title: Gene conversion in transgenic maize plants expressing FLP/FRT and Cre/loxP site-specific recombination systems.
abstract: DNA recombination reactions (site-specific and homologous) were monitored in the progeny of transgenic maize plants by bringing together two recombination substrates (docking sites and shuttle vectors) in the zygotes. In one combination of transgenic events, the recombination marker gene (yellow fluorescent protein gene, YFP) was activated in 1%-2% of the zygotes receiving both substrates. In other crosses, chimeric embryos and plants were identified, indicative of late recombination events taking place after the first mitotic division of the zygotes. The docking site structure remained unchanged; therefore, all recovered recombination events were classified as gene conversions. The recombinant YFP-r gene segregated as a single locus in subsequent generations. The recombination products showed evidence of homologous recombination at the 5' end of the YFP marker gene and recombinational rearrangements at the other end, consistent with the conclusion that DNA replication was involved in generation of the recombination products. Here, we demonstrate that maize zygotes are efficient at generating homologous recombination products and that the homologous recombination pathways may successfully compete with other possible DNA repair/recombination mechanisms such as site-specific recombination. These results indicate that maize zygotes provide a permissive environment for homologous recombination, offering a new strategy for gene targeting in maize.
authors.affiliation: Pioneer Hi-Bred International, A DuPont Business, Research Center, 7300 NW 62nd Avenue, Johnston, IA 50131-1004, USA.
authors.forename: Vesna
authors.initials: V
authors.lastname: Djukanovic
authors.forename: Waclaw
authors.initials: W
authors.lastname: Orczyk
authors.forename: Huirong
authors.initials: H
authors.lastname: Gao
authors.forename: Xifan
authors.initials: X
authors.lastname: Sun
authors.forename: Nicole
authors.initials: N
authors.lastname: Garrett
authors.forename: Shifu
authors.initials: S
authors.lastname: Zhen
authors.forename: William
authors.initials: W
authors.lastname: Gordon-Kamm
authors.forename: Joanne
authors.initials: J
authors.lastname: Barton
authors.forename: L Alexander
authors.initials: LA
authors.lastname: Lyznik
mesh_terms: D001287:Attachment Sites, Microbiological; D003433:Crosses, Genetic; D004254:DNA Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism*; D005785:Gene Conversion; D018390:Gene Targeting; D005819:Genetic Markers; D005822:Genetic Vectors; D019426:Integrases / Q000235:genetics / Q000378:metabolism*; D008164:Luminescent Proteins / Q000032:analysis; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000196:embryology / Q000378:metabolism*; D011995:Recombination, Genetic; D012639:Seeds / Q000235:genetics / Q000254:growth & development; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D003313:Zea mays / Q000196:embryology / Q000235:genetics*
chemical_list: D005819:Genetic Markers; D008164:Luminescent Proteins; D010940:Plant Proteins; D014157:Transcription Factors; C045073:Cre recombinase; D004254:DNA Nucleotidyltransferases; C045119:FLP recombinase; D019426:Integrases