As a Harvard Medical School postdoc in the 1980s, Joanne Chory tried to grow plants in the dark. Since they can’t photosynthesize without light, the seedlings didn’t grow very well. Most didn’t form leaves, and they didn’t produce chlorophyll, making the sprouts white instead of green. Not all of Chory’s plants were duds, however. Some grew as if they were bathed in light. Because Chory was trying to understand how plants respond to light, these seedlings were exactly what she was looking for. And as it turned out, they would shape her career trajectory and revolutionize our understanding of plant biology.
Eager to understand how the plants grew despite living in darkness, Chory and her colleagues analyzed the expression of all the genes then known to be associated with light, and found that the genes were turned off in the dark, as they are in normal plants. Digging deeper into the plant’s genetics, the researchers deciphered that the development of the plants that grew in lightless conditions was driven by a mutation in a little-studied gene that the team called de-etiolated 1, or DET1. Chory continued to study this gene for a couple of years at Harvard and then in her own plant genetics lab at the Salk Institute. Eventually, she and her colleagues determined that DET1 coded for a previously unknown receptor in the signaling pathway that determines how plants respond to light.
This was a puzzling result, because the only light-related receptors known to exist in plants at the time were phytochromes, a class of photoreceptor. Many plant biologists were skeptical of the existence of a new light receptor, Chory says. “I did my genetic screens and went to a meeting [to present the results], and they were all looking at me like, ‘Who are you?’” she says. She got to work demonstrating the robustness of her research. Over the next decade, she and her collaborators cloned DET1 and showed that it was expressed in the plant cell’s nucleus, and that its encoded protein (conserved in animals as well as plants) indeed played a role in light-regulated gene expression.
Studying how plants interact with light “turned out to be a great research question,” says Chory. “You can have a big long career and not even be halfway done.”
Learning to love plants
Born in Boston in 1955, Chory grew up with four brothers and a sister. “Labs always were comfortable for me because you had to get along in a big family, and you have to get along in a lab too,” she says.
While Chory excelled at math and science in school, she says she didn’t know growing up that she wanted to be a scientist. A genetics course in college sparked her interest in research, she says. She earned a bachelor’s degree in biology from Oberlin College in Ohio in 1977 and a PhD in microbiology from the University of Illinois Urbana-Champaign in 1984. During grad school, she studied the development of membranes in the photosynthetic bacterium Rhodobacter sphaeroides in Samuel Kaplan’s lab. Looking back, she says, studying photosynthesis may have drawn her attention to plants, but Chory’s main goal when searching for a postdoctoral position was to seek out a challenge, particularly in studying the genetics of more complex organisms. She looked at three labs studying Drosophila and three studying plants, and ultimately chose to work with plant researcher Fred Ausubel at Harvard Medical School.
Ausubel was studying Arabidopsis thaliana, a flowering plant also known as thale cress. It grows fast, taking as little as six weeks to germinate and form mature seeds, and it has a small genome of only around 135,000,000 base pairs. It’s also a small plant, which made for easy cultivation in Ausubel’s lab, located at Massachusetts General Hospital in downtown Boston, far away from any fields. “We had to do everything inside,” says Chory. “[Arabidopsis] was a good plant for that.” She recalls labs with walk-in areas filled with experimental plants, on which she and her colleagues would conduct genetic screenings by analyzing thousands of seeds in big Petri dishes. Within a couple of years, Chory made her seminal discovery that mutant Arabidopsis grew in the dark.
Around the time that Chory was conducting research on DET1 mutant plants, she met Stephen Worland in the bar of the Cold Spring Harbor Laboratory (CSHL). Both were visiting the research facility, and at the bar, they started chatting. Worland was finishing his PhD at the University of California, Berkeley, and soon afterward moved to Boston to become a postdoc at Harvard Medical School. The two continued seeing each other, married in 1987, and then moved to California, where Chory became an assistant professor at Salk in 1988 and an associate professor in 1994. Later, they adopted two children: Katie in 1995, and Joe in 1997.
At Salk, Chory continued to work on DET1 and on Arabidopsis plants with a slightly different genetic alteration: a mutation in the related DET2 gene. Her experiments with this mutant led her to the discovery that plant hormones called brassinosteroids are associated with light signaling. While brassinosteroids had been discovered in the 1970s, their role in growth and development was unclear. Work by Chory and others confirmed that brassinosteroids are a distinct class of hormones that help control light-regulated plant development. Over the next 15 years, Chory uncovered the entire pathway by which this takes place, from the activation of receptors in the plant cell membrane to the hormones’ effects on transcription factors in the nucleus.
“It really cannot be overestimated how huge a contribution that is. It’s really at the very highest level,” says Detlef Weigel, an evolutionary biologist at the Max Planck Institute for Developmental Biology and one of Chory’s longtime collaborators. “If this discovery had been made not in the plant system, but in the animal system, it certainly would have been honored with a Nobel Prize.”
Chory has also studied how the biosynthesis of auxin, a key plant hormone that helps regulate growth and development, is necessary for plants to find sunlight and avoid shade in order to grow. “Plants really have to look at light for information,” she says. “They know where they are on the Earth based on the color of light. . . . They can tell you when the middle of the day is versus the end of the day based on the color of the red and far-red part of the spectrum, and they know when it’s morning because there’s a lot of blue light in the spectrum. Plants are very attuned to the light environment.”
