that this evolutionary dynamic also affected the evolution of genes coding for the biosynthesis of glycosylphosphatidylinositol (GPI). This was based on the fact that MSG are targeted to the cell surface by GPI and GPI biosynthetic genes showed a statistically significant increase in their dN/dS rate when compared to other groups of genes in Pneumocystis genome. Here we test whether GPI biosynthetic genes increased their omega rate by positive or by relaxation of natural selection.
Methods: Genes coding for the biosynthesis of glycosylphosphatidylinositol (GPI) in Pneumocystis and closely related fungi were retrieved from Genbank. Each one of the retrieved gene families were analysed with RELAX software to discriminate between positive or relaxed selection. In addition, we searched for evidences of episodic selection in these genes by using aBSREL and analysed their dN/dS rate by using the branch model as implemented in CodeML.
Results: Molecular phylogenetic analyses showed that the set of genes coding for the biosynthesis of GPI suffered relaxed selection. In just 4 of the 19 gene families studied here we were able to detect evidences of episodic selection. In addition, the results of the CodeML branch model are consistent with evolution by relaxed selection.
Conclusions: The relaxation of selection in GPI biosynthetic genes is not consistent with the previous proposal suggesting that positive selection increased the dN/dS rate of these genes due to a Red-Queen dynamic between Pneumocystis and its host. Despite the statistical significance previously reported, the increase in the omega rate in this group of genes still requires biological interpretation. Further genome wide analysis to distinguish between intensification or relaxation of selection in protein coding genes, are needed to better understand the evolution Pneumocystis.
SN  - 2577-5790
UR  - https://doi.org/10.21926/obm.genet.1903083
DO  - 10.21926/obm.genet.1903083
ID  - Delaye2019
ER  -