Abstract
BackgroundDeciphering the molecular mechanisms mediating the chemical senses, taste, and smell has been of vital importance for understanding the nature of how insects interact with their chemical environment. Several gene families are implicated in the uptake, recognition, and termination of chemical signaling, including binding proteins, chemosensory receptors and degrading enzymes. The cotton leafworm, Spodoptera littoralis, is a phytophagous pest and current focal species for insect chemical ecology and neuroethology.ResultsWe produced male and female Illumina-based transcriptomes from chemosensory and non-chemosensory tissues of S. littoralis, including the antennae, proboscis, brain and body carcass. We have annotated 306 gene transcripts from eight gene families with known chemosensory function, including 114 novel candidate genes. Odorant receptors responsive to floral compounds are expressed in the proboscis and may play a role in guiding proboscis probing behavior. In both males and females, expression of gene transcripts with known chemosensory function, including odorant receptors and pheromone-binding proteins, has been observed in brain tissue, suggesting internal, non-sensory function for these genes.ConclusionsA well-curated set of annotated gene transcripts with putative chemosensory function is provided. This will serve as a resource for future chemosensory and transcriptomic studies in S. littoralis and closely related species. Collectively, our results expand current understanding of the expression patterns of genes with putative chemosensory function in insect sensory and non-sensory tissues. When coupled with functional data, such as the deorphanization of odorant receptors, the gene expression data can facilitate hypothesis generation, serving as a substrate for future studies.
Highlights
Deciphering the molecular mechanisms mediating the chemical senses, taste, and smell has been of vital importance for understanding the nature of how insects interact with their chemical environment
Annotation of Genes from Chemosensory Gene Families An update to the repertoire of genes from previously described gene families with putative chemosensory function is reported here, with focus on novel genes identified in the Odorant Receptor (OR), Gustatory Receptor (GR), Ionotropic Receptor (IR), Odorant Binding Protein (OBP), Chemosensory Protein (CSP), Carboxyl Esterase (CXE)/CCE, and Cytochrome P450 (CYP) families
SlitSNMP1 displayed relatively higher expression in Discussion We used Illumina-based RNA Sequencing methodology to provide a expanded picture of the expression patterns of several S. littoralis gene families involved in chemosensory processes, namely ORs, GRs, IRs, OBPs, CSPs, CXE/CCEs, CYPs, and Sensory Neuron Membrane Protein (SNMP)
Summary
Deciphering the molecular mechanisms mediating the chemical senses, taste, and smell has been of vital importance for understanding the nature of how insects interact with their chemical environment. At the molecular level the processes of chemosensory detection, which include uptake, reception, and inactivation of stimulus molecules [5], are mediated by a diversity of genes from several functionally interrelated gene families: odorant-binding proteins (OBPs) and chemosensory proteins (CSPs) during stimulus uptake; odorant. Walker et al BMC Genomics (2019) 20:428 receptors (ORs), ionotropic receptors (IRs) and gustatory receptors (GRs) during chemosensory stimulus reception; odorant-degrading enzymes (ODEs) including antennal-expressed carboxylesterase (CXEs) and cytochrome P450s (CYPs) during enzymatic degradation of the odorant molecules [5, 6]. These genes have been characterized primarily for their role in chemosensory processes. The expression of a Drosophila melanogaster GR in the brain has been linked to internal sugar monitoring [9], and the characterization of ORs in the sperm of mosquitos [10] resulted in the proposal of a novel function for insect ORs in sperm chemotaxis
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