Developments in plant breeding for improved nutritional quality of soya beans I. Protein and amino acid content

By E. Clarke, J. Wiseman. Journal of Agricultural Sciences, 2000

84 citations recorded by the source corpus.

Soya beans, like other legumes, contain low concentrations of the nutritionally essential sulphur amino acid, methionine. Cysteine, although not an essential amino acid because it can be synthesized from methionine, also influences the nutritional quality of soya bean products when it is only present in low levels. A low cysteine content will also aggravate a methionine deficiency. Soya bean lines deficient in 7S protein subunits have been identified. The 7S proteins contain substantially less methionine and cysteine than the 11S proteins. With the myriad of genetic null alleles for these subunits it may be possible to tailor the 7S/11S storage protein ratio and their total composition in seeds to include only those subunits with the richest sulphur amino acid composition. Cotyledon feeding experiments, using isolated soya bean cotyledons, demonstrated that addition of methionine to the culture media caused increased synthesis of both proteins and free amino acids but the mechanism by which this takes place is not clear. Biotechnological approaches to improve nutritional value of soya beans include elevated expression of genes that originate from other species which encode high-sulphur proteins. High level expression of a 2S Brazil nut albumin gene in soya bean resulted in raised methionine concentration although the Brazil nut gene is highly antigenic and therefore will not be useful in production agriculture. Modification of glycinin to increase sulphur amino acid content is possible, and these gene products are capable of normal assembly into trimers in vitro although are rapidly degraded in vivo by the asparaginyl endopeptidase responsible for post-translational modification of proglycinin. Solutions to the methionine deficiency may be anticipated from a combination of approaches followed in laboratories worldwide. Many of these approaches are not without difficulty but, despite this, the likelihood is that soya beans with improved nutritional quality (which may not be confined to sulphur-containing amino acids as other nutritionally essential amino acids are also valuable) will be available in the near future. It will be essential to confirm that the increased total methionine (or other amino acid) is digestible to the animal to at least the same degree as conventional cultivars.

Subfields: Plant Science

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Citations in the corpus

Genomic Regions Associated with Amino Acid Composition in Soybean (2005, background): “This is particularly important when synthetic amino acids are used to obtain the desired ratios (Clarke and Wiseman 2000).”
Achievements and Challenges in Improving the Nutritional Quality of Food Legumes (2015, background): “As an alternative to breeding for improved quality (Clarke and Wiseman, 2000; Caccialupi et al., 2010; Gawlik-Dziki and Świeca, 2011), food processing improves or converts the physical and biochemical properties of relatively bulky, perishable and typically inedible raw materials into more useful, v”
The effect of dietary protein replacement by crystalline amino acid on growth and nitrogen utilization of turbot Scophthalmus maximus juveniles (2005, background): “Therefore, dietary EAA unbalances may occur when these commodities are used in diet formulation (Clarke and Wiseman, 2000).”
Genetic Mapping and Confirmation of Quantitative Trait Loci for Seed Protein and Oil Contents and Seed Weight in Soybean (2013, background): “Seed protein and seed size play significant roles in determining quality of soy food products (Clarke and Wiseman, 2000; Friedman and Brandon, 2001).”