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Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only Publication Acceptance Date: 11/2/2003 Publication Date: 3/1/2005 Citation: Krishnan, H.B. 2005. Engineering soybean for enhanced sulfur amino acid content [abstract]. ASA-CSSA-SSSA Annual Meeting Abstracts. 45:454-461. Interpretive Summary: Technical Abstract: Although soybean is an important source of dietary protein, the sulfur amino acid content is not sufficient to meet the methionine requirements of human infants and monogastric animals. Increasing the concentration of sulfur amino acids would enhance the quality of soybean proteins consumed by both humans and animals. Conventional breeding and genetic engineering have been employed by several groups to elevate the sulfur amino acid content of soybeans. Brazil nut 2S albumin has been introduced into soybeans, which resulted in a 40 to 50% increase in methionine content. Since the 2S albumin proved to be an allergen, commercial cultivars were not developed and released. Another methionine-rich protein, a 15 kD zein, when expressed in soybean resulted in 12-20% increase in methionine content. We have successfully introduced a novel 11 kD delta zein in soybean. The introduced protein accumulated within endoplasmic reticulum-derived protein bodies, which were found in transitional cells occurring between vascular tissue and storage parenchyma cells. Although accumulation of the 11 kD delta zein increased methionine content of the alcohol-soluble protein 1.5 to 1.7 fold, overall methionine content of the seed flour was not altered. These results suggest that even though it is possible to obtain a modest increase in soybean sulfur amino acid content, several challenges remain to be resolved to obtain an increase sufficient for human and animal dietary needs. |
