|Shannon, J. Grover|
Submitted to: Biomed Central (BMC) Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2010
Publication Date: 6/11/2010
Citation: Gutierrez-Gonzalez, J.J., Wu, X., Gillman, J.D., Lee, J., Zhong, R., Shannon, J., Yu, O., Nguyen, H.T., Sleper, D.A. 2010. Intricate environment-modulated genetic networks control isoflavone accumulation in soybean seeds. Biomed Central (BMC) Plant Biology. 10(1):105. Available: http://www.biomedcentral.com/1471-2229/10/105. Interpretive Summary: Soybean is an important component of many foods and animal feeds. Compounds called isoflavones, a nutritional component of soybean seeds, have long been the focus of soybean breeding efforts due to their known roles in both human health and plant fitness. Unfortunately, efforts to either enhance or reduce the levels of isoflavones have been hampered by the extremely complex nature of the trait and the high level of environmental induced variability. In an attempt to better understand the underlying genetics of isoflavone accumulation, we performed a large scale analysis to identify genomic regions associated with isoflavone accumulation. We identified a number of such regions, which form a complex network controlling seed isoflavone levels. We also noted a strong interaction between these regions, a condition referred to as epistasis. The recent release of the whole genome shotgun sequence for soybean allowed the identification of putative candidate genes for a number of these genomic regions. We have advanced understanding of the genetics which control isoflavone synthesis. This work paves the way for future genetic studies to develop more efficient and effective breeding methods for fine control of soybean seed isoflavone levels.
Technical Abstract: Soybean (Glycine max [L] Merr.) seed isoflavones have long been considered a desirable trait to target in selection programs for their involvement on fitness for humans and the plant per se. However, attempts to modify seed isoflavone content have not always produced the expected results because their genetic basis is polygenic and complex. Undoubtedly, the extreme variability that seed isoflavones display over environments has obscured our understanding of the genetics involved. In this study, a mapping population of RILs with three replicates was analyzed in two locations and in two years. We found a total of thirty five main-effect genomic regions controlling genistein, daidzein, glycitein and total isoflavones accumulation in seeds. The use of distinct environments permitted detection of a great number of environment-modulated and minor-effect QTL. Our findings suggest that isoflavone seed concentration is controlled by a complex network of multiple minor-effect loci interconnected by a dense epistatic map of interactions. We hypothesize that the magnitude and significance of the main and epistatic effects of the nodes in the network will vary depending on the genetic background and environmental conditions. In an attempt to unravel the genetic architecture underlying the traits studied, we searched on a genome-wide scale for genomic regions homologous to the most important identified isoflavone biosynthetic genes. We identified putative candidate genes for several of the main-effect and epistatic QTL and for QTL reported by other groups.