New research has identified genes that control vitamin E content in maize grain, a finding that could lead to improving the nutritional profile of this staple crop.
Cornell 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 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.
“We have established a near-complete foundation for the genetic improvement of vitamin E in grain of maize and other major cereals,” said Michael Gore, associate professor of plant breeding and genetics and a co-corresponding author of the study published Oct. 2 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,” said Christine Diepenbrock, a graduate student in Gore’s lab, and the paper’s first author. “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.”
Out of the six novel genes, the researchers identified two that are homologs (similar in DNA sequence) but that are present in different regions of the genome. They discovered these genes encode a key chlorophyll biosynthetic enzyme. Chlorophyll is a green pigment responsible for the absorption of light to provide energy for photosynthesis. The finding was surprising because maize grain does not photosynthesize.
Studies done in the model plant Arabidopsis have shown that when leaves age and senesce (as when leaves turn color in the fall), chlorophyll degrades, and the tail end of the chlorophyll molecule’s chemical structure separates and is used in vitamin E synthesis. However, when researchers previously inactivated that degradation pathway, they found tocochromanol synthesis still occurred in Arabidopsis seed (which photosynthesizes) and younger leaves. The alternative process newly found in this study in maize, involving a chlorophyll biosynthetic enzyme, may also be taking place in these other tissues of Arabidopsis and in other major grain crops
The other co-corresponding author is Dean DellaPenna, professor of biochemistry and molecular biology at Michigan State University. Another coauthor is Edward Buckler, research geneticist at the U.S. Department of Agriculture-Agricultural Research Service and adjunct professor of plant breeding and genetics at the Institute for Genomic Diversity in Cornell’s Institute of Biotechnology.
The study was funded by the National Science Foundation, USDA-ARS, Cornell University startup funds, and USDA National Needs Fellowship.