Scientists from Rutgers University in the US have inserted a bacterial gene into corn to enable the crop to produce methionine, one of the nine essential amino acids that humans get from food.
Methionine is needed for growth and tissue repair, improves the tone and flexibility of skin and hair, and strengthens nails. The sulfur in methionine protects cells from pollutants, slows cell aging and is essential for absorbing selenium and zinc.
“We improved the nutritional value of corn, the largest commodity crop grown on Earth,” said Thomas Leustek, study co-author and professor in the Department of Plant Biology in the School of Environmental and Biological Sciences. “Most corn is used for animal feed, but it lacks methionine - a key amino acid - and we found an effective way to add it.”
Implications for animal feed
The development could also help reduce worldwide animal feed costs: Every year, synthetic methionine worth several billion dollars is added to field corn seed, which lacks the substance in nature.
“It is a costly, energy-consuming process,” explained Joachim Messing, a professor at the Waksman Institute of Microbiology Messing and the study senior author. “Methionine is added because animals won't grow without it. In many developing countries where corn is a staple, methionine is also important for people, especially children. It's vital nutrition, like a vitamin.”
Chicken feed is usually prepared as a corn-soybean mixture, and methionine is the sole essential sulfur-containing amino acid that's missing, explained the paper in the Proceedings of the National Academy of Sciences (PNAS).
In the developed world, including the U.S., meat proteins generally have lots of methionine, said Dr Leustek. But in the developing world, subsistence farmers grow corn for their family's consumption.
“Our study shows that they wouldn't have to purchase methionine supplements or expensive foods that have higher methionine,” he said.
The Rutgers scientists inserted a gene from E. coli into the corn plant's genome, which coded for the enzyme 3’-phosphoadenosine-5’-phosphosulfate reductase (EcPAPR). The resulting genetically modified corn accumulated 57% more methionine than a high-methionine non-GM variety. It was also able to promote weight gain in chicks versus non-GM seeds in chicken feeding trial.
“To our surprise, one important outcome was that corn plant growth was not affected,” said Dr Messing.
2017, Volume 114, Number 43, Pages 11386-11391
“Engineering sulfur storage in maize seed proteins without apparent yield loss”
Authors: J Planta, et al.