Nitrilase enzymes specific for the hydrolysis of the nitrile group of benzonitriles, eg. bromoxynil or ioxynil, nucleotide sequences encoding for such enzymes, and transformed cells in which the nitrilase expression is foreign are provided. The transformed cells are capable of expressing the nitrilase enzyme to provide detoxification of an environment and protect benzonitrile herbicide-sensitive cells from its cytotoxic effect. Plants are developed which are resistant to bromoxynil.
