Abstract
Parasitoid wasps rely primarily on venom to suppress the immune response and regulate the physiology of their host. Intraspecific variability of venom protein composition has been documented in some species, but its evolutionary potential is poorly understood. We performed an experimental evolution initiated with the crosses of two lines of Leptopilina boulardi of different venom composition to generate variability and create new combinations of venom factors. The offspring were maintained for 10 generations on two strains of Drosophila melanogaster differing in resistance/susceptibility to the parental parasitoid lines. The venom composition of individuals was characterized by a semi-automatic analysis of 1D SDS-PAGE electrophoresis protein profiles whose accuracy was checked by Western blot analysis of well-characterized venom proteins. Results made evident a rapid and differential evolution of the venom composition on both hosts and showed that the proteins beneficial on one host can be costly on the other. Overall, we demonstrated the capacity of rapid evolution of the venom composition in parasitoid wasps, important regulators of arthropod populations, suggesting a potential for adaptation to new hosts. Our approach also proved relevant in identifying, among the diversity of venom proteins, those possibly involved in parasitism success and whose role deserves to be deepened.
Highlights
The question of the adaptive evolution of venom composition has been mainly studied in predatory venomous animals, with evidence for natural selection generally driven by diet (e.g., [1,2,3]) and by environmental conditions [4]
This question remainshowever largely unaddressed for parasitoid wasps—insects that develop at the expense of their arthropod host, leading to its death— they rely primarily on the injection of venom during oviposition to overcome the immune defenses of the host and optimize the development of their offspring [8,9]
We observed a rapid and differential evolution of the venom composition on the two host strains, and proteins whose quantity in venom has probably changed under selection were identified
Summary
The question of the adaptive evolution of venom composition has been mainly studied in predatory venomous animals, with evidence for natural selection generally driven by diet (e.g., [1,2,3]) and by environmental conditions [4]. LbGAP is a RhoGAP domain-containing protein seemingly required for parasitism success on the resistant strain of D. melanogaster (see below) through targeting of the host immune cells [13,14,15,16,17] This protein is much more abundant in the ISm venom than LbGAPy in the ISy venom due to a variation in the cis-regulation of the expression of the two alleles [13]. We observed a rapid and differential evolution of the venom composition on the two host strains, and proteins whose quantity in venom has probably changed under selection were identified These are candidates for further functional studies to assess their possible role in parasitism success
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