On the inverse correlation of protein and oil: Examining the effects of altered central carbon metabolism on seed composition using soybean fast neutron mutants

Authors: KAMBHAMPATI, SHRIKAAR - Danforth Plant Science Center; AZNAR-MORENO, JOSE - Kansas State University; HOSTETLER, COOPER - Danforth Plant Science Center; CASO, TARA - Danforth Plant Science Center; Bailey, Sally; HUBBARD, ALLEN - Danforth Plant Science Center; DURRETT, TIMOTHY - Kansas State University; Allen, Douglas - Doug

Submitted to: Metabolites
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2019
Publication Date: 12/28/2019
Citation: Kambhampati, S., Aznar-Moreno, J.A., Hostetler, C., Caso, T., Bailey, S.R., Hubbard, A.H., Durrett, T.P., Allen, D.K. 2019. On the inverse correlation of protein and oil: Examining the effects of altered central carbon metabolism on seed composition using soybean fast neutron mutants. Metabolites. 10(1):18. https://doi.org/10.3390/metabo10010018.
DOI: https://doi.org/10.3390/metabo10010018

Interpretive Summary: Soybeans are one of the most important crops globally, valued for high levels of protein and oil that contribute soybean meal for animal diets and vegetable oil for human nutrition. In this study we investigate the carbon trade-offs through soybean metabolism that contribute throughout the life cycle of seed growth and development and result in final levels of protein and lipid. Specifically, late during the maturation of seeds, lipid levels decline, and carbohydrates in the form of polymers called oligosaccharides are elevated. Since there is no new carbon from the plant late in development to the maturing seed, we hypothesized that some of the carbon from lipids may be reallocated to the carbohydrates. Here we report an analysis of the trade-offs in the levels of carbohydrates, protein and oil to better understand the relationships in these important end products. Our data suggest how seed metabolism may be augmented in the future to make a better soybean and benefit agriculture.

Technical Abstract: Protein and oil levels measured at maturity are inversely correlated across soybean lines; however, carbon is in limited supply during maturation resulting in tradeoffs for the production of other reserves including oligosaccharides. During the late stages of seed development, the allocation of carbon for storage reserves changes. Lipid and protein levels decline while concentrations of indigestible raffinose family oligosaccharides (RFOs) increase, leading to a decreased crop value. Since the maternal source of carbon is diminished during seed maturation stages of development, carbon supplied to RFO synthesis likely comes from an internal, turned-over source and may contribute to the reduction in protein and lipid content in mature seeds. In this study, fast neutron (FN) mutagenized soybean populations with deletions in central carbon metabolic genes were examined for trends in oil, protein, sugar, and RFO accumulation leading to an altered final composition. Two lines with concurrent increases in oil and protein, by combined 10%, were identified. A delayed switch in carbon allocation towards RFO biosynthesis resulted in extended lipid accumulation and without compromising protein. Strategies for future soybean improvement using FN resources are described.