Figure 1.
Signature of evolution of genes involved in sperm-oocyte interaction in Vertebrates.
Genes (names are indicated on the top) are classified into three main functional groups (from left to right): sperm-zona pellucida binding, acrosome reaction, and sperm-oolemma fusion. Species are indicated in the tree (left). Blue square: duplication; purple square: positive selection; pink square: duplication + positive selection. Black square: pseudogene; Black dot: no event. Black circle: no calculation of positive selection. White square: no gene found.
Figure 2.
Rate of gene appearance, gene duplication, pseudogenization, loss and intensity of positive selection in Teleostei, Aves and Eutheria. a.
Rate of events per million years (Myr) per lineage for the set of genes studied. This includes up to 69 genes, but in most cases, the number of relevant genes is lower because some types of events cannot happen in some taxa (losses or duplications cannot happen if a gene is primitively absent, and gains cannot occur in a clade if the gene appeared before the base of a given clade), and we have incorporated that factor into our calculations to obtain comparable rates across taxa. The geological age of lineages is used in the rate calculation through the phylogenetic diversity of the clades. b and c. Proportion of genes under positive selection in Teleostei, Aves and Eutheria for genes belonging to the third step, the sperm-oolemma fusion (B), and for all genes (C). Three types of confidence intervals are shown: 78%, 90% and 97% representing testing at 0.05, 0.01 and 0.001 probability thresholds, respectively. Statistically significant comparisons, for which confidence intervals do not overlap, are indicated.
Figure 3.
3D structures of N and C domain of ACE in platypus, Xenopus, chimpanzee and zebrafish.
ACE structures have been modeled for four species based on human PDB structure (PDB: 1O8A) [36]. This enzyme is composed of two homolog N and C domains, each containing a catalytic site composed by two histidines in a conserved -HEXXH- zinc-binding motif [37] and a glutamate as the third ligand 24 residues downstream this motif [38]. These three binding sites are indicated in yellow, whereas amino acids under positive selection are in pink. ACE protein is expressed by sperm. Gene knockout experiments of ACE in mouse results in an impaired uterotubular sperm migration and a reduced ability to bind the zona pellucida of the egg [39], [40], [41].