title: Ds excision from extrachromosomal geminivirus vector DNA is coupled to vector DNA replication in maize.
abstract: Analysis of transposition products generated after Activator (Ac) excision from the P locus in maize suggest that Ac excises either during or after replication of the P locus. The frequency of excision of the non-autonomous Ac derivative, Dissociation (Ds), from extrachromosomal replicating and nonreplicating vector DNAs in transfected black mexican sweet maize protoplasts was compared to assess directly a role of extrachromosomal vector DNA replication in Ds excision. Replicating (rep+) and nonreplicating (rep-) vector DNAs comprised a Ds element that harbored a geminivirus, wheat dwarf virus (WDV), origin of replication and WDV genes required for viral DNA replication (rep+) or mutant, inactive derivatives of these genes (rep-). Excision of Ds was detected only in those cell nuclei co-transfected with the replicating Ds-vector DNA and a transposase expression vector. Quantitative reconstruction experiments showed that Ds excised at least 3 x 10(5)-fold more frequently from replicating vector DNA as compared with nonreplicating vector DNA. Therefore, these results provide direct evidence for a coupling of Ds excision from extrachromosomal vector DNA to vector DNA replication in maize.
authors.affiliation: Department of Plant Pathology, University of California, Berkeley 94720, USA.
authors.forename: U
authors.initials: U
authors.lastname: Wirtz
authors.forename: B
authors.initials: B
authors.lastname: Osborne
authors.forename: B
authors.initials: B
authors.lastname: Baker
mesh_terms: D002467:Cell Nucleus; D004261:DNA Replication; D004251:DNA Transposable Elements / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics; D004279:DNA, Viral; D017791:Geminiviridae / Q000235:genetics; D005822:Genetic Vectors; D010947:Plants, Toxic; D010957:Plasmids; D011523:Protoplasts; D011995:Recombination, Genetic; D012093:Replicon; D014026:Nicotiana / Q000235:genetics; D014162:Transfection; D003313:Zea mays / Q000235:genetics* / Q000821:virology
chemical_list: D004251:DNA Transposable Elements; D018744:DNA, Plant; D004279:DNA, Viral