trans soybean











Soybean plants in the greenhouse


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Soybean (Glycine max [L.] Merr) is considered an excellent source of protein and oil for humans and livestock. However, soybean seed proteins are deficient in the sulfur-containing amino acids cysteine and methionine. An estimate of $100 million is spent annually by the poultry and swine industry to supplement feeds with synthetic methionine in order to achieve optimal growth and development of animals consuming grain-soybean meal rations. Since soybean is the principal seed meal used in feeds, developing soybean cultivars with high sulfur amino acid content could influence the economy and production of the livestock and poultry industry. Although high protein soybean lines are available, varieties expressing the adequate levels of cysteine have not been developed through traditional breeding. Transgenic methods as an effort to increase the overall cysteine content in soybean have been employed. In this study genetic manipulation of two key enzymes involved in cysteine biosynthesis is reported, serine acetyltransferase (SAT) and O-acetylserine(thiol)lyase (OAS-TL). Both genes were overexpressed in soybean through molecular techniques. The levels of both enzymes were higher in transgenic soybean than that of untransformed plants, suggesting that production of cysteine and related sulfur-containing compounds can be enhanced by metabolic engineering and genetic manipulation of the enzymes involved is sulfur assimilatory pathway.