Galectins in Bti tolerance and resistance in the mosquito Aedes aegypti

University Of Missouri Kansas City, Kansas City MO

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Abstract

? DESCRIPTION (provided by applicant): Dengue viruses (DENV) are primarily transmitted by the mosquito Aedes aegypti, and no effective vaccines and treatments are currently available for dengue fever. Mosquito control using chemical insecticides and by bednets is still a main strategy for controlling of vector-borne diseases. However, massive application of chemical insecticides has caused pollutions to environment and resulted in insecticide-resistance. Bacillus thuringiensis (Bt) is a spore-forming Gram-positive bacterium, and it produces crystal-like parasporal inclusions consisting of Cry toxins that are specifically toxic to insects. Toxins produced by B. thuringiensis subsp. israelensis (Bti) are toxic to several species of mosquitoes and have been widely used for mosquito control. Bt resistance has been correlated with low expressions or alterations of the Cry toxin receptors. Our preliminary results showed that RNAi knockdown of galectin-14 in A. aegypti significantly decreased mosquito survival after treating with Bti toxins, while feeding mosquitoes with recombinant galectin-14 significantly increased mosquito survival, and galectin-14 could interact with alkaline phosphatase 1 (ALP1), one of the putative receptors for Cry11A. Therefore, we hypothesize that galectins may directly interact with putative Cry toxin receptors to block Cry toxins from binding to toxin receptors, resulting in alteration of toxin tolerance and resistance. The long-term goal of this research is to identify an then target galectins by RNAi or chemicals, so that galectins will not interfere with Cry toxin binding and thus making mosquitoes more susceptible to Bti toxins for mosquito control. In this application, we will first characterize galectin-14 and study the roles of other four galectins tha are also highly expressed in A. aegypti larvae in Bti tolerance and resistance (Aim 1) by RNAi knockdown expression of galectins, antibody neutralization of galectins and feeding with recombinant galectins, and then use galectin-14 as a proto-type galectin to investigate the mechanisms of galectins in Bti tolerance/resistance (Aim 2) by protein-protein interactions among galectin-14, Cry11A and putative Cry toxin receptors (cadherin, ALP and APN) using protein pull-down, plate ELISA and Surface Plasmon Resonance (SPR) assays.