Genetic Boost Sends Insects Packing – and Maybe Controversy Too

Instead of introducing an alien gene – as is done, for example, to create Bt corn – Dr. Barry Shelp, a plant biochemist at the University of Guelph, amplifies the activity of a gene already present in the plant.

“I actually used the gene that was in the tobacco plant and just pumped it up. So it's a gene that is already there,” says Dr. Shelp.

It’s an approach he believes might ultimately lead to greater public acceptance of genetic manipulation technology. “I've always been concerned about the backlash against transgenic species, and I was trying to do whatever I could to make certain that didn't happen in my program.”

The gene in question produces GABA, a potent neurotoxin. GABA is naturally produced by all plants in response to stress, such as insects chewing on their leaves and even the pressure of an insect footfall on a leaf.

Dr. Shelp added a chunk of DNA known as a “promoter” to greenhouse tobacco plants. The promoter switched the GABA gene permanently into the “on” position, turning the plants into 24/7 GABA producers. The impact on pests was dramatic. During a three-month experiment, egg-laying by root-knot nematode – a common pest worldwide – was reduced by up to 90 per cent.

Researchers at Brock University, including Dr. Shelp's long-time colleague Dr. Alan Bown (now retired) and Masters student Kennaway MacGregor, attained similar reductions with tobacco budworm larvae.

The work is summarized in the November issue of the Canadian Journal of Botany.

Dr. Shelp says the boosted GABA levels had no impact on the tobacco plants' appearance. However, he says, while his lab's research demonstrated proof-of-concept, evidence from another lab shows that having a full-time GABA promoter can sap too much energy from a plant, thereby stunting it.

“If you're careful to choose the right level of GABA expression then that doesn't present a problem,” says Dr. Shelp, who is continuing 15 years of GABA research by looking at how to fine-tune GABA output, and developing GABA-boosted tomato plants.

He says earlier work with GABA in humans (in which it is also a natural part of the nervous system) shows that eating large amounts of GABA has no neurological effect, making enhanced GABA levels apparently safe in food crops. However, he notes that GABA-enhanced tea leaves are sold as a treatment for hypertension in several Asian countries.

Dr. Shelp is currently waiting for a ruling on his patent application for GABA-enhanced crops. While he believes the technique is safe and could potentially be used in a wide variety of crops, he says that the largest hurdle to commercialization is still the fact that the technique involves genetic alteration.

“Five years from now genetically manipulated plants will be in much broader use,” insists Dr. Shelp. “Given the enormous benefits they offer, including reducing the amount of chemical pesticides used, it's just a matter of time before they become just another plant.”

Dr. Barry Shelp
Tel.: (519) 824-4120, ext. 53089
E-mail: bshelp@uoguelph.ca

Dr. Shelp's article “Gamma aminobutyrate: from intellectual curiosity to practical pest control” in the November issue of the Canadian Journal of Botany is available for free download at: http://pubs.nrc-cnrc.gc.ca/cgi-bin/rp/rp2_vols_e?cjb.