Wednesday, May 12, 2004


Continuing with yesterday's theme, scientists have just noticed that huge chunks of so-called junk DNA are absolutely identical in human, rat, mouse, dog and chicken genomes, which means that they can't possibly be junk. Surprise! [Science abstract | BBC story]

Also, scientists at Simplot, the huge potato processor, have figured out how to modify the potato genome without using Agrobacterium. [Or so they say -- it seems to me that that they use it but manage to get rid of the offending DNA before producing the plants]. Regardless, this is very cool -- no markers means no Cauliflower Mosaic Virus, among other things. Rommens, et al., "Crop Improvement through Modification of the Plant's Own Genome," Plant Physiology 135 (May 2004), pp. 421-431. Abstract:

Plant genetic engineering has, until now, relied on the incorporation of foreign DNA into plant genomes. Public concern about the extent to which transgenic crops differ from their traditionally bred counterparts has resulted in molecular strategies and gene choices that limit, but not eliminate, the introduction of foreign DNA. Here, we demonstrate that a plant-derived (P-) DNA fragment can be used to replace the universally employed Agrobacterium transfer (T-) DNA. Marker-free P-DNAs are transferred to plant cell nuclei together with conventional T-DNAs carrying a selectable marker gene. By subsequently linking a positive selection for temporary marker gene expression to a negative selection against marker gene integration, 29% of derived regeneration events contain P-DNA insertions but lack any copies of the T-DNA. Further refinements are accomplished by employing -mutated virD2 and isopentenyl transferase cytokinin genes to impair T-DNA integration and select against backbone integration, respectively. The presented methods are used to produce hundreds of marker-free and backbone-free potato (Solanum tuberosum) plants displaying reduced expression of a tuber-specific polyphenol oxidase gene in potato. The modified plants represent the first example of genetically engineered plants that only contain native DNA.
USA Today discusses GM foods in the pipeline, including another GM wheat from Syngenta, allegedly due to come out in 2007.


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