Trait Selection, the Human Microbiome and Health
By Nate Korth, FFAR Fellow
The plant breeders and geneticists I know all make the same joke, “We breed for three traits: yield, yield and yield”. The seeming hyperbole of this statement fades when you consider the traits improved in crops over the last thousand years. While we focus on disease or drought resistance, the trait we’re really talking about is yield. The work conducted to improve crop yield is truly amazing and must be continued; however, in the pursuit of yield, many traits related to food nutrition have been overlooked.
Enter the support of the Foundation for Food & Agriculture Research(FFAR) for the Nebraska Food for Health Center (NFHC), a collection of scientists from diverse backgrounds: plant science, food science, microbiology, medical science and more, united with a shared goal: reimagining breeding practices to improve human health. We are not the first– golden rice and other biofortified grains have been improved to benefit human nutrition. My research at the NFHC contributes this new direction in plant breeding, combining known associations between diet, human gut microbes, health and disease with trait selection to improve the nutritional content of the food.
The human gut microbiome has gained attention in modern science as new technologies allow us to learn about gut microbes without having to culture them. We are discovering new associations between the gut microbiome and diseases such as Crohn’s disease or type II diabetes. This emerging knowledge helps form the basis of my research. The number-one driver of microbiome composition and function is long-term diet. Improving crops through selective breeding in the context of microbiome utilization, especially grains that comprise a majority of many human diets, can improve human health.
Quality Protein Maize (QPM) is one example of a staple crop that has been improved with human nutrition in mind, based on a natural mutation that changes amino acid profiles in the seed. Most plant proteins, especially grains, have an incomplete protein. This means the plant lacks at least one amino acid that humans are unable to make. If the grain is the primary source of protein in a person’s diet, it can lead to a deficiency in that amino acid and the development of the disease. Maize naturally has low levels of two essential amino acids: lysine and tryptophan, because most of the plant’s amino acids are housed in large and relatively simple storage proteins. To address this problem researchers developed QPM, which contains all eight essential amino acids.
The opaque2 mutation in maize deactivates a storage protein and ultimately results in a complete protein found in QPM, with considerably higher tryptophan and lysine content. However, this mutation causes a myriad of other problems in the plant; the seed itself is soft and easily damaged and the plant is less resistant to pathogens. To create QPM, generations of conventional breeding between elite lines and opaque2 mutants have resulted in a type of corn that looks and behaves much like it’s original counterpart but contains all eight essential amino acids at levels optimized for human nutrition.
Dr. David Holding, an agronomist at the University of Nebraska has developed a Quality Protein Popcorn line, the first of its kind. While the health impacts of QPM have been well demonstrated, very little is known about how the gut microbiome responds to this type of crop improvement. My project, in line with the NFHC mission, is to assess the QPM popcorn for effects on the human gut microbiome and theorize how these effects impact health.
My research team led by Dr. Andrew Benson at the University of Nebraska Food for Health Center aspires to serve as a bridge between agriculture and medicine. Our research is taking advantage of genetic diversity in crop plants to identify components with the potential to alter the human gut microbiome and, as a direct result, human health. These improved crop lines could help reduce instances of microbiome-mediated diseases, such as obesity, diabetes and heart disease.