Proteo-trancriptomic analyses reveal a large expansion of metalloprotease-like proteins in atypical venom vesicles of the wasp Meteorus pulchricornis (Braconidae)

Open Access Journal; Published online: 19 Jul 2021Meteorus pulchricornis (Ichneumonoidea, Braconidae) is an endoparasitoid wasp of lepidopteran caterpillars. Its parasitic success relies on vesicles (named M. pulchricornis Virus-Like Particles or MpVLPs) that are synthesized in the venom gland and injected into the parasitoid host along with the venom during oviposition. In order to define the content and understand the biogenesis of these atypical vesicles, we performed a transcriptome analysis of the venom gland and a proteomic analysis of the venom and purified MpVLPs. About half of the MpVLPs and soluble venom proteins identified were unknown and no similarity with any known viral sequence was found. However, MpVLPs contained a large number of proteins labelled as metalloproteinases while the most abundant protein family in the soluble venom was that of proteins containing the Domain of Unknown Function DUF-4803. The high number of these proteins identified suggests that a large expansion of these two protein families occurred in M. pulchricornis. Therefore, although the exact mechanism of MpVLPs formation remains to be elucidated, these vesicles appear to be “metalloproteinase bombs” that may have several physiological roles in the host including modifying the functions of its immune cells. The role of DUF4803 proteins, also present in the venom of other braconids, remains to be clarified

High Hemocyte Load Is Associated with Increased Resistance against Parasitoids in Drosophila suzukii, a Relative of D. melanogaster

Among the most common parasites of Drosophila in nature are parasitoid wasps, which lay their eggs in fly larvae and pupae. D. melanogaster larvae can mount a cellular immune response against wasp eggs, but female wasps inject venom along with their eggs to block this immune response. Genetic variation in flies for immune resistance against wasps and genetic variation in wasps for virulence against flies largely determines the outcome of any fly-wasp interaction. Interestingly, up to 90% of the variation in fly resistance against wasp parasitism has been linked to a very simple mechanism: flies with increased constitutive blood cell (hemocyte) production are more resistant. However, this relationship has not been tested for Drosophila hosts outside of the melanogaster subgroup, nor has it been tested across a diversity of parasitoid wasp species and strains. We compared hemocyte levels in two fly species from different subgroups, D. melanogaster and D. suzukii, and found that D. suzukii constitutively produces up to five times more hemocytes than D. melanogaster. Using a panel of 24 parasitoid wasp strains representing fifteen species, four families, and multiple virulence strategies, we found that D. suzukii was significantly more resistant to wasp parasitism than D. melanogaster. Thus, our data suggest that the relationship between hemocyte production and wasp resistance is general. However, at least one sympatric wasp species was a highly successful infector of D. suzukii, suggesting specialists can overcome the general resistance afforded to hosts by excessive hemocyte production. Given that D. suzukii is an emerging agricultural pest, identification of the few parasitoid wasps that successfully infect D. suzukii may have value for biocontrol

Genetic interactions between the parasitoid wasp Leptopilina boulardi and its Drosophila hosts.

International audienc

Testing the unique amplification event and the worldwide migration hypothesis of insecticide resistance genes with sequence data

International audienceIn the mosquito Culex pipiens, over-production of esterases is a common insecticide resistance mechanism. Different alleles at the esterase A and B loci are known to occur in natural populations, as shown by enzyme electrophoresis and RFLP studies on the esterase B locus. Here we analyse the variability of the esterase A locus at the nucleotide level in mosquitoes possessing or lacking over-produced esterase A. A surprisingly high level of nucleotide polymorphism is found in coding and noncoding regions, and the extent of polymorphism detected is higher than that previously described for the most polymorphic loci in Drosophila. We also show that eight strains from different localities (Africa, America, Asia) that possess the over-produced esterase A2 share the same nucleotide sequence at the esterase A locus, strongly supporting the evolutionary scenario of a unique event of amplification of this gene followed by dispersal through migration rather than the occurrence of multiple independent mutational events of the gene