Abstract
BackgroundLarvae of the Australian sheep blowfly, Lucilia cuprina, parasitise sheep by feeding on skin excretions, dermal tissue and blood, causing severe damage known as flystrike or myiasis. Recent advances in -omic technologies and bioinformatic data analyses have led to a greater understanding of blowfly biology and should allow the identification of protein families involved in host-parasite interactions and disease. Current literature suggests that proteins of the SCP (Sperm-Coating Protein)/TAPS (Tpx-1/Ag5/PR-1/Sc7) (SCP/TAPS) superfamily play key roles in immune modulation, cross-talk between parasite and host as well as developmental and reproductive processes in parasites.MethodsHere, we employed a bioinformatics workflow to curate the SCP/TAPS protein gene family in L. cuprina. Protein sequence, the presence and number of conserved CAP-domains and phylogeny were used to group identified SCP/TAPS proteins; these were compared to those found in Drosophila melanogaster to make functional predictions. In addition, transcription levels of SCP/TAPS protein-encoding genes were explored in different developmental stages.ResultsA total of 27 genes were identified as belonging to the SCP/TAPS gene family: encoding 26 single-domain proteins each with a single CAP domain and a solitary double-domain protein containing two conserved cysteine-rich secretory protein/antigen 5/pathogenesis related-1 (CAP) domains. Surprisingly, 16 SCP/TAPS predicted proteins formed an extended tandem array spanning a 53 kb region of one genomic region, which was confirmed by MinION long-read sequencing. RNA-seq data indicated that these 16 genes are highly transcribed in all developmental stages (excluding the embryo).ConclusionsFuture work should assess the potential of selected SCP/TAPS proteins as novel targets for the control of L. cuprina and related parasitic flies of major socioeconomic importance.Graphical
Highlights
Larvae of the Australian sheep blowfly, Lucilia cuprina, parasitise sheep by feeding on skin excretions, dermal tissue and blood, causing severe damage known as flystrike or myiasis
We identified the full complement of SCP/TAPS genes and inferred proteins in L. cuprina, studied the structure and organisation of these genes and explored their transcription profiles in different stages/sexes of the fly as a foundation for future investigations of their functional roles and possible potential as intervention targets
Manual curation of SCP/TAPS coding regions was performed by analysing each gene prediction in Integrative Genomics Viewer (IGV) and determining the optimal gene model based on the following criteria: (1) each gene model had to have an open reading frame (ORF) with unambiguous intronexon boundaries supported by RNA-seq expression data; (2) coding regions could not be smaller than 400 bp, in accordance with the minimal length of the cysteine-rich secretory protein/antigen 5/pathogenesis related-1 (CAP) domain (IPRO14044; 150 amino acids); (3) a minimum of five RNA-seq reads had to be mapped to the coding region
Summary
Larvae of the Australian sheep blowfly, Lucilia cuprina, parasitise sheep by feeding on skin excretions, dermal tissue and blood, causing severe damage known as flystrike or myiasis. Previous work [12] eluded to a number of groups of molecules, such as GTPases, gustatory and odorant receptors and serine proteases, some of which could be involved in parasitism (the fly-host interplay) and might be potential intervention targets. One such group is the cysteine-rich secretory protein/antigen 5/pathogenesis related-1 (CAP) or sperm-coating protein/TAPS (Tpx-1/ Ag5/PR-1/Sc7) (SCP/TAP) protein superfamily, typified by a conserved CAP domain (Pfam: PF00188, InterProScan: IPR014044) [13]
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