A comparative study of odorant binding protein genes: differential expression of the PBP1-GOBP2 gene cluster inManduca sexta(Lepidoptera) and the organization of OBP genes inDrosophila melanogaster(Diptera)

Abstract

SUMMARYInsects discriminate odors using sensory organs called olfactory sensilla, which display a wide range of phenotypes. Sensilla express ensembles of proteins, including odorant binding proteins (OBPs), olfactory receptors (ORs) and odor degrading enzymes (ODEs); odors are thought to be transported to ORs by OBPs and subsequently degraded by ODEs. These proteins belong to multigene families. The unique combinatorial expression of specific members of each of these gene families determines, in part, the phenotype of a sensillum and what odors it can detect. Furthermore, OBPs, ORs and ODEs are expressed in different cell types, suggesting the need for cell–cell communication to coordinate their expression. This report examines the OBP gene family. In Manduca sexta, the genes encoding PBP1Msex and GOBP2Msex are sequenced, shown to be adjacent to one another, and characterized together with OBP gene structures of other lepidoptera and Drosophila melanogaster. Expression of PBP1Msex, GOBP1Msex and GOBP2Msex is characterized in adult male and female antenna and in larval antenna and maxilla. The genomic organization of 25 D. melanogaster OBPs are characterized with respect to gene locus, gene cluster, amino acid sequence similarity, exon conservation and proximity to OR loci, and their sequences are compared with 14 M. sexta OBPs. Sensilla serve as portals of important behavioral information, and genes supporting sensilla function are presumably under significant evolutionary selective pressures. This study provides a basis for studying the evolution of the OBP gene family, the regulatory mechanisms governing the coordinated expression of OBPs, ORs and ODEs, and the processes that determine specific sensillum phenotypes.

An Expanded Survey of the Moth PBP/GOBP Clade in Bombyx mori: New Insight into Expression and Functional Roles

“…Like EST-RNA sequences, RT-PCR products for PBP1, PBP2, GOBP1 , and GOBP2 genes do not necessarily signify the presence of the respective proteins, but they certainly signify the induction of the respective genes not only in the egg but also in many tissues of the larvae of the silkworm moth (see Figure 4 ). In the fifth instar larvae (feeding stage) of the silkworm B. mori , we find the induction of the GOBP1 and GOBP2 expression to be mainly associated with the mouthparts, confirming the studies of Vogt et al ( 2002 ). However, our results show that GOBP1 expression is not restricted to chemosensory sensilla surrounding the mouth, but that GOBP1 RNA transcripts are also particularly abundant in the secretory section (rich in fibroin) and the storage sac (unspun silk) of the moth silk gland (see Figure 4A ).…”

“…Pheromone-binding proteins and general odorant-binding proteins are very well-recognized members of the larger odorant binding protein gene family, which has been shown to be represented in most insect lineages and species (Picimbon, 2003 ; Li et al, 2008 ; He et al, 2011 ; Iovinella et al, 2011 ; Donnell, 2014 ; Ozaki, 2019 ). Pheromone-binding proteins (PBPs) and general odorant-binding proteins (GOBPs) are particularly notable because (1) they comprise a Lepidoptera-specific clade within the larger insect OBP gene family; (2) they comprise a single gene cluster that arose through early gene duplication; and (3) they are the original genes identified that establish the OBP gene family (Vogt et al, 1989 , 1991a , b , 2002 ; Picimbon, 2003 , 2005 , 2019 ; Abraham et al, 2005 ; Vogt, 2005 ).…”

“…Originally, PBP and GOBP in adult moths were considered to be absent from the thorax, midgut, fat body, and metabolic tissues but abundant in the antennae and legs; this also included proteins/genes of the current study, namely, “PBP1, PBP2, GOBP1, and GOBP2” of the silkworm moth, B. mori (BmorPBP1, BmorPBP2, BmorGOBP1, and BmorGOBP2; Vogt et al, 1991a , b ; Krieger et al, 1996 ; Sandler et al, 2000 ; Forstner et al, 2006 ; Gong D. et al, 2009 ; Zhou et al, 2009 ; Li et al, 2012 ; Xuan et al, 2014 ; Picimbon, 2019 ). In addition, while the larval expression of GOBP2 was restricted to large sensilla basiconica, sensilla styloconica, or other gustatory chemosensilla from maxillary palps and antenna (Vogt et al, 2002 ), the adult expression of BmorGOBP2 was shown to be associated with the female moth pheromone gland (Xuan et al, 2014 ), strongly suggesting multiple functions for this protein. Gel digestion of SDS-PAGE-separated proteins and liquid chromatography coupled to tandem mass spectrometry (Nano-LC/MS/MS) analysis showed the presence of GOBP2 with many other OBPs (OBP6, OBP56d, PBP-related protein 3, sericotropin, and protein B1) in a library of more than 9,000 peptides from the Bombyx pheromone gland (Xuan et al, 2014 ), urging us to use molecular biology and quantitative real-time PCR as an alternative/complementary approach of biochemistry and immunoblotting to focus on the PBP/GOBP clade.…”

Comparative Genomics Provide Insights Into Function and Evolution of Odorant Binding Proteins in Cydia pomonella

“…The purifying selection of OBP genes is potentially due to functional constraints (Gong D. P. et al, 2009). However, among the OBP genes of lepidopteran species, the major function of PBPs is mainly to sense pheromones (Gong Y. et al, 2009), while GOBPs mainly sense the volatiles of host plants (Vogt et al, 2002). We assumed that GOBP/PBP genes may evolve under positive selection due to the vast diversity of sex pheromones and host volatiles.…”

OBP14 (Odorant-Binding Protein) Sensing in Adelphocoris lineolatus Based on Peptide Nucleic Acid and Graphene Oxide

“…The ability of OBP proteins to bind and solubilize small hydrophobic compounds can be adapted to a variety of roles in biological systems. In other words, the distinct tissue-biased distribution of OBP genes in insects is related to distinct biological functions [32][33][34][35]. Hence, detection of the expression of OBP genes in insects is central to questions concerning the biological functions of OBP genes.…”