The mosquito Aedes aegypti is associated with the spread of many viral diseases in humans, including Dengue virus (DENVs), Yellow fever virus (YFV), Zika virus (ZIKV), and Chikungunya virus (CHIKV). Bacillus thuringiensis (Bt) is widely used as a biopesticide, which produces Cry toxins for mosquito control. The Cry toxins bind mainly to important receptors, including alkaline phosphatase (ALP) and aminopeptidase-N (APN). This work investigated the function of a C-type lectin, CTLGA9, in A. aegypti in response to Cry toxins. Our results showed by far-western blot and ELISA methods that the CTLTGA9 protein interacted with brush border membrane vesicles (BBMVs) of A. aegypti larvae and with ALP1, APN, and Cry11Aa proteins. Furthermore, molecular docking showed overlapping binding sites in ALP1 and APN for binding to Cry11Aa and CTLGA9. The toxicity assays further demonstrated that CTLGA9 inhibited the larvicidal activity of Cry toxins. According to the results of molecular docking, CTLGA9 may compete with Cry11Aa for binding to ALP1 and APN receptors and thus decreases the mosquitocidal toxicity of Cry11Aa. Our results provide further insights into better understanding the mechanism of Cry toxins and help improve the Cry toxicity for mosquito control.
Background
Bacillus thuringiensi
s
israelensis
(Bti) is a widely used mosquitocidal microbial pesticide due to its high toxicity. ATP-binding proteins (ABP) are prevalently detected in insects and are related to reaction against Bti toxins. However, the function of ABP in mosquito biocontrol is little known, especially in
Aedes aegypti
. Therefore, this study aimed to clarify the function of ABP in
Ae. aegypti
against Bti toxin.
Results
Aedes aegypti
ABP (GenBank: XM_001661856.2) was cloned, expressed and purified in this study. Far-western blotting and ELISA were also carried out to confirm the interaction between ABP and Cry11Aa. A bioassay of Cry11Aa was performed both in the presence and absence of ABP, which showed that the mortality of
Ae. aegypti
is increased with an increase in ABP.
Conclusions
Our results suggest that ABP in
Ae. aegypti
can modulate the toxicity of Cry11Aa toxin to mosquitoes by binding to Bti toxin. This could not only enrich the mechanism of Bt toxin, but also provide more data for the biocontrol of this transmission vector.
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