Bacillus thuringiensis Cry1A toxins exert toxicity by multiple pathways in insects.

Area of Science:

• Agricultural Entomology
• Molecular Biology
• Biotechnology

Background:

• Bacillus thuringiensis (Bt) crops are vital for insect pest control.
• Understanding Bt toxin pathways is crucial for sustainable use of this biotechnology.

Purpose of the Study:

• To investigate the roles of midgut cadherin and ABCC2 in Bt toxin pathways.
• To elucidate the molecular mechanisms of Bt toxicity in insects.

Main Methods:

• CRISPR/Cas9 mutagenesis was used to create mutations in the cadherin gene of Trichoplusia ni.
• Assays were performed on T. ni strains with mutations in cadherin and ABCC2 genes using Cry1A and Cry2Ab toxins.

Main Results:

• Cadherin and ABCC2 play independent roles in Cry1A toxin action.
• Bt toxins exhibit insecticidal activity via multiple, redundant pathways.
• An additional major pathway for Cry1Aa toxicity was identified, independent of cadherin and ABCC2.
• Cry2Ab toxicity does not involve cadherin or ABCC2.

Conclusions:

• Bt toxins act through a complex network of multiple, redundant pathways.
• This clarifies the molecular modes of action and insect resistance mechanisms to Bt toxins.