Removal of Antibiotic Resistance Gene From Transplastomic Plants
The production of transplastomic plants has generally been achieved through efficient selection of cells/tissues with transformed chloroplasts using aadA gene, which encodes for aminoglycoside 3 adenyl transferase and confers resistance to the antibiotics spectinomycin and streptomycin. About 10,000 copies of aadA gene are present per cell of transplastomic plants, so that the high copy number and strong expression jncreases the potential risk of aadA-transfer from transplastomic plants to bacteria.

Recombination between the direct repeats present in the inserted expression cassette successfully resulted in excision and removal of either (i) the marker genes aadA and uidA gene leaving. bar gene, or that of (ii) aadA and bar genes, leaving uidA gene in the transplastomic tobacco plants. More such approaches for getting marker gene-free transplastomic plants will be developed and used in future.