Aphidius ervi venom regulates Buchnera contribution to host nutritional suitability

Area of Science:

• Insect molecular biology
• Chemical ecology
• Symbiosis research

Background:

• The pea aphid-parasitoid wasp interaction is a model for host-symbiont-parasitoid dynamics.
• Aphidius ervi venom contains Ae-γ-glutamyl transpeptidase (Ae-γ-GT), known to cause host castration.
• Understanding venom's molecular mechanisms is crucial for insect interaction studies.

Purpose of the Study:

• Investigate the in vivo functional role of Ae-γ-GT in the pea aphid-parasitoid system.
• Determine Ae-γ-GT's effect on host ovary degeneration and symbiont load.
• Elucidate Ae-γ-GT's role in balancing venom components and host regulation.

Main Methods:

• Double-stranded RNA microinjections into Aphidius ervi pupae to knock down Ae-γ-GT1 and Ae-γ-GT2 genes.
• Assessing phenotypic changes in parasitized pea aphids and parasitoid progeny using venom lacking Ae-γ-GT.
• Quantifying Buchnera aphidicola symbiont load in hosts and parasitoids.

Main Results:

• Ae-γ-GT gene silencing in parasitoids led to enhanced growth in both hosts and parasitoids.
• A higher load of Buchnera aphidicola symbionts was observed following Ae-γ-GT knockdown.
• Emerging parasitoid adults exhibited reduced survival and fecundity, correlating with increased body size.

Conclusions:

• Ae-γ-GT plays a primary role in inducing host ovary degeneration.
• Ae-γ-GT counterbalances Buchnera aphidicola proliferation, likely triggered by other venom components.
• This study offers novel insights into aphid parasitoid venom function and host regulation.