Selectable markers with potential activity against insects, plus other insect-oriented strategies for mycotoxin reduction in Midwest corn

Authors: Dowd, Patrick; Johnson, Eric; Pinkerton, Terrence

Submitted to: Multicrop Aflatoxin and Fumonisin Elimination and Fungal Genomics Workshop-The Peanut Foundation
Publication Type: Abstract Only
Publication Acceptance Date: 10/24/2007
Publication Date: 10/27/2007
Citation: Dowd, P.F., Johnson, E.T., Pinkerton, T.S. 2007. Selectable markers with potential activity against insects, plus other insect-oriented strategies for mycotoxin reduction in Midwest corn [abstract]. Multicrop Aflatoxin and Fumonisin Elimination and Fungal Genomics Workshop-The Peanut Foundation. p.117

Interpretive Summary:

Technical Abstract: Reduction of insect damage has the potential to greatly reduce the levels of mycotoxins in corn, as studies with Bt corn have shown. However, the large number of insect species involved necessitates the development of comprehensive insect control to most effectively utilize this strategy. One strategy that we have explored is field-based management, which relies on a predictive computer program that allows farmers to make more informed decisions for applying insect or mold control, including early harvest and drying. The program recently has been converted to a web-based version and is awaiting loading. Additional data has been collected for popcorn to allow expansion to that commodity. The field corn version of the program continues to detect conditions where aflatoxin may result and has done well in predicting fumonisin levels. Our recent progress towards comprehensive insect resistance in corn has included identification of a hexosaminidase which enhanced insect resistance in corn transformants, enhanced anthocyanin production that has increased insect resistance in nongrain tissues, molecularly evolved peptides with enhanced activity against insects, and greatly enhanced efficacy of functionally different multigene combinations in the model plant tobacco. Selectable marker genes that are plant-derived and/or non-microbial antibiotic related have the potential to enhance acceptability of transformed plants. The protein product from the model anti-cell death insect virus Autographa callifornica multiple nucleopolyhedrosis virus (AcMNPV) P35 gene significantly enhanced mortality of fall armyworms to the non-host virus Anticarsia gemmatalis multiple nucleopolyhedrosis virus (AgMNPV) in dietary assays. Some transformed corn lines caused greatly enhanced mortality to corn earworms and fall armyworms; and overall feeding was significantly lower in lines that had the gene introduced compared to those that did not. Fall armyworms fed P35 lines had enhanced mortality to AgMNPV compared to those fed on non-P35 lines. The blue fluorescent mutant bf-1 line of maize putatively has an altered anthranilate synthase gene. We identified a single-point mutation in a bf-1 anthranilate synthase, a subunit mRNA, that caused a leucine-to-proline change at residue 531. This unique change is in the substrate-binding domain, as opposed to other mutations in other plants of this enzyme that have involved the tryptophan binding feedback region. Transgenic maize callus expressing the bf-1 mutant anthranilate synthase was resistant to the inexpensive selecting agent 6-methyl anthranilate. Additionally, feeding by corn earworms and fall armyworms was inversely correlated to the levels of the bf-1 anthranilate synthase produced in regenerated corn plants.