Identification of doubly transformed A. thaliana lines generated using the 'double dip' protocol. A: Growth of A. thaliana seedlings on MS3 plates containing both gentamicin (100 μg/mL) and kanamycin (50 μg/mL). Seeds were harvested from a mother plant that had simultaneously been transformed with respective A. tumefaciens ABI lines separately harboring pPZP211-FRB/NLuc (gentamicin-resistance) and pPZP221-FRB/NLuc (kanamycin-resistance). B: Growth of a replicate batch of double-dipped A. thaliana seedlings on gentamicin alone. C: Growth of a replicate batch of double-dipped A. thaliana seedlings on kanamycin alone. Circles in A-C indicate antibiotic resistant plants. D: An expanded view of a robust seedling growing on both gentamicin and kanamycin. E: Multiplex genomic PCR of FRB and FKBP sequences in genomic DNA from nine lines selected on gentamicin alone. F: Multiplex genomic PCR of FRB and FKBP sequences in nine lines selected on both antibiotics. "FKB" indicates the PCR product obtained from a known kanamycin-resistant transgenic line; "FRB" indicates the PCR product obtained from a known gentamicin-resistant transgenic line; "WT" represents the negative control using a non-transgenic line.