Comparative genomics of chemosensory protein genes reveals rapid evolution and positive selection in ant-specific duplicates

Abstract

Gene duplications can have a major role in adaptation, and gene families underlying chemosensation are particularly interesting due to their essential role in chemical recognition of mates, predators and food resources. Social insects add yet another dimension to the study of chemosensory genomics, as the key components of their social life rely on chemical communication. Still, chemosensory gene families are little studied in social insects. Here we annotated chemosensory protein (CSP) genes from seven ant genomes and studied their evolution. The number of functional CSP genes ranges from 11 to 21 depending on species, and the estimated rates of gene birth and death indicate high turnover of genes. Ant CSP genes include seven conservative orthologous groups present in all the ants, and a group of genes that has expanded independently in different ant lineages. Interestingly, the expanded group of genes has a differing mode of evolution from the orthologous groups. The expanded group shows rapid evolution as indicated by a high dN/dS (nonsynonymous to synonymous changes) ratio, several sites under positive selection and many pseudogenes, whereas the genes in the seven orthologous groups evolve slowly under purifying selection and include only one pseudogene. These results show that adaptive changes have played a role in ant CSP evolution. The expanded group of ant-specific genes is phylogenetically close to a conservative orthologous group CSP7, which includes genes known to be involved in ant nestmate recognition, raising an interesting possibility that the expanded CSPs function in ant chemical communication.

Comparative genomics and transcriptomics in ants provide new insights into the evolution and function of odorant binding and chemosensory proteins

“…In contrast to previous hypotheses [17, 18], it is primarily a conserved subset of single-copy orthologs which are expressed in ant antennae. In Cerapachys biroi , only one dynamically evolving CSP is expressed specifically in antennae, in contrast to five conserved OBPs and two conserved CSPs showing antenna-specific expression.…”

A comparative study of egg recognition signature mixtures inFormicaants

“…Single species studies have been useful in demonstrating identity of recognition cues, and the kinds of selection acting on underlying gene sequences, for example, in fungi (Hall et al ), colonial ascidians (Nydam and De Tomaso ), and Dictyostelium (Benabentos et al ). Similarly, comparisons on broad phylogenetic scales have revealed the evolutionary forces acting on recognition gene families (Gadau et al ; Zhou et al ; Kulmuni and Havukainen ; Kulmuni et al ) and recognition cues (Van Wilgenburg et al ). However, to understand the evolutionary forces acting on phenotypic cue variability, and which cues are informative in which context, patterns of natural variation need to be broadly described with comparative studies of closely related species.…”

Gene Turnover Contributes to the Evolutionary Adaptation of Acidithiobacillus caldus: Insights from Comparative Genomics

“…Another view is that the substitution rates for beneficial and deleterious mutations depend on environmental selection, as well as population size and structure (Gillespie, 1991; Ohta, 1992). For many years, the crucial role of gene and genome duplications (namely, neofunctionalization and subfunctionalization) in governing organismal evolution has been acknowledged (Ohno, 1970; Force et al, 1999; Innan and Kondrashov, 2010; Kulmuni et al, 2013). Only in recent decades has great attention been paid to the molecular mechanisms of gene loss (deletion or pseudogenization) as a pervasive source of genetic change, which is believed to be another key evolutionary event that causes adaptive phenotypic diversity (Albalat and Cañestro, 2016).…”