Genetic engineering for high methionine grain legumes

Müntz, Klaus; Christov, V.; Saalbach, Gerhard; Saalbach, Isolde; Waddell, David R.; Pickardt, Thomas; Schieder, O.; Wüstenhagen, T.

doi:10.1002/(sici)1521-3803(199808)42:03/04<125::aid-food125>3.3.co;2-1

Cited by 53 publications

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“…The Brazil nut albumin acts as a strong methionine sink which, in soya bean, out-competes the formation of at least some of the other methionine-containing endogenous proteins. In addition, Muntz et al (1997) reported that the increased methionine levels occurred at the cost of other non-protein sulphur compounds. It is not yet known whether the total amount of sulphur-containing compounds that can be formed in transgenic seeds is limited by available sulphur.…”

Section: Increasing Content Of High Methionine Protein In Soya Beansmentioning

confidence: 99%

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

Clarke

Wiseman

2000

J. Agric. Sci.

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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.

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Section: Increasing Content Of High Methionine Protein In Soya Beansmentioning

confidence: 99%

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

Clarke

Wiseman

2000

J. Agric. Sci.

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“…Major field crops, which either directly or indirectly (as animal feed) make up the majority of the diets of most human populations, are deficient in one or more of the aspartate-derived amino acids. These deficiencies include lysine and threonine in cereals (Debadov, 2003;Pfefferle et al, 2003), methionine and threonine in legumes (Muntz et al, 1998), as well as methionine and isoleucine in potatoes (Stiller et al, 2007). Amino acids that are produced synthetically or by fermentation are often added to animal feed to improve its nutritive value.…”

Section: Introductionmentioning

confidence: 97%

Aspartate-Derived Amino Acid Biosynthesis inArabidopsis thaliana

Jander

Joshi

2009

The Arabidopsis Book

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The aspartate-derived amino acid pathway in plants leads to the biosynthesis of lysine, methionine, threonine, and isoleucine. These four amino acids are essential in the diets of humans and other animals, but are present in growthlimiting quantities in some of the world's major food crops. Genetic and biochemical approaches have been used for the functional analysis of almost all Arabidopsis thaliana enzymes involved in aspartate-derived amino acid biosynthesis. The branch-point enzymes aspartate kinase, dihydrodipicolinate synthase, homoserine dehydrogenase, cystathionine gamma synthase, threonine synthase, and threonine deaminase contain well-studied sites for allosteric regulation by pathway products and other plant metabolites. In contrast, relatively little is known about the transcriptional regulation of amino acid biosynthesis and the mechanisms that are used to balance aspartatederived amino acid biosynthesis with other plant metabolic needs. The aspartate-derived amino acid pathway provides excellent examples of basic research conducted with A. thaliana that has been used to improve the nutritional quality of crop plants, in particular to increase the accumulation of lysine in maize and methionine in potatoes.

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“…Asp-derived amino acids Lys, Met, Thr, and Ile are essential to humans and other animals, but they are present in major food crops at suboptimal levels (Müntz et al, 1998;Debabov, 2003;Pfefferle et al, 2003;Stiller et al, 2007). Genetic engineering of crop species with improved contents of Asp-derived amino acids requires a deep and comprehensive understanding of the metabolic pathways of these essential amino acids .…”

Section: Discussionmentioning

confidence: 99%

“…In major field crops, such as corn (Zea mays), rice (Oryza sativa), soybean (Glycine max), and potato (Solanum tuberosum), Asp-derived amino acids Lys, Met, Thr, and Ile are present at levels that limit the nutritional values (Müntz et al, 1998;Debabov, 2003;Pfefferle et al, 2003;Stiller et al, 2007). Increasing the contents of these amino acids in crop plants has long been a major goal of traditional breeding and genetic engineering Ufaz and Galili, 2008;Jander and Joshi, 2009).…”

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confidence: 99%

Analysis of Loss-of-Function Mutants in Aspartate Kinase and Homoserine Dehydrogenase Genes Points to Complexity in the Regulation of Aspartate-Derived Amino Acid Contents

Clark

2015

Plant Physiol.

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ORCID IDs: 0000-0002-8396-8388 (T.J.C.); 0000-0002-3374-7376 (Y.L.).Biosynthesis of aspartate (Asp)-derived amino acids lysine (Lys), methionine (Met), threonine (Thr), and isoleucine involves monofunctional Asp kinases (AKs) and dual-functional Asp kinase-homoserine dehydrogenases (AK-HSDHs). Four-week-old loss-of-function Arabidopsis (Arabidopsis thaliana) mutants in the AK-HSDH2 gene had increased amounts of Asp and Aspderived amino acids, especially Thr, in leaves. To explore mechanisms behind this phenotype, we obtained single mutants for other AK and AK-HSDH genes, generated double mutants from ak-hsdh2 and ak mutants, and performed free and protein-bound amino acid profiling, transcript abundance, and activity assays. The increases of Asp, Lys, and Met in ak-hsdh2 were also observed in ak1-1, ak2-1, ak3-1, and ak-hsdh1-1. However, the Thr increase in ak-hsdh2 was observed in ak-hsdh1-1 but not in ak1-1, ak2-1, or ak3-1. Activity assays showed that AK2 and AK-HSDH1 are the major contributors to overall AK and HSDH activities, respectively. Pairwise correlation analysis revealed positive correlations between the amount of AK transcripts and Lys-sensitive AK activity and between the amount of AK-HSDH transcripts and both Thr-sensitive AK activity and total HSDH activity. In addition, the ratio of total AK activity to total HSDH activity negatively correlates with the ratio of Lys to the total amount of Met, Thr, and isoleucine. These data led to the hypothesis that the balance between Lys-sensitive AKs and Thrsensitive AK-HSDHs is important for maintaining the amounts and ratios of Asp-derived amino acids.

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Genetic engineering for high methionine grain legumes

Cited by 53 publications

References 0 publications

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

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

Aspartate-Derived Amino Acid Biosynthesis inArabidopsis thaliana

Analysis of Loss-of-Function Mutants in Aspartate Kinase and Homoserine Dehydrogenase Genes Points to Complexity in the Regulation of Aspartate-Derived Amino Acid Contents

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