Herbicide-resistant plants carrying mutated acetolactate synthase genes
1990
Hartnett, M.E. | Chui, C.F. | Mauvais, C.J. | McDevitt, R.E. | Knowlton, S. | Smith, J.K. | Falco, S.C. | Mazur, B.J.
Acetolactate synthase (ALS) is the target enzyme for three unrelated classes of herbicides, the sulfonylureas, the imidazolinones, and the triazolopyrimidines. We have cloned the genes which specify acetolactate synthase from a variety of wild type plants, as well as from plants which are resistant to these herbicides. The molecular basis of herbicide resistance in these plants has been deduced by comparing the nucleotide sequences of the cloned sensitive and resistant ALS genes. By further comparing these sequences to ALS sequences obtained from herbicide-resistant yeast mutants, two patterns have become clear. First, the ALS sequences that can be mutated to cause resistance are in domains that are conserved between plants, yeast and bacteria. Second, identical molecular substitutions in ALS can confer herbicide resistance in both yeast and plants. These findings have been extended by oligonucleotide directed in vitro mutagenesis of plant ALS genes, followed by introduction of the mutated genes into sensitive plants. The herbicide-resistant transgenic plants so produced provide additional evidence for the commonality of mutations which specify herbicide resistance in ALS genes. Some implications of this work for predicting and addressing the problem of herbicide-resistant weeds are discussed.
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