Elizabeth Nelson
Elizabeth Nelson

Micronutrients on the Cob

by Jackie Swift

“Plant breeders are the engineers of plant science,” says Michael A. Gore, School of Integrative Plant Science, Plant Breeding and Genetics. “Engineers produce something useful to society, an end product, such as a bridge or computer software. In the same way, plant breeders produce improved crop varieties. Maybe we’re improving a crop’s adaptation to climate change or increasing its nutritional quality. And by disseminating seed of that improved variety throughout the world, we’re able to have impact.”

Having impact and understanding the biological rules of life are central motivations for Gore. Those twin passions come together with force in his current project: to create an open-source digital ecosystem to optimize food crops, starting with maize. Better known as corn in the United States, maize is one of the world’s most important crops in terms of nutritional value and economic significance.

Gore envisions a powerful tool that plant scientists and other researchers can use to make better, more strategic decisions about plant breeding and selection. To carry out the project, Gore has joined with Kelly R. Robbins, Plant Breeding and Genetics, and Ying Sun, Soil and Crop Sciences, both at the School of Integrative Plant Science; Noah Snavely and Abe Davis, Computer Science; and collaborators from the Agricultural Research Service of the United States Department of Agriculture (USDA), as well as scientists from other universities. The project is funded by a $1 million grant from the National Institute for Food and Agriculture, an agency of the USDA.

A Big-Picture, Collaborative Approach

Gore and his collaborators seek to integrate all the data they can gather about each crop variety’s observable, phenotypic traits. The team will leverage state-of-the-art data sources, including aerial drones, ground rovers (subcanopy robots that roam through farm fields), high-resolution satellites, and mobile apps. Then they will develop software that analyzes the data using process-based and statistical models to forecast yield over the growing season and to make other crop predictions.

“This is a radical, multidisciplinary collaboration,” Gore says. “We have computer scientists, a statistical geneticist, and a crop modeler. Then there’s me and my lab. We are technically plant biologists and geneticists, but we’ve been collaborating with engineers for a while now and we think like engineers. We are hypothesis driven, but at the same time we approach science as an engineering question or challenge, where we go through the cycle of design-build-test-learn.”

As one of its first steps, the research team is exploring methods for integrating aerial data from drones and merging them with ground rover data. “By [merging drone and ground rover data], we will have two different perspectives of a plant’s life history,” Gore explains. “If we’re able to use multiple data points over the growing season, then we’ll be able to model the crop’s growth and development over its life cycle. We’re studying maize right now, but these approaches can be used for a number of different crop species.”

“We approach science as an engineering question or challenge, where we go through the cycle of design-build-test-learn.”

Crop breeders and modelers anywhere in the world will be able to use the technology and data generated by the project to support their own research and breeding.

Genes behind Provitamin A

Gore is dedicated to improving the nutritional quality of crops. Worldwide, more than two billion people suffer from deficiencies in vitamins and minerals, he explains. In some cases, people depend on foods that provide energy but lack micronutrients, leading to a condition called hidden hunger.

Often, the effects of such a diet are not immediately apparent. But hidden hunger can have profound consequences. For example, deficiency in vitamin A is the leading preventable cause of childhood blindness in developing nations. An estimated 127 million preschool-age children and 7 million pregnant women around the world are at risk of vitamin A deficiency, and 650,000 preschool-age children die from it every year.

Galvanized by these statistics, Gore and some colleagues went in search of the genes that produce carotenoids—pigments that give plants bright yellow, red, and orange colors. The human gut converts provitamin A carotenoids to vitamin A.

In a genetic mapping experiment involving a maize population of nearly 5,000 genetically distinct lines, the researchers concluded that the variability of carotenoid levels in maize seed depended almost entirely on only 11 genes.

“The maize genome has something like 30 thousand genes, but only these 11 are important when breeding for these carotenoid traits,” says Gore. “Breeders now know where to focus their attention. They just have to figure out the optimal combination of these [11 genes] to reach the level of provitamin A they want the plant to produce in seed.”

Opening a New Door to Vitamin E Research

The Gore lab has used the same maize population of nearly 5,000 distinct lines to identify the genes responsible for the production of tocopherol (vitamin E) in seed. They discovered that the production of vitamin E is genetically linked to chlorophyll production in the embryo of maize seed. “That was a startling finding because maize seed is non-photosynthetic—it’s non-green—so you wouldn’t expect it to have chlorophyll or for that chlorophyll to contribute to the production of tocopherol,” Gore says.

At first, Gore and his colleagues struggled to understand the implications. “When you see results like that, your first reaction is to say, ‘I don’t know what it means,’” Gore says.

Gore turned to a longtime collaborator, the biochemist Dean DellaPenna (Michigan State University). DellaPenna has been working for years on the chemical pathway that controls vitamin E production in plants. “Working with DellaPenna, we were able to put this story together,” Gore says. “We think of it as a cycle where there’s a phytol group that’s part of the chlorophyll molecule. This phytol group is enzymatically released, then used by the plant in the production of tocopherols.”

The link between vitamin E and chlorophyll production in the embryo of maize seed is tied to the action of two genes, por1 and por2. These findings have opened a new door for research into vitamin E production in other cereal crops. “It’s likely that vitamin E production in these other crops is genetically driven, as it is in maize, and that these other crops have por genes that are evolutionarily related to the ones in maize,” Gore says. “If other researchers can genetically identify and characterize the genes, they should provide a mechanism for breeders to increase the production of tocopherols in many crops.”

Other projects based in Gore’s lab are investigating the genetics of B vitamins, iron, and zinc in maize seed.

From Morgan Horses to Plant Biotech

Gore grew up on a Morgan horse breeding farm, where he was immersed in genetics from his earliest childhood. “I spent my junior and senior high school years poring over pedigrees trying to figure out which stallion was the best sire to cross with our mares,” he remembers.

He began his undergraduate work as a pre-vet major. Then he heard a lecture on plant biotechnology. “It shook me to my core,” he says. “It resonated with me so deeply, I changed my major the next day to plant biotechnology. I knew that was my place in the world. That was how I could best contribute to improving society and providing something to humanity.”

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