MIT aims to reduce emissions | Crops

“Our team’s research seeks to address two connected challenges – first, the need to reduce greenhouse-gas emissions produced by agricultural fertilizer; Second, the fact that yields from many current agricultural crops will reduce the effects of climate change on plant metabolism, “said Christopher Voigt, the project’s faculty lead and a professor in the department of biological engineering at MIT.

“We’re pursuing six interdisciplinary projects that are each key to our overall goal of developing low-emissions methods for fertilizing plants that are bioengineered and more resilient and productive in a changing climate,” he said.

Mary Gehring and Jing-Ke Weng are also associate professors in the department of biology at MIT. They ‘ll lead two of the projects.

For most of human history climate change has been gradual – through hundreds or thousands of years. That pace allowed plants to adapt to variations in temperature, precipitation and atmospheric composition. But human-driven climate change has occurred more quickly, and crop plants have suffered. Crop yields have declined in many regions.

“If we want to ensure an abundant supply of nutritious food, we need to develop basic mechanisms for bioengineering a wide variety of crop plants that will be both hearty and nutritious in our changing climate,” Gehring said.

In previous work she has shown that many aspects of plant reproduction and seed development are controlled by information outside of the deoxyribonucleic-acid sequence. She has been using research methods she has developed to identify ways to create varieties of seed-producing plants that are more productive and resilient than current food crops.

While it is possible to develop plants that integrate robustness-enhancing traits by combining dissimilar parental strains, scientists are still learning how to ensure new traits are carried forward from one generation to the next.

“Plants that carry robustness-enhancing traits have ‘hybrid vigor,’ and we believe that perpetuation of those traits is controlled by epigenetics,” Gehring said. “Some food crops – such as corn – can be engineered to benefit from hybrid vigor, but Those traits are not inherited. That’s why farmers are growing many of today’s most productive corn varieties and plant new batches of seeds each year. Moreover many important food crops have yet to realize the benefits of hybrid vigor. “

The project that leads to Gehring – “Developing Clonal Seed Production to Fix Hybrid Vigor” – aims to create food-crop plants that are both more robust and genetically identical to their parent. So they’d be able to pass beneficial traits from generation to generation.

The process of clonal – or asexual – production of seeds that are genetically identical to the external parent is called apomixis.

“Because apomixis is present in 400 flowering-plant species – about one percent of flowering plant species – it is probable that genes and signaling pathways are necessary for apomixis already present within crop plants. Our challenge is to tweak those genes and pathways so that the reproduction of plant switches from sexual to asexual. “

This project will leverage the fact that genes and pathways related to autonomous asexual development of the endosperm exist in the model plant Arabidopsis thaliana. In previous work on Arabidopsis, Gehring’s team researched a specific gene that, when misregulated, drives development of an asexual endosperm-like material.

“Normally that seed is not viable,” she said. “But we believe that by the expression of epigenetic tuning of the additional relevant genes, we will be able to retain the plant that material – and help achieve apomixis.”

If Gehring and his colleagues succeed in creating a gene-expression formula for introducing endosperm apomixis into a wide range of crop plants, they will be made a fundamental achievement. Such a method could be applied to create and perpetuate all-farm new crop breeds capable of withstand their changing environments while requiring less fertilizer and fewer pesticides.

“Self-fertilizing” crops created

About a quarter of greenhouse-gas emissions in the United States are a product of agriculture. One third of those emissions are for fertilizer production and use accounts. The emissions include nitrous oxide, which has a heat-trapping capacity 298-fold larger than carbon dioxide, according to a 2018 Frontiers in Plant Science study.

Most artificial-fertilizer production also consumes huge quantities of natural gas and uses minerals mined from nonrenewable resources. Much of the nitrogen fertilizer becomes runoff that pollutes the waterways. For those reasons the Climate Grand Challenges project aims to greatly reduce the use of human-made fertilizers.

One approach is to cultivate cereal-crop plants. They account for about 75 percent of global food production. They’re capable of drawing nitrogen from metabolic interactions with bacteria in the soil. Weng leads an effort to genetically bioengineer crops such as corn, rice and wheat to create their own fertilizer through a symbiotic relationship with nitrogen-fixing microbes.

“Legumes can form root nodules through which they receive nitrogen from rhizobia bacteria in exchange for carbon,” Weng said. “That metabolic exchange means legumes release far less greenhouse gas – and require far less investment of fossil energy – than do cereal crops, which use a huge portion of artificially produced nitrogen fertilizers used today.

“Our goal is to develop methods for transferring legumes'” self-fertilizing “capacity to cereal crops. If we can revolutionize sustainability of food production. “

The project – “Mimicking legume-rhizobia symbiosis for fertilizer production in cereals” – will be a five-year effort. It draws on Weng’s studies of metabolic evolution in plants. It has identified molecules related to formation in root nodules that permit exchange between legumes and nitrogen-fixing bacteria. He also has reconstituted specific signaling and metabolic pathways in plants.

Weng and his colleagues will decipher the spectrum of small-molecule signaling processes that occur between legumes and rhizobium bacteria. Then they will be genetically engineered into an analogous system of non-legume plants.

Using metabolomic methods they will then identify which small molecules are excreted from the legume roots prompt a nitrogen-carbon exchange from rhizobium bacteria. Finally, they’ll be genetically engineered to biosynthesis those molecules in non-legume plants and observe their effect on the rhizobium bacteria surrounding the roots.

While the project is complex and technically challenging, its potential is staggering.

“Focusing on corn alone, this could reduce production and use of nitrogen fertilizer by 160,000 tons,” Weng said. “And it could halve the related emissions of nitrous-oxide gas.”