Figure 1.—

Assay for recombination between divergent repeats. A schematic of the assay construct is shown, before (top) and after (bottom) recombination. The GU-npt-US construct (top) contains two overlapping halves of the β-glucuronidase GUS gene, GU and US, with the U (618 bp) overlapping region and the NPTII neomycin phosphotransferase gene (npt) as spacer in between the direct repeats. Mutations are introduced in the U part of the GU half. Homologous recombination between the U divergent repeats gives rise to an active GUS reporter gene (bottom). Such event is recognized as a blue sector upon X-gluc histological staining in the daughters of the cell where HR occurred. RB and LB represent the right and left borders of the pMLBART binary vector, respectively. The npt arrow indicates the gene transcription direction. The BAR gene confers resistance to phosphinothricin (BASTA) and was used for transformation selection.