Harvesting an Interest in Genetics
For corn geneticists like Ben Julius, fall means one thing: harvest time. Although the hard, dry ears of corn that Julius picks are not meant for consumption, he hopes one of these ears holds the secret to the mouthwatering sweet corn Missourians look forward to each summer.
“The reason sweet corn is sweet is because of a process that allows the plant to move sugar out of its leaves to other parts of the plant, including the ears,” says Julius, who is a doctoral candidate in the Division of Biological Sciences. “What genes allow this sugar movement to work properly is the question we’re hoping these ears will tell us.”
Unlike large commercial farms that use a combine to bring in the season’s haul, harvesting corn for research can be slow going. It involves walking up and down rows and rows of corn that, to the untrained eye look identical but, in fact, each row is a genetically distinct family. The corn plants that make up each row also look like your typical end-of-the-season corn plants – tall, drying – with the exception that quite a few have brown bags covering an ear.
“Each of these ears is the product of a specific hand-pollinated cross, one of hundreds of crosses I did earlier in the summer,” Julius explains, pointing to the writing on the paper bag that indicates the ear’s parentage.
As he walks, Julius stops at each of these marked ears. He removes the bag, tears the ear off the stalk, peels back the husk, puts the ear back into the bag, and places it into a red mesh sack. When he gets to the end of a row, he cinches the red sack closed and drops it to the ground. He then proceeds up the next row – one of about 400 he has yet to walk before he’s done.
The relative speed with which Julius proceeds through the rows and his general comfort among the towering plants would suggest a pastoral upbringing. Nothing could be further from the truth, Julius says with a laugh.
“I grew up in south St. Louis,” he says. “The only time I encountered rural life is when we’d go on camping trips as a family.”
While he traces his original interest in genetics back to his favorite childhood movies Jurassic Park and Teenage Mutant Ninja Turtles, he says he discovered his passion for corn genetics while doing research as an undergraduate at Truman State University with Prof. Diane Janick-Buckner and Prof. Brent Buckner.
“It was the Buckners who gave me my first exposure to research, and the more I got into it, the more I loved it,” he says. “It ended up being a combination of really enjoying genetics and science, having that first exposure to research in corn genetics, and also realizing that what I’m doing will help people in the future.”
As a graduate student, Julius is investigating the genes that control sugar transport in corn. He’s carrying out his research in the lab of David Braun, a professor of biological sciences.
“A plant makes its own food, and that food is sugar,” explains Julius, who is also a member of MU’s Interdisciplinary Plant Group. “It converts sunlight, water, and carbon dioxide into sugar through photosynthesis. This happens in the leaves. It then has to move, or transport, that sugar from the leaves out to rest of the plant via the vasculature system.”
Julius likens a plant’s sugar transport system to our modern highway system, complete with on and off ramps and bridges. If the highway is not properly built or faulty, he says, it slows down or stops traffic. A “traffic jam” along this sugar highway can have many detrimental effects for a plant.
“First off, sugar is the main energy source for cell division and any kind of activity going on in the cell. If a plant doesn’t have that energy, it can’t grow,” Julius says. “It’s also very important in signaling for certain processes in the plant to be turned on or off. A backup in sugar transport disrupts how much sugar should be in a certain area of a cell or tissue at any given time. If that whole process is thrown off, then all the signaling and everything the signaling controls is thrown off as well.”
Physiologically, plants with a problem transporting sugar tend to be small and weak looking. A backup of sugar also will cause a plant’s leaves to turn pale yellow or red. Identifying these plants out in the field, Julius says, is one way he identifies the underlying genes involved.
“Once we identify them, we do some genetic analyses to determine what specific genes are different and then try to figure out what those genes do,” he explains. “Basically, we break the plant to figure out what the thing we broke does.”
In some cases, he says, he starts with a gene he thinks may be involved with sugar transport and “turns it off” to see what impact it has on the plant’s ability to move sugar. Genes that he’s using this so-called reverse genetic approach on are called, appropriately enough, SWEETs. He recently used CRISPR-CAS9 technology to generate plants with changes in three of these SWEET genes. He believes these genes may be involved early on the process, when the sugar molecules are being moved into the veins.
“The sugar molecules are made in the bundle sheath and mesophyll cells in the leaf and they have to be moved from those cells into the vascular cells, but there is a little gap or bridge that needs to be crossed from the cells where the sugars are made into the vasculature cells. We believe the SWEET genes function in this gap,” he explains.
He says that ultimately understanding the genes that control sugar transport will allow scientists to engineer corn plants with improved yield and greater tolerance to drought and pests.
After Julius harvests all the corn ears, he will spend many hours shelling the ears. He stores the kernels in specially barcoded yellow envelopes in a cold room in the Ernie and Lottie Sears Plant Growth Facility.
“We do this so we can grow the exact plant if we need to in a future year,” he explains as he twists a dried ear through a corn sheller.
He says these seemingly tedious steps are all part of the larger research endeavor and have their payoffs in the end.
“Being a part of a process that is discovering something new and contributing that new piece of the puzzle to the larger picture of how nature works – that is my favorite thing about doing research,” he says.
Julius has had many opportunities to talk to farmers who have benefited from innovations that have come about from research like his. Seeing that impact, he says, is why he plans to pursue a position with a biotech company when he’s done with his graduate work.
“My goal is to help people, and I feel like industry is out there on the frontlines with farmers,” he says. “And that’s where I want to be.”
(All photos by Melody Kroll.)