Introduction

Soybean isoflavones (daidzein, genistein and glycitein and their conjugates) have significant beneficial effects on human health by preventing cancer, lowering blood cholesterol, preventing osteoporosis and promoting vascular health. Animal models have shown that soy products are more effective than isoflavone supplements. Generally high isoflavone intake is beneficial for most humans but evidence is available showing that certain breast cancers are stimulated by isoflavones. Thus developing ways to increase or decrease seed isoflavones to satisfy the needs of different consumer groups should enhance the already accepted value of soybean as an important functional food for humans and increase demand. Attainment of these goals should increase soybean consumption, and improve human health. The altered soybean germplasm will also provide new research tools for studying the effects of soy isoflavones on human health and on plant metabolism and physiology. Manipulating isoflavone levels and composition would also be a significant advancement in agricultural science.

Objective

The objective of this research is to determine the critical combination of environmental and genetic factors that will allow for the production of soybean seeds with high or low isoflavone levels.

Summary of Results

A series of experiments were carried out in the field in the US and France and in controlled conditions in the greenhouse that clearly demonstrated for the first time that high temperatures and water deficiency during seed fill lowered isoflavone levels and changed the composition as well. In addition, analysis of soybean seed samples from the first year of the SOYFACE experiment in Urbana in which the CO2 level was doubled in open air field plots indicates that the elevated CO2 level increases seed isoflavone concentration. In all experiments varietal differences were found.

Impact on Ag Biotechnology

Since we now know how to manipulate isoflavone levels by manipulating the environment during seed fill we can determine which enzymes change in activity either to increase or decrease isoflavones. Then one can use the genes for these enzymes to manipulate the enzyme activities through biotechnology to obtain the desired product. This work has been initiated utilizing genes that are likely to affect the isoflavone biosynthetic pathway.

Impact on Decisions in the Public and Private Sectors

The information that we have generated concerning environmental effects on isoflavones and on varietal differences can be used by farmers and the soyfood industry to predict the isoflavone levels under the weather conditions found during the seed fill in different areas. Specific varieties could also be used to stabilize the isoflavone content and composition.

Future Research

Continued studies are needed to confirm the effects of high CO2 and in addition the effects of the environmental pollutant ozone. More varieties need to be tested under the different water, temperature and CO2 conditions to identify those that do and do not respond as much to these changes. The enzymes that are involved in isoflavone biosynthesis need to be measured in order to identify the controls and then genes for these inserted into soybean to obtain the desired alteration.

Publications Resulting from this Project

Nelson, R., V. Lozovaya, A. Lygin and J. Widholm. 2001. Variations in isoflavones in seeds of domestic and exotic soybean germplasm. Crop Sci Soc. Am. Annual Meeting Abstracts.

Lozovaya, V., O. Zernova, A. Lygin, L. Belova, T. Gorshkova and J. Widholm. 2001. Genetic engineering of phenylpropanoid metabolism. Int. Symp. Signalling Systems of Plant Cells, Moscow, June, p. 85.

Nelson R., A. Lygin, V. Lozovaya, A. Ulanov, and J. Widholm. 2002. Genetic and environmental control of soybean seed isoflavone levels and composition. Soy 2002 The 9 Biennial Conference on Cellular and Molecular Biology Of the Soybean, August 11-14, 2002, Urbana, Il. P511.

Manuscripts in Preparation

Nelson, R., A. Lygin, V. Lozovaya and J. Widholm. 2003. Genetic variation for isoflavone concentration and composition in U.S. cultivars.

Nelson, R., A. Lygin, V. Lozovaya and J. Widhohn. 2003. Genetic variation for isoflavone concentration and composition in exotic germplasm.

Lozovaya, V., A. Lygin, A. Ulanov, J. Dayde, R. Nelson and J. Widholm. 2003. Effect of environmental factors on seed isoflavone level and composition of several soybean cultivars.