Maize is known in many English-speaking countries as corn but is technically a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable or starch. The Olmec and Mayans cultivated it in numerous varieties throughout central and southern Mexico. Between 1700 and 1250 BC, the crop spread through much of the Americas. The region developed a trade network based on surplus and varieties of maize crops. After European contact with the Americas in the late 15th and early 16th centuries, explorers and traders carried maize back to Europe and introduced it to other countries. Now the discovery of a new provisioning gene in maize plants that regulates the transfer of nutrients from the plant to the seed could lead to increased crop yields and improve food security. Scientists from Oxford University and the University of Warwick, in collaboration with agricultural biotech research company Biogemma-Limagrain, have identified the gene, called Meg 1.
Genetically modified maize is hardly new. They have been often deliberately genetically modified to have agronomically desirable traits. Traits that have been engineered into corn include resistance to herbicides and resistance to insect pests, the latter being achieved by incorporation of a gene that codes for the Bacillus thuringiensis toxin. Hybrids with both herbicide and pest resistance have also been produced. In 2009, transgenic maize was grown commercially in 11 countries, including the United States (where 85% of the maize crop was genetically modified), Brazil (36% GM), Argentina (83% GM), South Africa (57% GM), Canada (84% GM), the Philippines (19% GM) and Spain (20% GM).
The new finding, which the researchers believe could help to increase global food production, in this week’s Current Biology.
Unlike the majority of genes, which are expressed from both maternal and paternal chromosomes, Meg1 is expressed only from the maternal chromosomes. This unusual form of uniparental gene expression, termed imprinting, also occurs with some genes in humans, which regulate the development of the placenta to control the supply of maternal nutrients during foetal growth.
The team, led by Dr Jose Gutierrez-Marcos of the University of Warwick, and Dr Liliana Costa and Professor Hugh Dickinson of Oxford University’s Department of Plant Sciences, has now highlighted that plants have also adopted a similar system to regulate nutrient provisioning during seed development.
The researchers demonstrated that Meg1 is responsible for the formation of specialized conduit cells that confer placenta-like properties to the embryo surrounding tissues of plant seeds to regulate the transfer of nutrients from mother to offspring.
Dr Gutierrez-Marcos of the University of Warwick said: "These findings have significant implications for global agriculture and food security, as scientists now have the molecular know-how to manipulate this gene by traditional plant breeding or through other methods in order to improve seed traits, such as increased seed biomass yield.
"This understanding of how maize seeds and other cereal grains develop (e.g. in rice and wheat) is vital, as the global population relies on these staple products for sustenance. Therefore to meet the demands of the world’s growing population in years to come, scientists and breeders must work together to safeguard and increase agricultural production."
For further information: http://www.ox.ac.uk/media/news_stories/2012/120113.html
Photo: Luis Miguel Bugallo Sánchez