Wild wheat gene could boost nutrient content of modern varieties

"The reintroduction of the functional gene from the wild species into commercial wheat varieties has the potential to increase the nutritional value of a large proportion of our current cultivated wheat varieties,"​ said lead researcher Professor Jorge Dubcovsky from the University of California, Davis.

Over two billion people are reported to be deficient in zinc and iron, and more than 160 million children under the age of five lack an adequate protein supply, according to the World Health Organization.

The development and commercialization of this nutrient-rich wheat could therefore lead to a range of functional bakery with enhanced nutritional profiles.

The focus of the study is the gene GPC-B1, so-called for its effect on Grain Protein Content, found to be non-functional in all the cultivated pasta and bread wheat varieties analyzed by the researchers. This suggested that the functionality of the gene was lost during the domestication of wheat.

To test if the gene is responsible for accelerating grain maturity and increasing protein and micronutrient content, the researchers used a technique called RNA interference to create GM wheat lines with decreased levels of the GPC gene.

The researchers report in the new issue of Science​ that the transgenic experimental plants had significantly reduced levels of protein (30 per cent), zinc (36 per cent), and iron (38 per cent), compared to the non-transgenic controls.

"The results were spectacular,"​ said Dubcovsky. "The grains from the genetically modified plants matured several weeks later than the control plants and showed 30 percent less grain protein, zinc and iron, without differences in grain size. This experiment confirmed that this single gene was responsible for all these changes."​

Having shown that gene was behind the accelerated maturing and increased protein, zinc and iron content, Dubcovsky and his collaborators in the Wheat Coordinated Agricultural Project are now racing to introduce the GPC-B1 gene into U.S. wheat varieties using a rapid-breeding technique called Marker Assisted Selection.

The new varieties, bred by conventional rather than transgenic methods, used wild emmer wheat (Triticum turgidum​ ssp. dicoccoides​), ancestor of cultivated pasta wheat (T. turgidum​ ssp. durum​).

Several breeding programs are reported to have already used the GPC-B1 gene to develop elite breeding lines, which are close to being released as new wheat varieties.

Such varieties are now being tested by breeders in multiple environments to determine if the introduction of GPC-B1 has any negative impacts on factors such as yield and quality, and the researchers hope that these will soon translate into food products with enhanced nutritional value.

And concerns associated with transgenic crops are not valid with the new wheat variety, because: "The resulting varieties are not genetically modified organisms, which will likely speed their commercial adoption,"​ said a statement from the University of California, Davis.

"Wheat is one of the world's major crops, providing approximately one-fifth of all calories consumed by humans, therefore, even small increases in wheat's nutritional value may help decrease deficiencies in protein and key micronutrients,"​ said Dubcovsky.

Enhancement of the nutritional content of plants is gaining ever increasing scientific attention, with a number of traditionally cross-bred and genetically modified plants and crops coming to light considered to offer human health benefits, including zeaxanthin to potato tubers, and the omega-3 fatty acid, eicosapentaeoic acid (EPA), to soybeans and brassica, and stearidonic acid (SDA) in canola crops.

Source: Science​, 24 November 2006, Volume 314, pp. 1298-1301 "A NAC gene regulating senescence improves grain protein, zinc, and iron content in wheat"​ Authors: C. Uauy, A. Distelfeld, T. Fahima, A. Blechl, J. Dubcovsky