Tending to seedlings
“Joanne is probably the most influential plant biologist of the modern era,” says Steven Kay, a molecular geneticist at the University of Southern California in Los Angeles, who has collaborated with Chory on circadian clock-associated pathways in plants. “She’s an incredibly rigorous scientist. . . . But at the same time, she brings with that an incredible warmth and commitment to collegiality and to training.”
Chory has mentored numerous students in her lab at Salk and as an adjunct professor at the University of California, San Diego (UCSD), over the last three decades. She estimates that around 20 graduate students and 120 postdocs have worked for her. Jennifer Nemhauser, a plant biologist at the University of Washington who was a postdoc in Chory’s group for more than five years, says the lab was filled with “super ambitious, super smart, really committed and generous scientists. . . . There were so many different journal clubs going on, and it was just a hive of intellectual exchange.” As a result, Nemhauser ended up postponing a job offer for six months “because I was having so much fun. . . . I was still learning so much that I wanted to stay and learn more.”
One of the learning opportunities that Chory offers her trainees is the freedom to try new techniques in the lab as technology advances. “I was one of the first people in Joanne’s lab to do RNA sequencing, and she was super supportive,” says Ullas Pedmale, a plant researcher at CSHL who was a postdoc in Chory’s lab from 2009 to 2015. “[When] people come to me [and say] ‘I want to try this,’ initially I’ll be apprehensive. . . . Then I think, Joanne was supportive; we should let people explore their ideas.”
“She’s so proud of the people that she has trained and is very happy to let us think that we have come to our remarkable insights completely on our own, even though she’s actually been in the background,” Nemhauser notes. And, she adds, Chory’s mentorship extends beyond her own lab: “If she’s at a meeting, she goes to the poster session and talks to trainees. I can’t even tell you how many people have told me that one interaction like that at a meeting made the difference to them in how they saw themselves as a scientist.”
Yunde Zhao, a former postdoc in Chory’s lab who is now an auxin researcher at UCSD, agrees. “A lot of times people know the scientific contributions, but don’t know the other part of an education, [which is] how you treat people,” Zhao says. “She promotes the whole field, she is not selfish. . . . She has so many contributions [beyond] just scientific discoveries.”
Big challenges, big ideas
Chory’s path to success hasn’t always been easy. In 2004, she was diagnosed with the progressive nervous system disorder Parkinson’s disease. For a decade after that, she says she barely had symptoms, but in the last few years—especially in the last twelve months—the disease has gotten progressively worse. She’s on medication that raises dopamine levels, which decrease during the disease due to a loss of neurons, and a few years ago she received a deep brain stimulator, which delivers electrical pulses to relieve symptoms such as muscle tremors. It “makes you more even throughout the day, so that you’re not having these ups and downs,” she says.
Still, she says she has good days and bad days. “When you wake up, you don’t know what kind of day you’re going to have until you try to get out of bed . . . And then when you have a good day, you try to do too much.” The disease has taught her to live for the moment, she says. “I do take risks now that are much bigger,” especially when it comes to her science.
Her latest big project is leading the Harnessing Plants Initiative, a project made up of five teams of plant biologists at Salk that are attempting to fight climate change by engineering plants to take in more carbon dioxide through their roots. “I wanted the challenge of working on something totally new to me,” she says. The project has three main components: getting plants to grow more roots, deeper roots, and roots that have more suberin, a decomposition-resistant compound found in cork that is good at capturing carbon. Chory and her colleagues have found genes in Arabidopsis that can be knocked out or overexpressed to make plants grow more roots and are working on the other two characteristics, with the ultimate goal of changing these traits in crop plants. Right now, they’re working on inserting the root-altering genes into the canola plant (Brassica napus), which is closely related to Arabidopsis.
But engineering crops to take in more carbon dioxide won’t be enough to slow climate change, Chory notes. “We have to make policy change so that farmers can be incentivized to buy these seeds.” With the right policies in place, the initiative would be able to take advantage of the existing agricultural system to keep the price down compared to machine-based carbon sequestration processes, she says.
The initiative receives funding from TED’s Audacious Project, a program that supports ambitious ideas aimed at solving pressing issues. “It was definitely very audacious when I proposed it to [TED],” she says. “It seemed like an alternative no one had really ever suggested in the whole climate world.” Chory says it came to her and her colleagues because “we were all plant geneticists—we looked at plants differently.”
Chory presented the initiative’s ideas to the public in a TED Talk last year during an event announcing several projects funded by TED’s Audacious Project. She describes presenting as “nerve-wracking,” but is happy that the initiative’s ideas have reached so many viewers—more than a million so far. “Every one of [the winning projects] really benefited a lot from it. Those are the TED Talks I like the best, the ones of people trying to find solutions,” she says. “ We just want to be part of the solution.”
Emily Makowski is a freelance writer based in Boston. Find her on Twitter @EmilyRMakowski.
Correction (March 10): The size of the Arabidopsis genome has been changed from 135,000 base pairs to 135,000,000 base pairs. The Scientist regrets the error.