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ARS Home » Southeast Area » Raleigh, North Carolina » Soybean and Nitrogen Fixation Research » Research » Publications at this Location » Publication #174655
Title: METABOLIC PROFILING OF AMINO ACIDS IN SOYBEAN DEVELOPING SEEDS: POSSIBLE ROLE OF ASPARAGINE IN THE CONTROL OF STORAGE PRODUCT ACCUMULATION

Author
item SEBASTIA, C - UIUC
item MARSOLAIS, F - AGRI-FOOD CANADA
item SARAVITZ, C - NCSU
item Israel, Daniel
item DEWEY, R - NCSU
item Huber, Steven

Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2004
Publication Date: 1/15/2005
Citation: Sebastia, C.H., Marsolais, F., Saravitz, C., Israel, D.W., Dewey, R.E., Huber, S.C. 2005. Metabolic profiling of amino acids in soybean developing seeds: possible role of asparagine in the control of storage product accumulation. Journal of Experimental Botany.56:1951-1964.

Interpretive Summary: Increasing seed protein content, while maintaining oil content and yield, is an important objective for soybean breeding programs. A fundamental understanding of the biological mechanisms that control the accumulation of protein and oil during seed development may contribute to this goal. A major question is whether seed protein content is controlled by the maternal plant (e.g. supply of nitrogenous assimilates) or by the developing seed itself (e.g. intrinsic capacity to synthesize storage proteins versus oil). To address this, we evaluated N-assimilate supply in vivo to developing seeds of two closely related genotypes, differing in protein content at maturity, by analyzing the profile and concentration of amino acids in the maternal tissues (seed coat and apoplast) and the filial soybean cotyledons at mid-maturation stage. Our analyses show that high seed protein content at maturity is specifically associated with higher contents of Asn within the developing cotyledons. IMPACT: Our results suggest that the Asn content of developing cotyledons may be a determinant of storage protein biosynthesis. If so, the Asn content of developing seeds could be useful as a physiological marker for high seed protein content and perhaps as a target for manipulation in order to influence seed protein content.

Technical 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 embryos 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 ß-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 to NC103, whereas at the seed coat and apoplast level 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 (MS-ACCase). In the third study, a positive correlation between free Asn in developing cotyledons and seed protein content (SPC) at maturity was confirmed in a comparison of five unrelated field-grown cultivars. Our findings support the hypothesis that high SPC in soybean is determined by the capacity of the embryo to uptake 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.