July 25, 2014
African Elephant Genome Suggests They Are Superior Smellers
Sense of smell is critical for survival in many mammals. The ability to distinguish different odors, which is important for sniffing out food, avoiding predators, and finding mates, depends on the number and type olfactory receptors found in an organism's genome. In a study published this week in Genome Research, researchers examined the olfactory receptor (OR) repertoire encoded in 13 mammalian species and found that African elephants have the largest number of OR genes ever characterized; more than twice that found in dogs, and five times more than in humans.
The authors traced the evolutionary histories of OR genes using a novel computational tool to deduce ancestral genes, and then examined their duplication or loss in each species. Some lineages of OR genes greatly expanded in a given species, such as an ancestral gene that has duplicated in elephants, generating 84 distinct genes (humans and other primates only have 1 copy), while other OR gene lineages are completely lost. Each species' unique olfactory repertoire, resulting from hundreds of gene duplications and deletions during evolution, highlights the molecular basis for differences in olfaction across organisms.
"Comparison of the repertoires of OR genes among mammals lets us know the commonalities and differences of olfactory perception, deepening our understanding of the sense of smell in humans," Niimura said.