Identification of olfactory genes of a forensically important blow fly, Aldrichina grahami (Diptera: Calliphoridae)

Abstract

Background The time-length between the first colonization of necrophagous insect on the corpse and the beginning of investigation represents the most important forensic concept of minimum post-mortem inference (PMImin). Before colonization, the time spent by an insect to detect and locate a corpse could significantly influence the PMImin estimation. The olfactory system plays an important role in insect food foraging behavior. Proteins like odorant binding proteins (OBPs), chemosensory proteins (CSPs), odorant receptors (ORs), ionotropic receptors (IRs) and sensory neuron membrane proteins (SNMPs) represent the most important parts of this system. Exploration of the above genes and their necrophagous products should facilitate not only the understanding of their roles in forging but also their influence on the period before PMImin. Transcriptome sequencing has been wildly utilized to reveal the expression of particular genes under different temporal and spatial condition in a high throughput way. In this study, transcriptomic study was implemented on antennae of adult Aldrichina grahami (Aldrich) (Diptera: Calliphoridae), a necrophagous insect with forensic significance, to reveal the composition and expression feature of OBPs, CSPs, ORs, IRs and SNMPs genes at transcriptome level. Method Antennae transcriptome sequencing of A. grahami was performed using next-generation deep sequencing on the platform of BGISEQ-500. The raw data were deposited into NCBI (PRJNA513084). All the transcripts were functionally annotated using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Differentially expressed genes (DEGs) were analyzed between female and male antennae. The transcripts of OBPs, CSPs, ORs, IRs and SNMPs were identified based on sequence feature. Phylogenetic development of olfactory genes of A. grahami with other species was analyzed using MEGA 5.0. RT-qPCR was utilized to verify gene expression generated from the transcriptome sequencing. Results In total, 14,193 genes were annotated in the antennae transcriptome based on the GO and the KEGG databases. We found that 740 DEGs were differently expressed between female and male antennae. Among those, 195 transcripts were annotated as candidate olfactory genes then checked by sequence feature. Of these, 27 OBPs, one CSPs, 49 ORs, six IRs and two SNMPs were finally identified in antennae of A. grahami. Phylogenetic development suggested that some olfactory genes may play a role in food forging, perception of pheromone and decomposing odors. Conclusion Overall, our results suggest the existence of gender and spatial expression differences in olfactory genes from antennae of A. grahami. Such differences are likely to greatly influence insect behavior around a corpse. In addition, candidate olfactory genes with predicted function provide valuable information for further studies of the molecular mechanisms of olfactory detection of forensically important fly species and thus deepen our understanding of the period before PMImin.

Identification of candidate chemosensory genes in Bactrocera cucurbitae based on antennal transcriptome analysis

“…The ability of an insect to recognise odours relies heavily on their OBPs ( Barbosa et al, 2018 ), as these small, water-soluble proteins facilitate the transport of odour molecules through the sensory lymph and serve as connections between external environmental stimuli and odour receptors ( Pelosi et al, 2006 ; Leal, 2013 ; Han et al, 2020 ). In this study, 35 candidate OBPs were identified in the antennal transcriptome of B. cucurbitae .…”

Identification of candidate chemosensory genes in Bactrocera cucurbitae based on antennal transcriptome analysis

“…The ability of an insect to recognize odours relies heavily on their OBPs (Barbosa et al, 2018), as these small, water-soluble proteins facilitate the transport of odour molecules through the sensory lymph and serve as connections between external environmental stimuli and odour receptors (Han et al, 2020;Leal, 2013;Pelosi et al, 2006)…”

“…2). Information including the unigene reference, length, and best Blastx hit for all 35 OBPs is listed in Table 1.…”

Antennal transcriptome analysis reveals sensory receptors potentially associated with host detection in the livestock pest Lucilia cuprina

“…Finding suitable hosts for oviposition is primarily guided by olfactory stimuli [ 16 , 19 ]. Once a host is selected, females use receptors associated with the labellum, tarsi and ovipositor to select an oviposition site which will provide the larvae with enough food to complete their development [ 23 – 25 ]. In blowflies (as in other insects), chemical compounds from the surrounding environment enter the fly's body through porous sensilla located in the cuticle [ 26 ].…”

“…Different sensory receptors have been identified in blowflies, namely, membrane receptors such as odorant receptors (ORs), gustatory receptors (GRs) and ionotropic receptors (IRs) [ 25 , 27 – 29 ], and odor-molecule carriers, including chemosensory proteins (CSPs), odorant-binding proteins (OBPs) and CD36-sensory neuron membrane proteins (CD36/SNMPs) [ 25 , 27 – 30 ]. However, beyond these descriptive works, there is no functional information on these receptors in Calliphoridae.…”