Mechanism of Galectin 8 protein in Aedes aegypti to survive Bt Cry11Aa

Abstract Aedes aegypti is a crucial vector of many diseases that cause millions of deaths worldwide. Cry11Aa display high toxicity to the larvae of Ae.aegypti. And the Galectins are a family of β-galactoside binding proteins that play a role in immune responses and may also affect Cry11Aa toxin activity. In our previous work, Galectin 6 and Galectin 14 were found to affect toxicity of Bt toxins. However, there are also some other galectin genes expressed in the gut of Ae.aegypti, such as Galectin 8, whose function is still not confirmed yet. In order to further understand its function and molecular mechanism, Ae.aegypti galectin 8 gene was cloned, expressed the recombinant protein and purified in this study. The bioassays results indicated that Galectin 8 is similar to Galectin 6 to reduce the toxicity of Cry11Aa. In order to determine interactions among Galectin8, Cry11Aa and toxin receptors, Octet Red System, Western blot, far-western blot assay were also performed. Octet Red System result showed that Galectin 8 could also bind to BBMVs of Ae.aegypti, but the kDa value is smaller than that of Galectin 6, indicating that Galectin 8 had a stronger binding ability to BBMVs than Galectin 6. Western blot and far-western blot analyses also demonstrated that Galectin 8 could bind to Ae.aegypti receptor ALP1 and APN2, similar to result of protein docking simulation. All of these results support the conclusion that Galectin 8 may increase block Cry11Aa from binding to ALP1 and APN2 than Galectin 6, which might decrease the toxicity of Cry11Aa for Ae.aegypti.