Odorant binding protein diversity and distribution among the insect orders, as indicated by LAP, an OBP-related protein of the true bug Lygus lineolaris (Hemiptera, Heteroptera)

Insect odorant binding proteins (OBPs) are thought to deliver odors to olfa ctory receptors, and thus may be the first biochemical step in odor recepti on capable of some level of odor discrimination. OBPs have been identified from numerous species of several insect orders, including Lepidoptera, Dipt era, Coleoptera and Hymenoptera; all are holometabolous insects belonging t o the monophyletic division of insects known as the Endopterygota. Recently , an antennal protein with OBP-like properties was identified from Lygus li neolaris, a hemipteran insect representing the Hemipteroid Assemblage, a si ster division to the Endopterygota. The full length sequence of Lygus anten nal protein (LAP) is presented in this report. In situ hybridization analys is revealed LAP expression in cell clusters associating with olfactory sens illa; expression was adult-specific, initiating in developing adult tissue during the transitional period that precedes the actual adult molt. Sequenc e analysis confirmed that LAP is homologous with the OBP-related protein fa mily and most similar ito the OS-E and OS-F proteins of Drosophila, the ABP X proteins of Lepidoptera and the OBPRP proteins of the Coleoptera. Assumin g that the OBP-related proteins represent one homologous family, the identi fication of LAP significantly expands the phylogenetic depth of that family and its underlying role in odor detection to encompass all members of the Endopterygota and Hemipteroid Assemblage, which comprise >90% of all insect species.