Free amino acid profiles suggest a possible role for asparagine in the control of storage-product accumulation in developing seeds of low- and high-protein soybean lines

Abstract

Several approaches were taken to examine the role of N-assimilate supply in the control of soybean (Glycine max) seed composition. In the first study, developing seeds were grown in vitro with D-[U-14C]sucrose (Suc) and different concentrations of Gln. Light stimulated carbon flux into oil and protein, and was required to sustain Suc uptake and anabolic processes under conditions of elevated nitrogen supply. High Gln supply resulted in higher transcript levels of beta-conglycinin and oleosin. In the second study, analyses of soluble amino acid pools in two genetically related lines, NC103 and NC106 (low- and high-seed protein, respectively) showed that, in the light, NC106 accumulated higher levels of Asn and several other amino acids in developing cotyledons compared with NC103, whereas at the seed coat and apoplast levels both lines were similar. In the dark, NC103 accumulated Gln, Arg, and its precursors, suggesting a reduced availability of organic acids required for amino acid interconversions, while NC106 maintained higher levels of the pyruvate-derived amino acids Val, Leu, and Ile. Comparing NC103 and NC106, differences in seed composition were reflected in steady-state transcript levels of storage proteins and the lipogenic enzyme multi-subunit acetyl CoA carboxylase. In the third study, a positive correlation (P < or = 0.05) between free Asn in developing cotyledons and seed protein content at maturity was confirmed in a comparison of five unrelated field-grown cultivars. The findings support the hypothesis that high seed-protein content in soybean is determined by the capacity of the embryo to take up nitrogen sources and to synthesize storage proteins. Asn levels are probably tightly regulated in the embryo of high-protein lines, and may act as a metabolic signal of seed nitrogen status.

Seed-Specific Expression of a Feedback-Insensitive Form of CYSTATHIONINE-γ-SYNTHASE in Arabidopsis Stimulates Metabolic and Transcriptomic Responses Associated with Desiccation Stress

“…5A). Higher protein levels may affect the levels of lipids and starch, as reported previously (Hernández-Sebastià et al, 2005;Matityahu et al, 2013). Measurement of the total lipids in SSE seeds revealed a slight decrease only in the SSE 2 line, although not statistically significant (Fig.…”

Dynamics of physiological and biochemical changes during somatic embryogenesis of Acca sellowiana

“…Sucrose and amino acids, mainly asparagine and glutamine, were the primary carbon and nitrogen sources available for soybean embryo germination (Rainbird et al 1984). A positive correlation was observed between free asparagine and the storage protein content in soybean seeds (Hernández-Sebastià et al 2005). In the present work, ornithine was not detected at any evaluated developmental stage, suggesting that whole synthesized ornithine was converted into arginine.…”

Carbon and Nitrogen Provisions Alter the Metabolic Flux in Developing Soybean Embryos

“…Embryos receive sugars and amino acids and convert them into storage reserves through primary metabolism. Thus, the accumulation of protein and oil is controlled by both the maternal (Fabre and Planchon, 2000;Nakasathien et al, 2000;Pipolo et al, 2004) and seed (Wilcox, 1998;Narvel et al, 2000;Hernández-Sebastià et al, 2005) genotypes, which complicates efforts to gain fundamental understanding of the process.…”