Regulation of Seed Protein Concentration in Soybean by Supra‐Optimal Nitrogen Supply

Abstract

nificant barriers to development of high-protein commercial cultivars. The physiological and biochemical basis for increased seed proteinSoybean SPC is inherited as a quantitative trait (Burconcentrations (SPC) observed in restriction-index, recurrent-selec- ton, 1987) and influenced by environmental effects tion breeding programs with soybean [Glycine max (L.) Merr.] are poorly understood. The hypothesis that soybean SPC is regulated by (Burton, 1988). Generally the trait is much less influthe supply of nitrogenous substrates available to the seed was evaluenced by the genotype of the embryo than by the genoated. Effects of supra-optimal external N on seed storage protein type on which the seeds develop (Singh and Hadley, accumulation, amino acid concentration and composition in leaves 1968). This suggests that whole plant processes such as and seeds at R5, and levels of specific storage protein subunits were N acquisition, translocation, and mobilization of C and measured. Genotypes with different SPC (NC 107, normal; N87-984-N are important in the determination of seed protein 16, intermediate; and NC 111, high) were grown in controlled-environconcentration. ment chambers and supplied with 30 mM N as NH 4 NO 3 from V5 to Brim and Burton (1979) used recurrent selection to maturity or from R5 to maturity. Control plants received 10 mM N increase SPCs in two populations (IA and IIA). Carter throughout the growth cycle. Relative to control, supra-optimal N et al. (1982) examined relationships between N accumuincreased SPC of NC 107 and N87-984-16 by an average of 28%. Greater enhancement of protein accumulation than of dry matter lation and distribution and SPC in high and low seed accumulation in the seed resulted in SPCs of 460 to 470 g kg Ϫ1 , germplasm from both populations. They observed that which are appreciably greater than concentrations observed for these high protein germplasm from population IA accumucultivars grown in the field. Supra-optimal N also increased SPC of lated more total N before reproductive development the high protein line (NC 111) by 15%, but this increase resulted than high seed protein germplasm in population IIA. entirely from a decrease in yield. Supra-optimal N supplied to NC Selected high and low seed protein lines derived from 107 and N87-984-16 from V5 until R5 increased total free amino acid Cycle 0 and advanced cycles of selection for both popuconcentrations in seeds and leaves at R5 by an average of 21 and lations were evaluated for vegetative N accumulation 46%, respectively. Enhanced accumulation of the ␤ subunit of ␤ prior to reproductive growth and vegetative N mobilizaconglycinin which does not contain methionine and cysteine accounted tion to seed during reproductive growth (Burton et al., for the increase in SPC. While enhanced N availability increased the SPC of a normal protein line into the high range, availability of sulfur 1995). The authors concluded that the high protein conamino acids in the developing seed determined which storage protein centration trait re...

Positional effects on soybean seed composition during storage

“…Variability in protein and oil content existed among the nodes (Escalante and Wilcox 1993a;Bennett et al 2003;Guleria et al 2007) and these differences have been attributed to environmental factors (Wolf et al 1982;Maestri et al 1998). Nakasathein et al (2000) demonstrated that the relative mobility of each nutrient at different node position generated high nitrogen to sulphur ratio in the apical position of the stem axis, which was conducive to accumulate enhanced dry matter rich in the protein subunits (Bennett et al 2003). Correspondingly nitrogen and sulfur would be less in basal part of the plant making available the precursors for the synthesis of lipids.…”

Influence of genotype on protein and oil concentration of soybean seeds

“…Taking into consideration the gain obtained in protein rates as a result of the cultivation in vitro with 20 and 40 mM glutamine concentrations, it was evident that the increase in protein rate occurred when the glutamine was increased. Nakasathien et al (2000) suggested that a cultivar with a regular concentration of protein in the seed had a biochemical capability of synthesizing more protein when N was available. When the cultivars were compared, there was an important statistical difference (P<0.05) for all the glutamine concentrations in both the cultivations in vitro and in vivo, while the CD 206 cultivar presented the highest averages of protein rates.…”

Herbicides Effect on Nitrogen Cycling in Agroecossystems

“…GDH is an enzyme of N metabolism that usually reaches a higher degree of activity during senescence (Ragster & Chrispeels, 1981;Laurière & Daussand, 1983). NH 4 + is available for transformation in the composts of N transport, such as glutamine and asparagine (Ghosh et al, 1995;Nakasathien et al, 2000), and some of the ions are converted into NH 3 according to the following balanced reaction:…”