2011 Annual Report
1a.Objectives (from AD-416)
1. Determine if unintended effects are produced in transgenic crops, using fruit ripening in tomato as a model system. 1A. Determine if unintended effects are produced in transgenic crops, using gene expression analysis as a monitoring tool. 1B. Determine if unintended effects are produced in the fruit of transgenic crops that affect fruit quality or composition, through metabolomic and proteomic profiling and an examination of agronomic trait performance.
2. Determine if unintended effects are reduced in transgenic plants through the use of promoters with tissue-specific expression.
3. Genetically identify the genes affecting Fe levels and bioavailability in maize seed using maize quantitative genetics and Caco-2 cell culture in vitro digestion assay. Determine Fe levels and bioavailability in genetically engineered maize seed.
1b.Approach (from AD-416)
1) Utilize genomic, metabolomic, proteomic and agronomic approaches to evaluate phenotypic difference between tomatoes. 1A) Utilize natural diversity between tomato cultivars, together with conventional breeding techniques, to capture a reasonable phenotypic range from diverse tomato germplasm. 1B) Utilize RNAi and artificial microRNA gene silencing technologies to adjust RIN gene expression levels and alter fruit ripening. Compare phenotypic effects of transgenes to the range observed with conventional cultivars..
2)Leverage research on fruit specific or ripening stage specific promoter sequences to further tailor the modulation of RIN gene expression in the target tissue. Assess the efficacy of tailored gene modulation on reducing unintended effects via genomic, metabolomic, proteomic and agronomic monitoring.
We started a new aspect of biotechnology risk assessment for FY2011, changing focus from tomatoes to corn. This also reflected a shift in the target trait of interest, where in tomato we examined slow ripening/long shelf storage. Our new trait of interest is iron nutritional quality as a novel, value-added grain quality trait for corn. Iron nutritional quality is determined by a combination of factors, those that control elemental iron accumulation in the grain and also biochemical factors that increase the fraction of iron that is easily digested and absorbed (the “bioavailable” fraction). Much of the year was spent working to optimize new analytical procedures to identify these bioavailability promoting compounds. We also made progress in dissecting the genetic and environmental factors that control elemental iron accumulation in the grain and plant. The 2011 cornfield had a mix of varieties, including those developed by this team with enhanced iron nutritional quality, diverse inbred lines used by many geneticists and breeders, and also current commercial varieties that are in widespread planting across the Northeastern US. We expect that this new set of samples will allow us to better understand the factors that determine iron nutritional quality, but also get a better sense for the range in quality that farmers would actually observe from their 2011 harvests.
Iron-biofortified corn supports robust growth of chickens. Corn does not provide sufficient dietary iron to ensure complete health in people or animals. ARS researchers at th Robert W. Holley Center for Agriculture and Health at Ithaca, NY, developed an experimental corn variety using conventional plant breeding that has enhanced iron nutritional quality. This corn was able to supply all the dietary iron needed to support robust growth in broiler chickens over a 6-week experiment. This discovery may help improve the efficiency of animal agriculture and help reduce iron deficiency in people, which presently affects nearly 2 billion worldwide.
Hoekenga, O., Lung'Aho, M., Tako, E., Kochian, L.V., Glahn, R.P. 2011. Iron biofortification of maize grain. Plant Genetic Resources: Characterization and Utilization. 1-3. Available: http://journals.cambridge.org/
Lung'Aho, M., Mwaniki, A., Szalma, S.J., Hart, J., Rutzke, M., Kochian, L.V., Glahn, R.P., Hoekenga, O. 2011. Genetic and physiological analysis of iron content and bioavailability in maize kernels. PLoS One. 6(6):e20429. DOI:10.1371/journal.pone.0020429.