Milk-Bundle Proteins Improve Seed Nutritional Quality of Transgenic Soybean

There has been great progress achieved with genetic engineering in improving soybean protein quality. However, these improvements are not sufficient to meet the nutritional requirements for food and feed. This recent study aimed to increase soybean sulfur amino acid content by expressing the de novo Milk Bundle protein MB-16, in transgenic soybean seed.

The MB-16 gene, originally developed for expression in rumen bacteria, was introduced into the soybean (Glycine max (L.) Merrill) genome to improve its seed nutritional quality. MB-16 codes for a de novo protein enriched in the essential amino acids (EAA) methionine, threonine, lysine and leucine. Constructs were designed using the soybean codon bias, with and without the KDEL ER retention sequence.

Transformed events showed the same transcription pattern as those with the soybean codon preference, but the transcript levels were lower at each developmental stage. MB-16 protein levels were highest in full-sized green seed, but virtually disappeared in mature seeds. However, amino acid analysis of mature transgenic seeds showed a significant increase in methionine and cysteine as compared to the parent. This indicates that MB-16 elevated the sulfur amino acids, improved the EAA seed profile and confirms that a de novo synthetic gene can enhance the nutritional quality of soybean.

Read more about this promising study at http://link.springer.com/article/10.1007/s11248-013-9777-5/fulltext.html.