Abstract
Simple SummaryThe insect chemosensory system is crucial in regulating insect behaviors. Chemosensory proteins (CSPs) are a family of small, soluble proteins conventionally known to transport odorant molecules in insect chemosensory system. Besides chemosensation, CSPs have been reported to play important roles in development, nutrient metabolism, and insecticide resistance. Therefore, identification and characterization of previously unknown CSPs will be valuable for further investigation of this protein family. The cotton bollworm, Helicoverpa armigera (Hübner) is among the most serious insect pests in various agricultural and horticultural crops. In this study, 27 CSP genes were identified from H. armigera genome and transcriptome sequences, and their expression patterns were further examined by using transcriptomic data obtained from different tissues and stages. The results demonstrate that H. armigera CSP genes are highly expressed in both chemosensory and non-chemosensory tissues. Moreover, a new recombinant expression method was developed that can significantly increase H. armigera CSP expression levels as soluble proteins in Escherichia coli. This study improves our understanding of insect CSPs and developed a new approach to highly express recombinant CSPs, which can be expanded to examine CSPs in other species for functional characterization.Chemosensory proteins (CSPs) are a family of small, soluble proteins that play a crucial role in transporting odorant and pheromone molecules in the insect chemosensory system. Recent studies reveal that they also function in development, nutrient metabolism and insecticide resistance. In-depth and systematic characterization of previously unknown CSPs will be valuable to investigate more detailed functionalities of this protein family. Here, we identified 27 CSP genes from the genome and transcriptome sequences of cotton bollworm, Helicoverpa armigera (Hübner). The expression patterns of these genes were studied by using transcriptomic data obtained from different tissues and stages. The results demonstrate that H. armigera CSP genes are not only highly expressed in chemosensory tissues, such as antennae, mouthparts, and tarsi, but also in the salivary glands, cuticle epidermis, and hind gut. HarmCSP6 and 22 were selected as candidate CSPs for expression in Escherichia coli and purification. A new method was developed that significantly increased the HarmCSP6 and 22 expression levels as soluble recombinant proteins for purification. This study advances our understanding of insect CSPs and provides a new approach to highly express recombinant CSPs in E. coli.
Highlights
A myriad of insect behaviors such as foraging, host-feeding, mating and oviposition [1]are mediated by their chemosensory system
Two classes of proteins are highly expressed in chemosensory tissues, where they help deliver the semiochemicals to the receptors for sensation [5], which are odorant-binding proteins (OBPs) [6] and chemosensory proteins (CSPs) [7]
HarmCSP21 and 22 are identical at both mRNA and amino acid sequence levels, they are at two different genomic locations
Summary
A myriad of insect behaviors such as foraging, host-feeding, mating and oviposition [1]are mediated by their chemosensory system. When hydrophobic semiochemicals reach the aqueous sensillum lymph through the pores on chemosensory sensilla, it is difficult for them to reach the membrane-bound receptors directly due to their lack of solubility. Two classes of proteins are highly expressed in chemosensory tissues, where they help deliver the semiochemicals to the receptors for sensation [5], which are odorant-binding proteins (OBPs) [6] and chemosensory proteins (CSPs) [7]. OBPs are one family of small (14–20 kDa), soluble proteins with six conserved cysteines and are involved in odorant binding and delivery in the sensilla [7,8]. CSPs do not share sequence similarities with OBPs and are characterized by only four conserved cysteines [9,10,11,12]. Only 4 CSPs were identified in D. melanogaster, 6 in Apis mellifera [16], and 20 in Bombyx mori [17], whereas 70 were found in Locusta migratoria [18]
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