• Claire Benjamin

Pat Brown: Shedding new light on sorghum

Sorghum thrives in dry, arid climates that are ill suited to corn and provides an alternative source of biomass for sustainable fuel production.

But first, scientists will have to exploit its capacity for growth.

“Sorghum is processed in the same ethanol facilities that use 40 percent of our corn crop,” said Pat Brown, an assistant professor at the University of Illinois, a member of the Energy Biosciences Institute, and a member of the Genomic Ecology of Global Change research theme at the Institute for Genomic Biology. “It’s just as good for making ethanol as corn is—there’s no difference in conversion efficiency.”

Having evolved on the edge of the Sahara Desert, sorghum thrives in sandy soils and hot temperatures. “For thousands of years, it’s been progressively adapting to a more harsh and arid environment,” Brown said. “It looks like that’s going to be really important when you look at the predictions of how we are going to have to produce more food from the same amount of land, with more unpredictable rainfalls and rising temperatures.”

Today, the Sorghum Belt stretches from South Dakota to Texas. But in as few as 50 years, the climate in Central Illinois may be like the climate today in Central Texas—which could make sorghum the crop of choice in more places.

“That’s not that far down the road,” Brown said. “Considering all of these factors, I think it’s going to be really important to understand how sorghum does it.”

So Brown is hunting for the genes inside sorghum that could be useful for bioenergy production, like plant height and flowering.

Flowering stops vegetative plant growth so the plant can divert nutrients to seed production. By impeding flowering, scientists can force the sorghum plant to continue to grow and produce more biomass.

“We are trying to understand the different signals that get integrated so that the plant knows when to flower,” Brown said. “We want it to remain in a vegetative state, putting out leaves and getting taller and taller.”

So far, Brown and his colleagues have identified promising regions of DNA through “genome-wide association” where researchers compare small changes in the DNA of different sorghum plants to see which genes cause which physical characteristics.

Through this process, they have found a change that is likely associated with sorghum’s flowering time. Their hypothesis looks promising because the closest gene to this DNA variation is the same gene that controls rice plants’ photoperiod response, the process by which plants can tell the time of year by sensing changes in the length of each night.

“We have not proved that it’s doing the same thing in sorghum, yet,” Brown said. “But it’s a result that we are pretty excited about. It’s an obvious candidate.”

Brown received his bachelor’s degree from Reed College. For his undergraduate thesis, he studied lichen, the result of a symbiotic relationship between fungi and either algae or cyanobacteria.

Back then, he was intrigued by organisms’ physiology. But after working with a maize geneticist at the University of California, Berkeley, he realized that his physiological questions could be answered through genetics.

Brown went back to school to earn his doctorate in plant genetics from Cornell University. He began studying sorghum for his PhD and continues to study the crop today because, unlike corn and soybeans, there’s a lot of basic knowledge still to learn.

“It’s exciting because there’s not as many people working on it,” he said. “There is a lot of stuff to work out.”

This article originally appeared in March 2014 the Carl R. Woese Institute for Genomic Biology newsletter.