Location: Plant Genetics Research2012 Annual Report
1a. Objectives (from AD-416):
1) To develop soybeans with altered seed coat color to facilitate the segregation and identify preservation of seeds with genetically enhanced compositional traits. 2) To produce soybeans with enhanced food, feed, and industrial properties by modification of the oil and lipid-soluble antioxidant composition of seeds. 3) To introduce genes into soybeans that result in high-level accumulation of foreign and engineered proteins valuable for food, feed, and industrial uses. 4) To develop procedures and methods for analyzing and predicting seed protein allergenicity in food and feed. To develop non-allergenic seeds by supressing intrinsic allergens and to modify proteins that are potential transgenes for improving biosafety.
1b. Approach (from AD-416):
1) Co-transformation of soybean with a seed coat color-conferring transgene and a trait transgene will yield visually distinct seeds with enhanced composition. 2) Identify enzymes that are specialized for the metabolism of unusual fatty acids to produce agronomically-viable soybean seeds. 3) Manipulate protein content of soybean seeds by use of plant promotors and compartmentalization of introduced proteins. 4) Identify and characterize soybean food and feed allergens.
3. Progress Report:
We screened the elemental composition of >30,000 soybean seeds including macronutrients in fertilizer, elements of significance to plant and human health and elements causing agricultural or environmental problems. This system was used to profile soybean seed composition as a function of canopy position within experiments altering the environment. Several elements showed significant differences through the canopy for all of the cultivars and environments, while others were specific for given environments and cultivars. Understanding what causes these differences will give a better understanding of adaptations the plants are making to the environment. Genes important for elemental accumulation were identified by profiling 1500 diverse cultivars. Lines showing extremely high or low levels of Sulfur (S), Phosphate (P), Cadmium (Cd), Manganese (Mn) and Aluminum (Al) have been sent to researchers and breeders studying seed S and P, the response to high Cd and Al soils and Mn deficiency soils respectively. We confirmed 16 seed elemental composition mutants identified from a genetic screen to be used to identify the genes under field-grown conditions. The results were used to design a screening strategy that will require 50% fewer samples to perform. We profiled a mapping population derived from soybean cultivars that differ in iron availability and identified several genetic loci affecting seed composition. This will allow identification of important genes for improving yield with less fertilizer or on low quality soils. To explore the metabolism of developing soybean seeds scientists in St Louis, MO previously developed an embryo culturing method which has been used to quantify oil, protein, and carbohydrate levels in seeds that were exposed to different concentrations of sugars and amino acids recorded as a ratio of carbon to nitrogen. These environmental perturbations caused drastic changes in protein levels and altered the fluxes through primary metabolism. These investigators fed a subset of cultures with 13C-isotopes (i.e. amino acids and sugars) and developed methods to assess the label incorporation as a result of metabolism. Radiolabeling experiments were used to monitor differences in carbon allocation. Flux maps were built to better understand the changes in metabolism that can guide rational metabolic engineering efforts. Metabolic events take place dynamically (in time) and occur in distinct locations (cellular and subcellular compartmentation) and limit computational systems biology approaches. Scientists in St. Louis, MO labeled developing seeds with 13C isotopes provided as sugars and amino acids. They used this biomass to develop a method to resolve the labeling in different proteins with mass spectrometry. Current investigations focus on developing improved methods that may allow examination of protein turnover and other temporal events. Together, these investigations provide advanced levels of detail on metabolism that are critical to understanding plant biology and function at molecular levels.
Zhao, J., Wang, C., Welti, R., Bedair, M., Sumner, L., Baxter, I.R., Wang, X. 2011. Suppression of phospholipase D,gammas confers increased aluminum resistance in Arabidopsis thaliana. PLoS One. 6(12):e28086. Available: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0028086.