RESEARCH-PGR: A Genome-level Approach to Balancing the Vitamin Content of Maize Grain

This collaborative research project is directed at identifying a subset of the ~40,000 genes in the corn genome that work together to determine the levels of five essential and limiting dietary vitamins in kernels: vitamin E and the four B vitamins, B1 (thiamin), B2 (riboflavin), B3 (niacin) and B6 (pyridoxine). By combining approaches similar to those used in the Human Genome project, the researchers will identify alleles, special variations in these “vitamin” genes, and learn how to put them together to generate high amounts of vitamins in corn kernels. An important outcome of this research will be the knowledge by which to enhance these micronutrient levels in corn kernels such that diets in which maize is a major component provide a balanced nutritional content. Such direct translation of these findings will be the eventual incorporation and fixation of identified alleles in maize breeding programs that are favorable for the increased levels of vitamins E and B to enhance the food and feed supply chain. In addition, this research will provide guiding principles for parallel efforts in other agricultural crops and thus enable predictive breeding and metabolic engineering of more nutritious crops worldwide. Finally, integration of research with education within the project will permit training of the next generation of plant scientists with knowledge of plant genetics, breeding, genomics, biochemistry, and bioinformatics.

This project seeks to leverage the tremendous genetic and genomic tool sets developed in maize the past decade to advance and accelerate our fundamental understanding of the genes, alleles and genetic mechanisms controlling synthesis and accumulation of vitamins that are limiting in maize grain and hence result in vitamin deficiencies in maize-based diets: four B vitamins (B1, thiamine; B2, riboflavin; B3, niacin; B6, pyridoxine) and vitamin E. This project brings together a team of scientists with divergent but complementary knowledge and skills that together will allow the genes, alleles and underlying mechanisms controlling these nutritional traits to be elucidated and the knowledge deployed on a global scale. Specific objectives are to (i) perform genome-wide association studies with the maize Ames inbred line panel (n~2,000) to identify and resolve quantitative trait loci (QTL) controlling accumulation of these micronutrients; (ii) assess the role of rare alleles by constructing and analyzing segregating F2 populations derived from Ames lines that are extreme outliers for traits; (iii) determine the contribution of expression QTL and presence-absence variants (PAVs) to vitamin composition using whole transcriptome sequencing data obtained from grain 24 days after pollination in 500 inbred lines that represents the phenotypic variation of the Ames panel; and, (iv) perform genomic prediction with the Ames panel to accelerate the efficiency of breeding improved grain micronutrient composition in developing countries. The broader impacts of this project to the broader scientific community and public will be ensured through a set of coordinated activities that engage students, postdoctoral associates, scientists and the public. Data and biological resources generated in this project will be made accessible to the community. Data will be disseminated through publications, project websites and long-term repositories such as the NCBI’s SRA and MaizeGDB.