The BXN™ cotton line was genetically engineered to express tolerance to oxynil herbicides, including bromoxynil and ioxynil. Oxynil herbicides act by blocking electron flow during the light reaction of photosynthesis, inhibiting cellular respiration in dicotyledonous plants. Oxynil herbicides applied at rates recommended for effective weed control are toxic to conventional cotton varieties. The modified cotton line BXN™ contains the bxn gene for oxynil tolerance, and allows farmers to use oxynil herbicides for weed control in the cultivation of cotton.

The bxn gene was isolated from the bacterium Klebsiella pneumoniae subspecies ozaenae and codes for the enzyme nitrilase, which hydrolyses ioxynil and bromoxynil into non-toxic compounds. The nitrilase encoding gene was introduced into the cotton genome using Agrobacterium-mediated transformation, and the bacterial form of the enzyme expressed in this transgenic cotton line functions the same as that found in monocot plants such as corn, wheat and barley.

The kanamycin-resistance gene (aphII), isolated from the bacterium Escherichia coli codes for an enzyme (aminoglycoside 3'-phosphotransferase II) that phosphorylates kanamycin , thereby preventing it from binding to ribosomes and rendering the cells resistant. This protein is ubiquitous in the environment and it degrades rapidly in vitro in simulated mammalian gastric and intestinal fluids.