Journal Article

Convergent degeneration of olfactory receptor gene repertoires in marine mammals

Zhou, Jingqi, Shen, Libing, Liu, Ake, Liu, Ruixiang, Wang, Zhijun, He, Funan

2019

Overview

Background Olfactory receptors (ORs) can bind odor molecules and play a crucial role in odor sensation. Due to the frequent gains and losses of genes during evolution, the number of OR members varies greatly among different species. However, whether the extent of gene gains/losses varies between marine mammals and related terrestrial mammals has not been clarified, and the factors that might underlie these variations are unknown. Results To address these questions, we identified more than 10,000 members of the OR family in 23 mammals and classified them into 830 orthologous gene groups (OGGs) and 281 singletons. Significant differences occurred in the number of OR repertoires and OGGs among different species. We found that all marine mammals had fewer OR genes than their related terrestrial lineages, with the fewest OR genes found in cetaceans, which may be closely related to olfactory degradation. ORs with more gene duplications or loss events tended to be under weaker purifying selection. The average gain and loss rates of OR genes in terrestrial mammals were higher than those of mammalian gene families, while the average gain and loss rates of OR genes in marine mammals were significantly lower and much higher than those of mammalian gene families, respectively. Additionally, we failed to detect any one-to-one orthologous genes in the focal species, suggesting that OR genes are not well conserved among marine mammals. Conclusions Marine mammals have experienced large numbers of OR gene losses compared with their related terrestrial lineages, which may result from the frequent birth-and-death evolution under varied functional constrains. Due to their independent degeneration, OR genes present in each lineage are not well conserved among marine mammals. Our study provides a basis for future research on the olfactory receptor function in mammals from the perspective of evolutionary trajectories.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Amino acids / Animal behavior / Animal Genetics and Genomics / Animals / Aquatic mammals / Aquatic Organisms - genetics / Biological evolution / Biomedical and Life Sciences / Comparative and evolutionary genomics / Convergent degeneration / Degeneration / Evolution / Evolution, Molecular / Evolutionary genetics / Gene Deletion / Gene families / Gene gain / Gene loss / Genes / Genetic research / Genomes / Genomics / Life Sciences / Mammals - genetics / Marine mammals / Microarrays / Microbial Genetics and Genomics / Multigene Family / Odor / Odorant receptors / Odors / Olfaction / Olfactory receptors / Orthologous gene groups / Phylogeny / Physiological aspects / Plant Genetics and Genomics / Proteins / Proteomics / Receptors / Receptors, Odorant - genetics / Research Article / Selection, Genetic / Sequence Analysis, DNA / Species / Terrestrial environments / Whales