Sweet Mutations

Scientists work on maize samples.

Sweet Mutations

MU’s South Farm Research Center fields are filled with corn plants. But, not all of these plants are in perfect health.

One of the most effective approaches scientists have to understand biological processes is to study mutants to understand what happens to the plant when these processes fail. Research labs at MU, including the Braun Lab, use the farm to crossbreed plants with different genetics in the hopes of identifying which genes are most important. Some of the plants have discolored leaves or don’t survive to full growth. But, a variety of mutants have already been identified as key players in a corn plant’s sugar partitioning process. This process is called mutant characterization.

Rachel Mertz, a post-doctoral member of MU’s Drought Team, was extracting DNA from the plant leaf tissue and conducting mutant characterization out at South Farm on Wednesday morning. This process is done with a tool that cuts small, circular pieces of tissue from the plant leaf. Her work looks similar to the fieldwork done at Bradford Research Center, but the objective is slightly different.

Instead of collecting root tissue to study the expression of all of the genes in root tips under drought without any idea which ones might be important, Mertz is specifically testing whether certain genes are required to move sugar from the leaves to the roots using mutants with defects in sugar movement. Much remains to be discovered about the genes responsible for sugar movement, however, especially about how these genes respond to drought.

Plants get essential nutrients through photosynthesis. Carbon dioxide and water is converted to sugar, which fuels the plant. These sugars are synthesized in the leaves and transported to other parts of the plants.

Some of these genes have an interesting effect on leaf coloration because the mutations cause the plant to accumulate too much sugar in its leaves. For example, some mutations may cause the leaves to turn purple around the edges while others create a tie-dye appearance on the leaf.

Mertz hopes that her research will identify the chromosomal regions and ultimately the genes that underlie these mutations in corn plants. She believes that this research is important because in order to breed high-yielding plants that will meet the ever-growing global food demand, scientists need to better understand how plants feed themselves.

“Out of the dozen or so genes that we’ve mapped so far, only about a quarter have been genes with obvious roles in sugar movement,” Mertz said. “Three quarters have turned out to be genes that we never would have guessed were important for sugar movement, but are nonetheless critical.”

By figuring out which genes are most important in a corn plant, new varieties of high-yielding or drought-resistant corn can be created. This research helps further similar research in other grasses, such as wheat, rice, oats, millet and sorghum, not just corn.

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