Pre-feeding of a glycolipid binding protein LEC-8 from Caenorhabditis elegans revealed enhanced tolerance to Cry1Ac toxin in Helicoverpa armigera

Abstract

Crystal toxins from Bacillus thuringiensis bind to glycolipids and glycoproteins using two different lectin domains in the toxin protein. Our previous observations suggested that the sequestration of crystal toxin depends on the functional interaction of a toxin lectin with glycolipids. Given the finding that competition of a galectin LEC-8 with Cry5B for binding to glycolipids resulting in reduced Bt toxicity in nematode, it is interesting to explore the role of LEC-8 in insects. Here, we reported that the LEC-8 can also be exploited by insect for their survival when they were fed with Bt toxin food. Bioassay with LEC-8 showed that pre-feeding of Helicoverpa armigera larvae reduced the Cry1Ac susceptibility. Both LEC-8 and Cry1Ac bind to the midgut glycolipid in a similar way. Further ELISA indicated that LEC-8 interacts with glycolipid from insect midgut, thus reduce Cry1Ac binding to glycolipid. This in turn enhances insect tolerance to Cry1Ac toxin. The sugar determinants of LEC-8 were studied by using haemagglutination (HA) and haemagglutination inhibition (HAI) assay. It was suggested that the terminal sugar of LEC-8 has multiple sugar binding property.