title: Functional evolution of duplicated odorant-binding protein genes, Obp57d and Obp57e, in Drosophila.
abstract: Odorant-binding proteins (OBPs) are extracellular proteins found in insect chemosensilla, where they participate in the sensing of odors, tastes, and pheromones. Although a large number of OBP genes have been identified in insect genomes, their molecular functions and biological roles have been clarified in limited cases. Two OBP genes, Obp57d and Obp57e, were involved in the evolution of host-plant preference in Drosophila sechellia. Comparative analyses of the Obp57d/e genomic sequences from 27 closely related species suggested that the two genes arose by tandem gene duplication and functionally diverged from each other. In this study, the functional evolution of Obp57d and Obp57e was examined by in vitro binding assays using recombinant proteins synthesized in a bacterial system. Compared to the ancestral Dpse\OBP57de, Dmel\OBP57d was more specialized to tridecanoic acid while Dmel\OBP57e was generalized regarding their binding affinity, suggesting that the two OBP genes underwent subfunctionalization and neofunctionalization. A behavioral analysis using knockout flies supported that the biological role is different between OBP57d and OBP57e in vivo. Site-directed mutagenesis of the evolutionarily conserved amino acids revealed that these residues play an important role in protein folding. These findings provide a clue to understanding how the repertoire of OBP genes is maintained in a genome under natural selection.
authors.affiliation: Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo, Japan.
authors.forename: Eriko
authors.initials: E
authors.lastname: Harada
authors.forename: Jun
authors.initials: J
authors.lastname: Nakagawa
authors.forename: Tsunaki
authors.initials: T
authors.lastname: Asano
authors.forename: Masato
authors.initials: M
authors.lastname: Taoka
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Sorimachi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Ito
authors.forename: Toshiro
authors.initials: T
authors.lastname: Aigaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Matsuo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002633:Chemotaxis / Q000235:genetics / Q000502:physiology; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D005260:Female; D020131:Genes, Duplicate; D008969:Molecular Sequence Data; D010058:Oviposition / Q000235:genetics; D011485:Protein Binding; D018035:Receptors, Odorant / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017385:Sequence Homology; D013050:Spectrometry, Fluorescence
chemical_list: D029721:Drosophila Proteins; C529204:Obp57d protein, Drosophila; C505437:Obp57e protein, Drosophila; D018035:Receptors, Odorant; D011994:Recombinant Proteins