Abstract
The fruit fly Drosophila melanogaster and its endoparasitoid wasps are a developing model system for interactions between host immune responses and parasite virulence mechanisms. In this system, wasps use diverse venom cocktails to suppress the conserved fly cellular encapsulation response. Although numerous genetic tools allow detailed characterization of fly immune genes, lack of wasp genomic information has hindered characterization of the parasite side of the interaction. Here, we use high-throughput nucleic acid and amino acid sequencing methods to describe the venoms of two related Drosophila endoparasitoids with distinct infection strategies, Leptopilina boulardi and L. heterotoma. Using RNA-seq, we assembled and quantified libraries of transcript sequences from female wasp abdomens. Next, we used mass spectrometry to sequence peptides derived from dissected venom gland lumens. We then mapped the peptide spectral data against the abdomen transcriptomes to identify a set of putative venom genes for each wasp species. Our approach captured the three venom genes previously characterized in L. boulardi by traditional cDNA cloning methods as well as numerous new venom genes that were subsequently validated by a combination of RT-PCR, blast comparisons, and secretion signal sequence search. Overall, 129 proteins were found to comprise L. boulardi venom and 176 proteins were found to comprise L. heterotoma venom. We found significant overlap in L. boulardi and L. heterotoma venom composition but also distinct differences that may underlie their unique infection strategies. Our joint transcriptomic-proteomic approach for endoparasitoid wasp venoms is generally applicable to identification of functional protein subsets from any non-genome sequenced organism.
Highlights
The fruit fly Drosophila melanogaster is a genetic model system that has been important in the study of conserved aspects of host innate immune responses against pathogens [1]
We considered transcript sequences that were hit by more than one of the filtered venom peptides to code for genuine venom proteins, and this analysis yielded 129 putative venom proteins for L. boulardi and 176 venom proteins for L. heterotoma (Datasets S1–S4)
Our approach integrated high-throughput transcriptomic and proteomic data to investigate the venoms of two endoparasitoid wasp species, L. boulardi and L. heterotoma
Summary
The fruit fly Drosophila melanogaster is a genetic model system that has been important in the study of conserved aspects of host innate immune responses against pathogens [1]. Some of the most common pathogens of fruit flies are endoparasitoid wasps, which can infect greater than 50% of flies in natural populations [9,10,11]. These wasps lay their eggs in fruit fly larvae and pupae, and the developing wasp larvae eventually consume and kill their fly hosts. Given the genetic tools available in D. melanogaster, the identification of venoms from Drosophila endoparasitoids would allow for detailed studies on the molecular biology and evolution of interacting host immune proteins and parasite virulence proteins
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