जेनेटिक्स और जीनोम जर्नल

Molecular Identification and Characterisation of Olfactory Receptor Genes among Fruit and Insect Eating Bats

Abstract

Thangavel Karuppudurai*, Steffi Christiane Ramesh and Sowmya V Bhat

Among vertebrates, olfaction is deemed the oldest and most valuable modes of sensory perception, nevertheless remain the least understood modalities. Most organisms use olfaction at varying grades in all aspects of their life to detect food, avoid predators and for mate choice. The olfactory receptor (OR) gene repertoire is the largest gene family within the mammalian genome. Although the OR gene superfamily constitutes 3 to 6% of mammalian genes and is well annotated and completed in the human and mouse genomes, it is still unclear which odorants bind to which receptors and how this complex process translates into recognising a specific smell. Examining the relatively closely related species that exhibit a high dietary diversity and olfaction can help discern the olfactory receptor genes identification and characterisation. Bats are potentially useful for this purpose. Bats represent one of the most fascinating mammals for studying the OR genes identification and characterisation, since bats exhibit an excellent olfactory performance. The OR genes identification studies among bat species have been rare in India. In fact, until recently, there is no systematic study of OR genes identification and characterisation in bats. In this study, we employ bioinformatics and molecular biology approaches to identify the unique and diverse OR genomic repertoire in bats. Our sequencing results suggest that both fruit and insect eating bat species expressed different OR genes. Over all a total of 37 OR genes (9 gene families) were identified from 10 different bat species. We generated a global multiple alignment of the deduced amino acid sequences of 37 OR genes from 10 bat species. The most variable region was found to be TM segments 3, 4 and 5, within which 17 hypervariable regions were identified. These regions which constitute the odorant complementarity determining regions are the potential sites for ligand binding. Taken together, our results suggest that the total number of OR genes and families vary widely among both fruit and insect eating bats. The wide variety of sensory specializations and modalities in bats could explain the variety and distinctness of the bat OR repertoire if reflected in the OR gene diversity.