title: Crop improvement through modification of the plant's own genome.
abstract: Plant genetic engineering has, until now, relied on the incorporation of foreign DNA into plant genomes. Public concern about the extent to which transgenic crops differ from their traditionally bred counterparts has resulted in molecular strategies and gene choices that limit, but not eliminate, the introduction of foreign DNA. Here, we demonstrate that a plant-derived (P-) DNA fragment can be used to replace the universally employed Agrobacterium transfer (T-) DNA. Marker-free P-DNAs are transferred to plant cell nuclei together with conventional T-DNAs carrying a selectable marker gene. By subsequently linking a positive selection for temporary marker gene expression to a negative selection against marker gene integration, 29% of derived regeneration events contain P-DNA insertions but lack any copies of the T-DNA. Further refinements are accomplished by employing Omega-mutated virD2 and isopentenyl transferase cytokinin genes to impair T-DNA integration and select against backbone integration, respectively. The presented methods are used to produce hundreds of marker-free and backbone-free potato (Solanum tuberosum) plants displaying reduced expression of a tuber-specific polyphenol oxidase gene in potato. The modified plants represent the first example of genetically engineered plants that only contain native DNA.
authors.affiliation: J.R. Simplot Company, Simplot Plant Sciences, Boise, Idaho 83706, USA. crommens@simplot.com
authors.forename: Caius M
authors.initials: CM
authors.lastname: Rommens
authors.forename: Jaime M
authors.initials: JM
authors.lastname: Humara
authors.forename: Jingsong
authors.initials: J
authors.lastname: Ye
authors.forename: Hua
authors.initials: H
authors.lastname: Yan
authors.forename: Craig
authors.initials: C
authors.lastname: Richael
authors.forename: Lynda
authors.initials: L
authors.lastname: Zhang
authors.forename: Rachel
authors.initials: R
authors.lastname: Perry
authors.forename: Kathleen
authors.initials: K
authors.lastname: Swords
mesh_terms: D001483:Base Sequence; D018556:Crops, Agricultural / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics; D005818:Genetic Engineering / Q000379:methods; D005819:Genetic Markers / Q000235:genetics; D018745:Genome, Plant; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D011198:Solanum tuberosum / Q000235:genetics; D014026:Nicotiana / Q000235:genetics
chemical_list: D018744:DNA, Plant; D005819:Genetic Markers