Molecular and Functional Characterization of Three Odorant-Binding Protein from Periplaneta americana.

Zhao-Qun Li,Ya-Nan Zhang,Peng He,Shuang-Lin Dong,J Joe Hull

doi:10.1371/journal.pone.0170072

Abstract

The American cockroach, Periplaneta americana, is a vector of many pathogenic organisms associated with human diseases. Olfaction plays a crucial role in guiding cockroach behaviors and contributes to their ability to transmit pathogens. Odorant binding proteins (OBPs), abundant in the insect olfactory sensilla, are important for insect olfaction. In this study, three OBP genes, PameOBP1, 2 and 3, were cloned from P. americana. Sequence alignment and phylogenetic analysis revealed that PameOBP1, 2 and 3 belong to the Minus-C OBP, Classic OBP, and Plus-C OBP subfamilies, respectively. Expression pattern and ligand-binding analysis showed that PameOBP1 and 2 were specifically expressed in antennae, and exhibited high binding affinities (Ki < 2 μM) to farnesene, farnesol, 2-tridecanone, and tetradecane, suggesting roles in volatile perception. Conversely, PameOBP3 was ubiquitously expressed in most of the tissues examined at high levels and displayed very weak binding affinities (Ki > 40 μM) for all 87 ligands tested. Our study provides insights into the functional diversity of PameOBP genes and provides some volatiles that can potentially be used in behavioral interference of P. americana.

Highlights

A sophisticated and sensitive olfactory system is crucial for many important insect behaviors, such as feeding, mating, and oviposition
Sequence alignment and phylogenetic analysis revealed that these three PameOBPs belong to different odorant binding proteins (OBPs) subfamilies
PameOBP1 is a member of Minus-C OBP as it contains only four conserved cysteine residues; PameOBP2 is a Classic OBP, with the typical six-cysteine motif; and with 8 conserved cysteine residues, PameOBP3 belongs to the Plus-C OBP subfamily (Figs 1 and 2)

Summary

Introduction

A sophisticated and sensitive olfactory system is crucial for many important insect behaviors, such as feeding, mating, and oviposition. The periphery process of insect olfaction involves interactions between odorants and three major protein classes including soluble binding proteins [1], membrane bound receptors [2], and odorant degrading enzymes [3]. As a key component in insect olfaction, odorant binding proteins (OBPs) are abundant, small, water-soluble proteins found in the sensillar lymph surrounding the sensory dendrite, and are thought to bind and transport odorant molecules through the sensillar lymph to activate odorant receptors [2, 4, 5]. OBPs have been further grouped into four subclasses according to the number of conserved cysteines. Three other subclasses of OBPs (non-classical OBPs) are “Minus-C OBPs” with four conserved cysteines, “Plus-C OBPs” with eight conserved cysteines, and “Atypical OBPs” with more than eight conserved cysteines [7]. When compared with the many reports on Classic OBPs, studies of nonclassical OBPs are rare

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Conclusion