Modifying lysine biosynthesis and catabolism in corn with a single bifunctional expression/silencing transgene cassette

• Published in: Plant biotechnology journal Vol. 6; no. 1; p. 13
• Main Authors: Frizzi, Alessandra, Huang, Shihshieh, Gilbertson, Larry A, Armstrong, Toni A, Luethy, Michael H, Malvar, Thomas M
• Format: Journal Article
• Language: English
• Published: England 01-01-2008
• Subjects: Corynebacterium glutamicum - genetics; DNA, Complementary; Gene Expression; Gene Targeting; HSP70 Heat-Shock Proteins - genetics; Hydro-Lyases - genetics; Introns; Lysine - biosynthesis; Lysine - metabolism; Plants, Genetically Modified - metabolism; Repetitive Sequences, Nucleic Acid; RNA, Double-Stranded; Saccharopine Dehydrogenases - genetics; Seeds - enzymology; Seeds - metabolism; Transgenes; Zea mays - enzymology; Zea mays - genetics; Zea mays - metabolism
• ISSN: 1467-7652
• DOI: 10.1111/j.1467-7652.2007.00290.x

Although it is one of the major crops in the world, corn has poor nutritional quality for human and animal consumption due to its low lysine content. Here, we report a method of simultaneous expression of a deregulated lysine biosynthetic enzyme, CordapA, and reduction of a bifunctional lysine degradation enzyme, lysine-ketoglutarate reductase/saccharophine dehydrogenase (LKR/SDH), in transgenic corn plants by a single transgene cassette. This is accomplished by inserting an inverted-repeat sequence targeting the maize LKR/SDH gene into an intron of a transgene cassette that expresses CordapA. This combination of LKR/SDH silencing and CordapA expression led to the accumulation of free lysine to over 4000 p.p.m. in transgenic corn grain, compared to less than 100 p.p.m. in wild-type controls. This intron-embedded silencing cassette design reduces the number of transgene cassettes needed in transgenic approaches for manipulating metabolic pathways that sometimes require expression of one gene and silencing of another.