2007 Annual Report
1a.Objectives (from AD-416)
Make publicly available a predictive computer program for mycotoxin levels in Midwest corn and adapt as necessary for a wider range of human food use corn varieties. Use molecular biological approaches to discover, introduce, and evaluate new insect resistance genes (producing bioactive proteins and secondary metabolites), alone and in combination. Use molecular biological approaches to discover, introduce, and evaluate plant-derived selectable markers for transgenic plant production.
1b.Approach (from AD-416)
As part of the process of making the program publicly available, feedback on the present state of the program will be sought and utilized as appropriate. An electronic module to assist in making control decisions will be developed and incorporated. The program will be tested for utility in food grade corn by comparing actual field collected data with predicted levels and correcting as necessary empirically. Genes identified in the prior project that are potentially useful in combination will be examined in model systems and further evaluated. New genes of potential use will be identified through functional targeting of cDNA, array-based technology. Molecular evolution of genes coding for resistance proteins will be utilized to further optimize efficacy against insects, while at the same time minimizing vertebrate effects. Gene product efficacy will be examined in model systems and in regenerated corn. Plant-derived genes involved in toxin resistance will be the ultimate focus of the investigation, although genes from other sources will initially be examined if appropriate plant-derived gene sequence information is not yet sufficient for cloning. Efficacy of target gene products as selectable markers and against insects, alone and in combination with insect-active genes, will be investigated.
Additional data collected for validation of the predictive computer program, including from several popcorn fields. Damage of corn expressing a thale cress derived potential insect-resistance protein was found to be inversely correlated to amounts of the protein produced. Some corn tissues that expressed an introduced gene involved in pigment production had enhanced resistance to insects compared to corresponding tissues that did not express the gene. Further molecular evolutionary refinement of a protein with activity against insects resulted in a product that killed a greater number of insects than the original protein. Some plants that had a version of the gene introduced had enhanced resistance to insect pests. Active extracts, some subfractionated, were isolated from a petunia, palm, and sedge species with resistance to insect pests. When a gene responsible for producing a mutant protein in corn was expressed in corn callus, the callus was less sensitive to a selecting agent than callus that did not contain the gene. Genomic searches involving conserved sequences of three genes often involved in insect and disease resistance indicated several to a few dozen gene/allele forms of each are present in switchgrass. Experiments with greenhouse-grown switchgrass indicated both intra- and inter-varietal differences in resistance to armyworms.
Expression of new plant-derived gene significantly reduces insect damage in corn. Insect damage and associated ear-mold toxins cause hundreds of millions of dollars in losses each year. ARS scientists evaluated three different lines of corn tissue and plants engineered to produce a thale cress protein that potentially degrades the skin of insects. Some transformants killed most of the insects tested, and feeding damage by insects was inversely correlated to the amount of protein produced. Expression of the protein is a potentially useful method for developing an effective combination of naturally derived plant-resistance traits to insects, thereby reducing the ear mold toxins and improving the health of animals and people, and increasing the exportability of U.S. corn. This research addresses National Program 108, Component 2, Mycotoxins and Plant Toxins; Problem Statement 2.1.2 Crop/Fungal/Toxin Relationships.
5.Significant Activities that Support Special Target Populations
A predictive computer program used as part of an ear mold toxin (mycotoxin) management program with representative farmers from a 200 farmer organization again provided useful predictions of fumonisin and aflatoxin levels for corn (including popcorn) in 2006, predicting values close to those actually encountered. Once made widely available, this computer program should allow farmers to more economically produce larger amounts of healthier, high-quality corn with reduced levels of mycotoxins. This higher quality product should help the farmers increase sales and help livestock productivity of farmers using corn for on-farm animal feed.
|Number of non-peer reviewed presentations and proceedings||8|
|Number of newspaper articles and other presentations for non-science audiences||2|
Dowd, P.F., Johnson, E.T., Pinkerton, T.S. 2007. Oral toxicity of beta-N-acetyl hexosaminidase to insects. Journal of Agricultural and Food Chemistry. 55(9):3421-3428.
Johnson, E.T., Berhow, M.A., Dowd, P.F. 2007. Expression of a maize Myb transcription factor driven by a putative silk-specific promoter significantly enhances resistance to Helicoverpa zea in transgenic maize. Journal of Agricultural and Food Chemistry. 55(8):2998-3003.