Bacterial origin of insect chemosensory odor binding proteins

Abstract

Two families of small soluble binding proteins, namely chemosensory proteins (CSPs) and odor binding proteins (OBPs), were for long considered to play a key role in insect olfaction. A chemosensory protein-encoding gene was identified in the sweet potato whitefly Bemisia tabaci , which displayed high sequence homology with genes of plant origin. Such genetic hallmark sent the origin of CSPs back to horizontal gene transfer through bacteria in their early stages of the association with insects and plants, and thereby to a function most likely unrelated to olfaction. Similarly, identification of OBP-RNA in bacillus proteobacter Acinetobacter baumannii indicates that not only CSPs, but also OBPs peek back through many successive generations all the way from prokaryotic time at very far distant period in evolution. The co-occurrence of CSP/OBP in bacteria strongly suggests that the two protein families have evolved from an ancestor molecule possibly associated with abiogenesis and origin of life.