Plant selection principle based on xylose isomerase |
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Authors: | Anna Haldrup Michael Noerremark Finn Thyge Okkels |
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Institution: | (1) Danisco Biotechnology, Langebrogade 1, P.O. Box 17, 1001 Copenhagen K, Denmark;(2) Present address: Plant Biochemistry Laboratory, Department of Plant Biology, The Royal Veterinary and Agricultural University, 40 Thorvaldsenvej, DK-1871 Frederiksberg C Copenhagen, Denmark;(3) Present address: Medi-Cult a/s, Moellehaven 12, DK-4040 Jyllinge, Denmark |
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Abstract: | Summary The xylose isomerase genes (xylA) from Thermoanaerobacterium thermosulfurogenes and Streptomyces rubiginosus were introduced and expressed in three plant species (potato, tobacco and tomato) and transgenic plants were selected on
xylose-containing medium. The xylose isomerase genes were transferred to explants of the target plant by Agrobacterium-mediated transformation. The xylose isomerase genes were expressed under the control of the enhanced cauliflower mosaic virus
35S promoter and the Ω′ translation enhancer sequence from tobacco mosaic virus. In potato and tomato, xylose isomerase selection
was more efficient than the established kanamycin selection. The level of enzyme activity in the regenerated transgenic plants
selected on xylose was 5–25-fold higher than the enzyme activity in control plants selected on kanamycin. The xylose isomerase
system enables transgenic cells to utilize xylose as a carbohydrate source. In contrast to antibiotic or herbicide resistance-based
system where transgenic cells survive on a selective medium but nontransgenic cells are killed, the xylose system is an example
of a positive selection system where transgenic cells proliferate while non-transgenic cells are starved but still survive.
The results show that a new selection method, is established. The xylose system is devoid of the disadvantages of antibiotic
or herbicide selection, and depends on an enzyme which is already being widely utilized in specific food processes and that
is generally recognized as safe for use in the starch industry. |
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Keywords: | glucose isomerase plant transformation selectable markers positive selection rhannose |
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