On the Inverse Correlation of Protein and Oil: Examining the Effects of Altered Central Carbon Metabolism on Seed Composition Using Soybean Fast Neutron Mutants

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. of 153-12% of biomass is present as sugars and oligosaccharides [4]. Sugars, such as sucrose, represent a metabolizable energy source in animal feed, but raffinose and stachyose that are members of the raffinose family oligosaccharides (RFOs) are indigestible and undesirable for livestock production [5,6]. RFOs have hypothesized roles in seed desiccation tolerance [7-9], stability of liposomes during dehydration, and seed germination [10][11][12], although efforts in breeding and genetic engineering have demonstrated that reduced levels do not impact seed viability [13][14][15]. The RFO and sucrose levels are the result of central carbon metabolism and could adversely impact the levels of oil and protein, which are known to be inversely correlated in mature seeds [16][17][18][19][20][21].Protein and lipid accumulation over the course of seed development is dependent on the supply of amino acids and sugars from the maternal sources (i.e., organic carbon assimilated in the leaf) as well as the metabolism within the developing seed (i.e., cotyledons) [22][23][24][25]. The levels of intermediates of central carbon (C) and nitrogen (N) metabolism that are precursors for storage reserve production, vary depending on the stage of reproductive development and may indicate temporal changes in metabolism [26][27][28]. During maturation, 10-15% of lipids are degraded [28][29][30], coinciding with RFO accumulation, and occurring at the time when there are little to no exogenous resources supplied by the maternal plant. The expression of genes involved in gluconeogenesis and glyoxylate cycle suggest carbon remobilization from lipid may occur. Along with existing sucrose present late in development, carbon from lipid could contribute to central metabolism and enable RFO pro...

Analyzing Mass Spectrometry Imaging Data of 13C-Labeled Phospholipids in Camelina sativa and Thlaspi arvense (Pennycress) Embryos

“…Unlabeled and 64 h labeled Camelina tissue separated into embryo axis and cotyledon, were extracted using a phase separation method, previously described with slight modifications [ 50 ]. Briefly, 700 µL of 3:1 ( v / v ), chloroform: methanol solution was added to dried lyophilized tissue along with 10 µL of EquiSPLASH ® (Avanti polar lipids, Birmingham, AL, USA) as labeled internal standard mix.…”

Workflow for the Quantification of Soluble and Insoluble Carbohydrates in Soybean Seed

“…Pearson correlation analysis was also performed for each location ( Figure 5 ). Despite the well-known negative correlation between oil and protein [ 13 ] that was observed in both locations (r ≤ −0.51, p < 0.05), new correlations were identified. In agreement with PC3 loading coefficients ( Figure S4, Table S2 ), although maltose content is low in comparison to the other sugars ( Table S3 ), it showed a significant positive correlation with oil in both locations (r ≥ 0.42, p < 0.05) and a negative correlation with protein that was significant in AR (r ≤ −0.48, p < 0.05), with the same tendency in NC (r ≤ −0.4, p < 0.1, Figure 5 ).…”

“…It has been hypothesized that carbon derived from the turnover of lipids and proteins contributes to the synthesis of RFOs. A recent study using fast neutron-mutagenized soybean populations with deletions in central carbon metabolic genes showed that a delayed switch in carbon allocation towards RFO biosynthesis resulted in extended lipid accumulation without compromising protein content [ 13 ].…”

A TMT-based quantitative proteomic analysis provides insights into the protein changes in the seeds of high- and low- protein content soybean cultivars

“…The ammonia derived from nitrogen uptake by maternal vegetative tissues is the primary source for supply the nitrogen predominantly as amino acid such as glutamine and asparagine to the seeds (Ohyama et al 2017). In addition, amino acids participate in the synthesis of storage proteins and thereby contributing the carbon remobilization through proteolysis activity during the late seed developmental stages (Galili et al 2014;Kambhampati et al 2020). Here, 64 proteases showed increased abundance in Saedanbaek that might be having a crucial role in the remobilization of endogenous nitrogenous products such as amino acid or proteins to storage proteins (Gallardo et al 2006(Gallardo et al , 2007.…”

“…Moreover, during seed maturation stages, 10 to 15% of lipids are converted to raffinose family oligosaccharides (RFOs) when the supply of exogenous resources from maternal plants are limited (Kambhampati et al 2020). These RFOs aere produced by carbon remobilization from lipid along with sucrose during the development of seeds (Kambhampati et al 2020).…”