Selectable marker used in Flavr Savr tomato transformation was:
Selectable marker deployed for Flavr Savr regeneration was neomycin phosphotransferase II gene nptII from Tn5 transposon of Escherichia coli, conferring resistance to aminoglycoside antibiotics kanamycin, neomycin, G418 and paromomycin. Enzyme mechanism involves transfer of gamma phosphate from ATP to 3' hydroxyl of aminoglycoside, inactivating drug ability to bind 16S rRNA of 30S ribosomal subunit, preventing misreading and bactericidal action. Tomato cotyledon explants co-cultivated with Agrobacterium harboring antisense PG plus nptII under nos promoter placed on Murashige and Skoog organogenesis medium supplemented with kanamycin 100 mg/L, carbenicillin to kill Agrobacterium, and phytohormones zeatin and IAA for shoot induction. Only transformed cells expressing NPTII detoxify antibiotic and proliferate, untransformed bleached die. Selection efficiency typically 5-15% transformation. nptII favored because plants lack endogenous resistance, assayable by ELISA and NPTII dot blot, and safety profile extensive showing rapid proteolysis in simulated gastric fluid with half-life
Ref: Beck et al. Gene 1982 Tn5 nptII; Coruzzi et al. EMBO J 1984 Plant selectable markers; NIH.