title: Modifying lysine biosynthesis and catabolism in corn with a single bifunctional expression/silencing transgene cassette.
abstract: 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.
authors.affiliation: Mystic Research, Monsanto Company, 62 Maritime Drive, Mystic, CT 06355, USA.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Frizzi
authors.forename: Shihshieh
authors.initials: S
authors.lastname: Huang
authors.forename: Larry A
authors.initials: LA
authors.lastname: Gilbertson
authors.forename: Toni A
authors.initials: TA
authors.lastname: Armstrong
authors.forename: Michael H
authors.initials: MH
authors.lastname: Luethy
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Malvar
mesh_terms: D048230:Corynebacterium glutamicum / Q000235:genetics*; D018076:DNA, Complementary; D015870:Gene Expression; D018390:Gene Targeting; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D006836:Hydro-Lyases / Q000235:genetics*; D007438:Introns; D008239:Lysine / Q000096:biosynthesis* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism; D012330:RNA, Double-Stranded; D012091:Repetitive Sequences, Nucleic Acid; D012443:Saccharopine Dehydrogenases / Q000235:genetics*; D012639:Seeds / Q000201:enzymology / Q000378:metabolism; D019076:Transgenes; D003313:Zea mays / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; D018840:HSP70 Heat-Shock Proteins; D012330:RNA, Double-Stranded; D012443:Saccharopine Dehydrogenases; D006836:Hydro-Lyases; C020040:4-hydroxy-tetrahydrodipicolinate synthase; D008239:Lysine