Influence of carbon to nitrogen ratios on soybean somatic embryo (cv. Jack) growth and composition

Abstract

Soybean [Glycine max (L.) Merr.] seed are valued for their protein and oil content. Soybean somatic embryos cultured in Soybean Histodifferentiation and Maturation (SHaM) medium were examined for their suitability as a model system for developing an understanding of assimilate partitioning and metabolic control points for protein and oil biosynthesis in soybean seed. This report describes the growth dynamics and compositional changes of SHaM embryos in response to change in the carbon to nitrogen ratio of the medium. It was postulated that at media compositions that were sufficient to support maximal growth rates, changes in the C:N ratio are likely to influence the partitioning of resources between the various storage products, especially protein and oil. As postulated, at steady-state growth rates, embryo protein content was strongly correlated with decreasing C:N ratios and increasing glutamine consumption rates. However, oil content remained relatively unchanged across the C:N ratio range tested, and resources were instead directed towards the starch and residual biomass (estimated by mass balance) pools in response to increasing C:N ratios. Protein and oil were inversely related only at concentrations of sucrose in the medium <88mM, where carbon limited growth and no starch was found to accumulate in the tissues. These observations and the high reproducibility in the data indicate that SHaM embryos are an ideal model system for the application of metabolic flux analysis studies designed to test hypotheses regarding assimilate partitioning in developing soybean seeds.

Amino Acid Balance is Affected by Protein Concentration in Soybean

“…The concept of C and N limitations to oil and protein yield formation is based on reported findings in embryo culture (Truong et al, 2013) and helps contextualize the results of these source-sink treatments. The concept of C and N limitations to oil and protein yield formation is based on reported findings in embryo culture (Truong et al, 2013) and helps contextualize the results of these source-sink treatments.…”

“…In other words, a reduced C/N ratio available to the developing seed under shade likely resulted in an increased seed protein concentration indirectly through reduced oil concentration. The concept of C and N limitations to oil and protein yield formation is based on reported findings in embryo culture (Truong et al, 2013) and helps contextualize the results of these source-sink treatments. Additionally, research on highprotein genotypes has shown that these lines yield less than normal protein lines (Serretti et al, 1994; due to reduced seed set, which afforded greater N reserves per seed.…”

Tracking the metabolic pulse of plant lipid production with isotopic labeling and flux analyses: Past, present and future

“…In developing seeds or cell-culture suspensions metabolism operates at a pseudo steady state during periods of development, therefore isotopically labeling these tissues with a mixture of labeled and unlabeled substrates will result in redistribution of the isotope that reflects pathway use and flux. Such studies have been regularly performed with metabolic flux analysis to document the partitioning of carbon, energy and reducing equivalents to oil, protein and carbohydrate in seeds or cell cultures [57][58][59][60][61][62][63][64]. However steady state labeling analyses are limited to assessments of pathways that enzymatically rearrange the distribution of isotope.…”

“…At the biochemical level these studies have provided insight to wild-type metabolic operation as well as the response to genetic or environmental conditions. By changing the temperature [226], oxygen [62,227] nutrient status [57,61,63,64,228] or through genetic manipulation of central metabolism [59,229,230], or lipid metabolism [120] plant cells are forced to rebalance resource utilization resulting in altered phenotypes.…”

Variation in Seed‐Quality Traits of Chickpea and Their Correlation to Raffinose Family Oligosaccharides Concentrations

“…***Significant at the P ≤0.001. Starch and protein biosynthesis depend on the carbon to nitrogen ratio (C:N) and have shown positive and negative correlations with C:N, respectively (Truong et al, 2013). ‡ ns, not significant.…”