03 Nov 2017 --- New research from Cornell University, US, has identified genes that control vitamin E content in maize grain, a finding that could lead to an improvement in the nutritional profile of the staple crop.

Cornell University scientists and colleagues from other institutions combined different types of genetic association analyses to identify 14 genes across the genome that were involved in the synthesis of vitamin E.

Six genes were newly discovered to encode proteins that contribute to a class of antioxidant compounds called tocochromanols, collectively known as vitamin E. Along with antioxidant properties, tocochromanols have been associated with good heart health in humans and proper functioning in plants.

Identifying best lines of crop
“Improvement of nutritional quality in crops can in some cases be achieved by finding the existing lines that have the highest nutritional quality and crossing them together,” Christine Diepenbrock, a Ph.D. candidate at Cornell University and the paper’s first author, tells NutritionInsight. “We can often find those ‘best’ lines more quickly and inexpensively by examining the genetic sequence of hundreds or thousands of varieties, whereas conducting nutritional analyses on populations of that size would be prohibitive.”

“This study effectively tells us where to look when we examine that genetic sequence, i.e. which very narrow regions of the maize genome are involved in producing vitamin E,” Diepenbrock explains.

“We have established a near-complete foundation for the genetic improvement of vitamin E in grain of maize and other major cereals,” says Michael Gore, Associate Professor of Plant Breeding and genetics and a co-corresponding author of the study published in the journal The Plant Cell.

“There has been talk, among breeders working to increase provitamin A in maize, that we could increase vitamin E at the same time,” says Diepenbrock. “They are related compounds biochemically, and tocochromanols are essential for seed viability in that they prevent seed oils from going rancid throughout seed storage, germination and early seedling development.”

Important to global nutrition
Vitamin E is an essential nutrient that is often at suboptimal levels in human beings, in some cases reaching clinical deficiency, which has symptoms of impaired balance and coordination and muscle weakness, Diepenbrock notes, adding: “Vitamin E compounds are also antioxidants, which are generally beneficial to health throughout human and animal systems.”

“In addition to being associated with cardiovascular health and immune function in humans, these compounds help to keep seeds in a state that they can germinate and also increase the shelf life of oils and lipid-rich foods; these functions are important in ensuring a food supply that is sufficient both in quality and quantity,” Diepenbrock says.

Diepenbrock tells NutritionInsight of future studies: “We are working on follow-up experiments with the two genes encoding an enzyme involved in chlorophyll biosynthesis, namely to determine how these genes, which have both conserved their function, work together in the plant across space (e.g. within the different compartments of the grain) and time.”

It will also be important to test whether these two genes are associated with vitamin E levels in other major grain crops like wheat and sorghum, Diepenbrock adds.

“These crops, like maize, also have grain that does not photosynthesize but still makes the forms of vitamin E found to be associated with these genes in maize grain,” says Diepenbrock. “The process found in maize that links vitamin E levels to a chlorophyll biosynthetic enzyme may be active in these other crops, or there may be some other alternative process that has not yet been found.”

By Paul Creasy