Integration of Transcriptomic and Metabolomic Strategies to Dissect Soybean Flavonoid Biosynthetic Network for Facilitating Metabolic Engineering of Soybean Nutrients

Soybean (Glycine max) is rich in different types of flavonoids, which play important roles in soybean symbiosis, biotic and abiotic stress responses, seed coat pigmentation, and seed oil synthesis. While isoflavnoids from soybean seeds greatly benefit adult female health as important nutraceuticals, their presence in soy-based infant formulas may be undesirable. Breeding of soybean cultivars with different isoflavonoids and other beneficiary flavonoids to fulfill the specific requirements of various age groups is highly expected. However, many details in flavonoid biosynthesis, transport and their regulations remain elusive and their metabolic engineering in soybean seeds has very limited success. We committed to revealing more secrets regarding biosynthesis, transport, and transcriptional regulation of flavonoids in soybean seeds from functional genome points of view, by taking advantages of published soybean genome sequence and partial transcriptomic and flavonoid metabolomic databases. Firstly, a more complete metabolomic database on soybean seed flavonoids will be constructed by using HPLC and LC-MS high throughput metabolite profiling technologies, with soybean cultivars of different flavonoid phenotypes. The same seed materials will also be used for flavonoid-related gene expression profiling by using Affymetrix Soybean Genechips and qRT-PCR method to establish transcriptomic databases. After analyzing and comparing metabolomic and transcriptomic databases, we could classify and associate groups of genes with end products of different types of flavonoids or even possibly decode the gene-metabolite correlation. These analyses should lead to discoveries of new and key genes involved in the biosynthesis, transport and transcriptional regulation of (iso)flavonoids. Characterization of these new key genes will pave the way for their application in metabolic engineering of soybean seed flavonoids and molecular breading of soybean cultivars with desirable flavonoid traits. Meanwhile，accumulation of genetic, molecular biology, and field trail resources and system setup on soybean research will enable us to explore broader agronomic traits regarding soybean yield, oil production, nitrogen fixation, nutrient acquisition, and stress tolerance for soybean genetic improvement.