T-DNA structures (not to scale) from a) pN6-Bxb1; b) pCOXS3-Bxb1; and c) predicted single copy T-DNA structures after excision of stuffer by Bxb1- att recombination. PCR primers shown as e, f, g, h; att sites as grey arrowheads; hybridization probes as grey rectangles. Abbreviations: B, BamHI; E, EcoRI; V, EcoRV, RB, T-DNA right border; LB, T-DNA left border, POXS3 Arabidopsis OXS3 promoter. Length in kb of PCR products (dotted lines) and DNA fragments (dashed lines). d) Sequence of the 51 bp attP and 42 bp attB Bxb1 recognition sites, where the minimal required sequence is underlined and the 2 nucleotide 'gt' core region of crossover is in bold. e) sequence of a PCR product detecting a conservative site-specific excision event. Not shown are gene terminators and promoters for hptII (hygromycin phosphotransferase II) and nptII (neomycin phosphotransferase II) and gusA (β-glucuronidase).