OTTAWA
www.burberryit.net, May 5 (UPI) -- Canadian scientists have developed a new technique of bioengineered contraception that could someday prevent the uncontrolled spread of genetically engineered crops while still allowing farmers to reseed their crops year after year.
The novel approach could thereby avoid the controversy surrounding the "terminator" scheme, involving genes that would make bioengineered plants infertile. The terminator method compels farmers to buy seeds every year instead of simply cultivating them from past harvests.
"All growers are environmental stewards whose livelihood depends on the protection of their resources," molecular geneticist Johann Schernthaner of Agriculture and Agri-Food Canada in Ottawa, Canada
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Some 145 million acres of genetically modified -- GM -- crops are now planted in the world. Environmentalists and scientists remain concerned over these crops since they could breed with related species or their wild cousins resulting in the unwanted spread of engineered traits. Plants engineered to produce beneficial drugs, for example, could potentially cross-pollinate with natural crops leading inadvertently to drug-laced cereal and other problems.
Schernthaner and colleagues wanted to create a method to block genetic contamination from plants known to readily breed with relatives, such as maize. The method they came up with is fundamentally linked to sex.
"Every higher organism has two sets of nearly identical genetic information, one from each parent," Schernthaner said. Essentially, the researchers designed the plants so these pairs of genes worked as locks and keys for one another, leading to sterile plants if separated in progeny.
The scientists first inserted a gene for seed lethality, or SL, into tobacco plants. These plants grew normally, but their seeds failed to sprout because they overproduced the plant growth hormone auxin.
"Auxin is not toxic. It's a natural component," Schernthaner said.
They also engineered tobacco plants containing a repressor -- R -- gene that suppressed the auxin-related gene. In findings made public Monday from the Proceedings of the National Academy of Sciences, when both these bioengineered plants were bred together, crops with viable seeds resulted. These plants could in theory be raised generation after generation through self-pollination.
However, when tobacco possessing both SL and R genes were bred with normal tobacco plants -- as might happen accidentally in the field -- the SL and R genes became separated among the progeny. Seeds possessing the SL gene only failed to sprout.
Obviously, Schernthaner said this remained experimental because seeds possessing the R gene survived.
"It is not a perfect system yet and improvements to it would be the next stage," Schernthaner noted.
He explained one logical next step would be to engineer plants with two sets of SL and R genes. Males would contribute one collection of SL and R genes, while females would have their own pair of SL and R genes. The male R gene would only suppress the female SL gene, and vice versa.
Plant molecular biologist Henry Daniell of the University of Central Florida in Orlando cautioned the repressor gene used in these experiments was "leaky," since it did not work every time.
"To be applied in the field, the repressor will have to be made watertight," Schernthaner admitted.
Daniell added a number of other problems exist. For instance, with current biotechnology
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(Reported by Charles Choi, UPI Science News, in New York.)related articles：
