Abstract
Olfaction, which is mediated by olfactory receptor (OR) genes, is essential in the daily life of fish, especially in foraging. However, Chinese perch (Siniperca chuatsi) is believed to prey with reliance on vision and lateral sensation, but not on olfaction. Therefore, understanding the evolutionary dynamics of the Chinese perch OR repertoire could provide insights into genetic evidence for adapting to a decreasing reliance on olfaction. Here, we reported a whole-genome analysis of the Chinese perch OR repertoire. Our analysis identified a total of 152 OR genes, including 123 functional genes and 29 pseudogenes, and showed their genomic organization. A phylogenetic tree was constructed, and the phylogenetic relationships of teleosts ORs was illustrated. The dN/dS (global ratios of non-synonymous to synonymous) analysis demonstrated that OR groups all appeared to be under purifying selection. Among the five Percomorpha fishes, Chinese perch only had 22 subfamilies, suggesting a decrease in OR diversities. The species-specific loss of subfamily 56 and 66 in Chinese perch, of which the genes belonged to subfamily 66, were orthologs of OR51E2, which recognized the plant odorant β-ionone, indicating that extremely piscivorous fish which might lose those receptors responded to plant-related odors. Finally, the expression profiles of OR genes in the olfactory epithelium at different developmental stages were investigated using RNA-seq data. From the aforementioned results, the evolution of the OR repertoire may be shaped by the adaption of vision-dependent specializations for foraging in Chinese perch. The first systematic study of OR genes in Chinese perch could provide valuable genomic resources for the further investigation of olfactory function in teleosts.
Highlights
IntroductionIt is well-known that animals have five basic senses (olfaction, vision, gustation, hearing, and touch), which are of fundamental importance in the lives of animals
It is well-known that animals have five basic senses, which are of fundamental importance in the lives of animals
This study provides the first comprehensive and systematic analysis of the olfactory receptor (OR) repertoire in Chinese perch
Summary
It is well-known that animals have five basic senses (olfaction, vision, gustation, hearing, and touch), which are of fundamental importance in the lives of animals. One or more of the five senses could be absent in some species, such as whales, which lack the specific olfactory functions that induce innate avoidance behaviors against odors of predators and spoiled foods [1]. The sense of smell, or olfaction, is mediated by olfactory receptors (ORs), which are mainly responsible for the perception and detection of tens of thousands of chemical odors. Olfaction is essential for fish survival, due to its action in recognizing appropriate food, relatives, offspring, habitats, and predator avoidance [2,3,4,5]. ORs are G-protein-coupled receptors (GPCR) with seven-transmembrane domains, encoded by OR genes [10]. The OR genes make up one of the largest gene superfamilies in most animal genomes
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