D3351: Nanobodies as synergists of insecticidal proteins from Bacillus thuringiensis

The insecticidal Cry proteins from the bacterium Bacillus thuringiensis are active ingredients in biopesticides and produced by transgenic crops to control lepidopteran larvae. These insecticidal proteins induce toxicity by interacting with gut membrane receptors and forming oligomers capable of pore formation on the membrane of midgut cells in the host. Interactions with midgut receptors drives the high specificity displayed by Cry proteins. On the other hand, potentiation of Cry toxicity would help expand range of activity to new insect pest targets and provide a more effective “higher dose” in transgenic crops vital to delay resistance emergence. Recombinant protein receptor fragments were previously shown to increase insect susceptibility to Cry proteins by promoting oligomerization or increasing protection against the gut fluid proteases. Here, we present the design of a nanobody-based strategy by which bispecific nanobodies target Cry proteins to new receptors and enhance Cry toxicity in the fall armyworm (Spodoptera frugiperda) and the corn earworm (Helicoverpa zea). While results support the potential for these nanobodies in agricultural and pest management practices, further research is needed to characterize their mode of action.