A transient duplication of the acetolactate synthase gene in a cell culture of Datura innoxia.
A 2.0 kb fragment of the yeast ILV2 gene, which codes for the target enzyme acetolactate synthase (ALS) of the herbicide chlorsulfuron, was shown to hybridize to the nuclear DNA of a haploid cell culture of Datura innoxia P. Mill. Nuclear DNA of a chlorsulfuron resistant line of D. innoxia, CSR6, gave a prominent 2.65 kb band when cleaved by either EcoRI or HindIII. The 2.65 kb band has been shown to hybridize with the yeast ILV2 probe. A herbicide resistant line descended from CSR6 by continuous culture resulted in the loss of the 2.65 kb restriction fragment. These observations suggest that CSR6 resulted from a large tandem duplication of the ALS gene and that a point mutation for herbicide resistance in an ALS gene repeat unit of the duplication was selected during subsequent growth of the resistant line.
Department of Biology, University of Saskatchewan, S7N 0W0, Saskatoon, Saskatchewan, Canada.
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