Expression of the mutant Arabidopsis thaliana acetolactate synthase gene confers chlorsulfuron resistance to transgenic poplar plants.

The mutant acetolactate synthase ( crs1-1) gene from Arabidopsis thaliana, which confers resistance to the herbicide chlorsulfuron, was transferred to a hybrid poplar ( Populus tremula×P. alba) using two Agrobacterium-mediated transformation methods (co-inoculation and co-cultivation). Two different constructs were used. In one, the mutant crs1-1 gene was placed under the control of its own promoter, and, in the other, this gene was under the control of the duplicated cauliflower mosaic virus 35S promoter (70 promoter). The transformation efficiency ranged from 22 to 32% of the tumours in co-inoculation and from 67 to 77% of the stem explants in co-cultivation experiments. The usefulness of the herbicide chlorsulfuron as a selectable marker gene was also demonstrated. Successful genetic transformation was verified by Southern and northern analyses and enzyme activity. Plants carrying the crs1-1 mutant gene under the control of the 70 promoter showed high levels of transcription and activity whereas plants carrying the native crs1-1 gene showed low levels of expression. However, transgenic plants expressing each of the chimaeric crs1-1 genes are completely resistant to high doses of chlorsulfuron in greenhouse tests. [ABSTRACT FROM AUTHOR]