The case of the super-starch spud

Why does a genetically modified potato designed for industrial paper production need resistance to antibiotics?


Andrew Leonard
March 6, 2007 11:07PM (UTC)

The classic potato consists of water, cell walls, and two kinds of starch: amylose and amylopectin. In Europe, the industrial starch industry makes use of both, but prefers amylopectin, which has thickening properties that make it useful for the paper, adhesives and textile industries. But there's a problem: Separating the amylose from the amylopectin is an energy- and water-intensive task with high economic costs.

The plant biotechnologists at Germany's BASF think they have an answer. They've genetically modified a potato variety so as to "turn off" the gene responsible for synthesizing amylose, creating a high-amylopectin potato known commercially as Amflora. Presto: a renewable source of industrial materials that no longer requires an energy-intensive separation process. Theoretically, then, Amflora could be considered environmentally friendly -- just what the plant doctor ordered for a carbon-constrained future.

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Regulatory approval for Amflora from the European Union had been expected by this spring, but GMO-Compass reports today that a new delay may push its commercial deployment back to 2008. Before making a final decision the European Commission wants an opinion from the European Medicines Agency, EMEA.

The issue is not whether high-amylopectin potatoes might be unhealthy for humans. The current regulatory question has to do with the "marker gene" introduced into the potato during the development process.

Genetically modifying an organism is something of a hit or miss process. In the lab, some cells are successfully modified but most are not, and it's very difficult to tell which cells have the trait you want and which don't. A commonly used technique is to link the new gene that has the desired trait with an accompanying marker gene that has a special property, such as being resistant to an antibiotic. After the modification process, all the cells are exposed to the antibiotic, and only the cells in which the new genes were successfully implanted survive. Those cells are then used to breed the new organism. The marker gene no longer serves any useful purpose, but it's there for keeps.

In the case of Amflora, the marker gene conveys resistance to the antibiotic kanamycin. According to GMO-Compass, there are some questions as to the importance of kanamycin for the veterinary industry. The worry appears to be that if Amflora's modified genes get into the food chain, kanamycin's effectiveness may be diminished.

How realistic is that possibility? BASF claims that the chances are nil, and so far, Amflora's gotten a clean bill of health from regulatory authorities, although Friends of the Earth spokesperson Claire Oxborrow has been reported as saying that female rats who were fed the transgenic potato exhibited variations in spleen weight from rats that were fed its unmodified parent cultivar. In any event, Europe is extremely persnickety about these matters, so the approval process could continue indefinitely.

Persnicketiness when regulating genetically modified organisms strikes me as a good thing. But what I find most interesting about the case of the super-starch spud is not just the attempt to balance the environmentally friendly aspects of a high starch potato with the potential downside of increasing kanamycin resistance, but the fact that the current sticking point has to do with a gene whose only purpose is to tell scientists whether they've succeeded in modifying the DNA of an organism, and not because that gene has any properties desirable in the long run. Seems like there should be a better way.

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Andrew Leonard

Andrew Leonard is a staff writer at Salon. On Twitter, @koxinga21.

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