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Next generation: A marriage between labs nurtures the seeds of discovery

Zuyu Zheng and Yongxia Guo

Pale green seedlings of arabidopsis thaliana have emerged from the soil. They stretch toward the artificial light in the Salk growing room, ready to flourish. Then Zuyu Zheng installs a shade device above the young plants, limiting their light. What will the seedlings do? Because survival instincts are strong, the plants immediately begin growing faster, searching for life-giving light. Faced with adversity, they exhibit resilience.

That’s a trait shared by both Zheng and his wife and research partner, Yongxia Guo. Together, they study plants in adverse situations, tenaciously seeking to understand the mechanisms by which plants adapt and survive. The work can be littered with obstacles.

“That’s why they call it research,” says Zheng, a postdoctoral researcher in Salk Professor Joanne Chory’s laboratory. “You search and then you research. It can be frustrating, but you can’t give in.” The interest in plants comes naturally. Both Zheng and Guo were raised on family farms in central China.

“Our parents grew corn and wheat,” says Zheng, “and we had a vegetable garden. So learning about plants was important.” Today, however, those family farms no longer exist. Like so many agricultural enterprises around the world, they’ve fallen victim to urban sprawl.

“People don’t realize how much arable land is giving way to development,” says Guo, a postdoctoral researcher in Salk Professor Joseph Noel’s laboratory. “More and more, plants are forced to grow in difficult situations, either in poor soil or in greater density. What’s going to happen?”

It’s a critically important question. With the world’s population expanding and arable land diminishing, the research that Zheng and Guo perform directly affects future food supplies. How can they help plants compete for light in dense populations while in poor soil? How can they engineer plants that are more resilient?

Their solution: collaboration. It’s a partnership they’ve been perfecting since they first met as students at Henan Agricultural University in Zhengzhou, China. Since 2008, they’ve been at the Salk Institute, working in separate labs but together. “Our labs have a tradition to collaborate,” Guo explains, “so that was good for how Zuyu and I work.”

Chory, professor and director of the Plant Molecular and Cellular Biology Laboratory, recalls how Zheng and Guo advanced her lab’s research into how plants outcompete nearby rivals for sunlight by making more of the plant hormone auxin.

“Zuyu performed a simple, yet elegant, genetic screen from which he identified an enzyme, an aminotransferase, that not only regulated levels of auxin, a growth hormone, but also regulated ethylene, a different plant hormone,” says Chory. “This is one of the first examples of direct metabolic coupling. Zuyu and Yongxia then took these studies from a genetic screen, through protein purification and X-ray crystallography. They make a very nimble and multi-talented team.”

Such teamwork spills into their personal lives. They talk about their work at home–a lot, both admit. The ongoing conversation has led them down paths of discovery and produced a number of published papers. One paper describes how a dying plant generates a chemical message for the next generation, alerting dormant seeds to sprout after a fire. Another, related to their current shade response studies, offers a new understanding of how hormones regulate growth.

“But there are still so many questions to be answered,” says Zheng. So the dinner conversations will continue.

As much as possible, though, free time is family time, spent with their two children, Emily, eight, and Eric, six. Together, they hike, play ping pong or challenge each other to games of chess. Not surprisingly, the children share their parents’ interest in science.

“Eric wants to be a paleontologist,” says Guo, “so he can drive a blue Jeep and wear gloves. And Emily lectures him on her hypotheses about dinosaur extinction. She thinks a volcano erupted and created so much smoke and ash that all the vegetation died. Then the dinosaurs, which were plant-eaters, had nothing left to eat.”

Given the vital connection between plants and survival, back then as well as today, one has to wonder why plant research doesn’t draw more interest–and funding.

“Many people here have never been hungry,” says Guo. “Everyone knows someone who has died of cancer or who has diabetes. But no one here knows someone who has died of hunger. In China, however, people of my parents’ age have confronted their frustration for no food. They remember being hungry. So, in China, plant research is well-funded.”

Zheng adds, “Joanne tells a story of how students at Harvard were asked where bread comes from and they didn’t know. People don’t think about it. They take food for granted.”

“There’s no transgenerational memory,” says Guo.

Zheng adds that, with the support of the National Institutes of Health, their goal is to study–and genetically modify–the mechanisms plants use to adapt to stress.

“We want to keep the plants growing fast but strong and to help them produce a high yield of fruit and seed,” he says.

In the Salk growing room, the tenacity and passion of the two researchers comes readily to light. Noticing a mutant phenotype, Guo immediately bends over a seedling, commenting to her partner on its unique traits. Zheng points out another.

“This one is exhibiting transgenerational memory,” he says, adding that, in response to environmental stress, a plant’s epigenome (chemical changes that modify an organism’s DNA) can actually change so that a future generation is better equipped to handle that stress. It’s essential to adaptation and survival.

In another part of the lab, a researcher is painstakingly examining a dish of tiny seedlings, separating those showing the desired phenotype and transplanting them into soil. The subject is again Arabidopsis thaliana, a model organism that grows rapidly and has its entire genome sequenced. Still, the process is tedious and often frustrating.

“You have to zigzag and always look for another approach, another way to get to the answer,” says Guo.

“Most experiments fail but you can’t give up,” adds Zheng. “You hope that one day you will find something important for the field and that it will change people’s quality of life. This kind of hope keeps me going.”