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Title: A Western Corn Rootworm Cadherin-like Protein is not Involved in the Binding and Toxicity of Cry34/35Ab1 and Cry3Aa Bacillus Thuringiensis Proteins

Author
item TAN, S - Dow Agro Sciences
item JURZENSKI, J - University Of Nebraska
item HASLER, J - Dow Agro Sciences
item Chen, Hong
item WANG, H - University Of Nebraska
item SIEGFRIED, B - University Of Nebraska

Submitted to: Entomological Society of America Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/3/2013
Publication Date: N/A
Citation: N/A

Interpretive Summary: Corn rootworms can be devastating pest to corn producers in the 'corn-belt'. With the development of genetically modified corn, called Bt corn, seed companies have provided for approximately 20 years a product to corn producers that resisted many insect pests including corn rootworms. And with Bt corn, virtually no insecticides were needed; this was very positive for the overall ecology of the agronomic areas. The development of resistance to Bt crops is a major concern to the seed industry, crop producers, and academics. Identification of Bt-toxin receptor(s) in a target insect is essential to understand the mechanism of the insect resistance to Bt crop and to prevent or otherwise counteract the resistance. The key receptor of the Bt toxin as reported in other species of beetles is not a key receptor of the Bt toxins in the rootworm as revealed by this study.

Technical Abstract: The western corn rootworm (WCR) Diabrotica virgifera virgifera LeConte is an important insect pest of corn. Bacillus thuringiensis (Bt) insecticidal proteins Cry3Aa (as mCry3A) and Cry34Ab1/Cry35Ab1 have been expressed in transgenic corn and are used to control the insect in the U.S. To date, there is limited information regarding the target sites for these proteins. In this study, a cadherin-like gene associated with the WCR larval midgut tissue was tested (GenBank accession # EF531715). Experiments were designed: (1) to examine the sensitivity of WCR to Cry34Ab1/35Ab1 and Cry3Aa after silencing the expression of the candidate receptor protein, cadherin, through RNA interference on overlay artificial diet bioassay, and (2) to determine whether Bt proteins bind to recombinant rootworm cadherin protein using ligand blots. The mortality and growth inhibition of WCR neonates exposed to cadherin dsRNA for 2 days followed by either Cry3Aa or Cry34Ab1/Cry35Ab1 for 4 days were comparable to the results observed in insect exposure to either Cry3Aa or Cry34Ab1/Cry35Ab1 treatment alone, even though quantitative real-time PCR confirmed the dsRNA knockdown of cadherin expression in the larvae. In addition, ligand blots of recombinant cadherin protein probed with Cry proteins did not reveal binding with the rootworm-active Cry proteins. These data indicate that the WCR cadherin is unlikely to be involved in the toxicity and binding of Cry34/35Ab1 and Cry3Aa.