V-ATPase E mediates Cry2Ab binding and toxicity in Helicoverpa armigera

Area of Science:

• Agricultural Entomology
• Molecular Biology
• Biochemistry

Background:

• Bacillus thuringiensis (Bt) Cry2Ab protein offers an alternative for managing insect pests resistant to Cry1A toxins.
• Vacuolar H+-ATPase subunits A and B (V-ATPase A and B) have been implicated in Bt protein insecticidal activity.

Purpose of the Study:

• To investigate the role of V-ATPases subunit E in Cry2Ab toxicity in Helicoverpa armigera.
• To identify V-ATPases E as a potential receptor for Cry2Ab.

Main Methods:

• RT-PCR to analyze gene expression changes in H. armigera larvae exposed to Cry2Ab.
• Ligand blot, homologous, and heterologous competition assays to confirm protein binding.
• Heterologous expression in Sf9 cells and gene knockdown in H. zea midgut cells to assess functional roles.
• In vivo bioassays with H. armigera larvae.

Main Results:

• Cry2Ab exposure significantly reduced H. armigera V-ATPase E (HaV-ATPase E) expression.
• HaV-ATPase E physically and specifically bound to activated Cry2Ab toxin.
• Enhanced Cry2Ab susceptibility in Sf9 cells expressing HaV-ATPase E.
• Decreased Cry2Ab cytotoxicity in H. zea cells with reduced V-ATPase E.
• Increased H. armigera larval mortality when fed Cry2Ab with HaV-ATPase E protein.

Conclusions:

• V-ATPases E is a putative receptor for Cry2Ab in H. armigera.
• V-ATPases E can enhance Cry2Ab toxicity.
• Targeting V-ATPases E may provide a strategy to manage Cry2Ab resistance in insect pests.