Asked to free associate “light” and “plants,” many people blurt “photosynthesis.” But plant aficionado Joanne Chory has spent the last 30 years zeroing in on a different connection. Unlike animals, plants cannot slither under a rock when heat blares or trot to higher ground when waters rise. They cannot roam the countryside for food nor move outside town if they feel crowded. Plants, in short, cannot pull up their roots.
Instead of searching for better pastures, plants adjust to the challenges of the environments in which they find themselves, and they continue to adapt as conditions change over their lifespans. Their ability to detect and respond to nuances in light plays a crucial role in this endeavor. Perturbations in wavelength and intensity spur events that tailor plant behavior to the situation at hand. If a neighbor shades them, for instance, they grow and bend to find an open patch of sunshine. Their finesse in this enterprise illuminates a question: How does a plant translate information from incoming photons—particles whose nature most humans struggle to understand—into actions that help it survive and thrive?
Chory has focused her career on this conundrum. By conceiving and crafting innovative genetic screens, she has coaxed her laboratory subject, the mustard weed Arabidopsis thaliana, to reveal numerous mechanisms that underlie such remodeling. Honors for her work include the Princess of Asturias Award for Technical and Scientific Research, the Gruber Genetics Prize, and the Breakthrough Prize in Life Sciences. Having harvested a bumper crop of discoveries about how plants modify themselves, she is now applying what she has learned. She and colleagues have embarked on a gutsy project that aims to combat climate change and improve farming productivity.
Unlike many biologists, Chory did not spend her early days dazzled by insect symmetry or peering at flower cells under a microscope. As a child, she devoured books—especially Russian novels and Kurt Vonnegut. “He was one of my favorites. I thought he was funny and quirky. I liked quirky.”
Chory grew up in North Andover, Massachusetts, with her parents and five siblings, including four brothers. They were always giving her a hard time, she says, and she acquired “the thick skin I needed” for working in labs populated with sometimes unwelcoming men.
Her parents’ families had come to the U.S. from Lebanon. Although Chory doesn’t speak Arabic, she’s familiar with foods and swear words. “My mother said she said them only occasionally, but I don’t agree because we [siblings] all know them,” she says. The extended clan formed a tightknit community, whose members spent Sundays together on the beach, swimming and gathering around a campfire. “I got to know my cousins really well, and my uncles were like extra fathers to me,” she says.
Although Chory’s mother didn’t finish high school, she “understood the value of an education,” Chory says, and she had ambitions for her children. When it came time to go to college, Chory chose Oberlin, in distant Ohio, with a desire to break away from her family’s embrace and “see what everyone else had in their life,” she says. “All these kids were talking to their parents about their sex lives on the hallway phone,” Chory says. “My parents were definitely parents, not friends.”
In class, she discovered the wonders of the microbial world. After earning a degree in biology, she went to graduate school at the University of Illinois in Urbana-Champaign, where she joined Samuel Kaplan’s lab and studied a photosynthetic bacterium. There, she blossomed scientifically even though the lab was “full of guys who tested the women,” Chory says. To earn an invitation to join the men for drinks, “we had to do an experiment that they thought was worthwhile. They didn’t do that with each other.”
For her postdoc, Chory pivoted toward plants, which offered an unexplored realm and massive potential, as investigators were just beginning to apply molecular techniques to decipher the functions of the organisms’ genes and proteins. “The plant world was wide open,” she says. “That was the good part. The bad part was it was hard to ask a question. You can’t be very specific if you have no information.”
Chory decided to study the process by which plants transform light signals into growth patterns. She marveled at “how you could turn a photon into a developmental form,” she says.
She joined Frederick Ausubel’s lab at Harvard Medical School in 1984, and decided to work with Arabidopsis thaliana, whose promise was just emerging as an experimental subject that might lend itself to molecular analysis. “There were like seven labs that decided to get serious about Arabidopsis,” she says. Members of these labs got together to discuss their plans, Chory recalls, and Caren Chang, a graduate student (now on the faculty at the University of Maryland), “was the hero of the meeting because she had done two experiments.”
To elucidate the mechanism by which plants respond to light, Chory took a bold approach. After she exposed seeds to a chemical that dings up DNA, she wrapped them in aluminum foil, creating a dungeon, and allowed them to grow. Some, she hoped, would carry defective versions of genes that normally participate in the light-signaling pathway and would ignore the gloom. The experiment’s success has perhaps obscured its audacity: Chory was asking plants to develop in the dark as if they were exposed to light.
As expected, most of the 100,000 seedlings had the spindly, leafless appearance typical of dark-grown plants; they did not contain chloroplasts, the organelles in which photosynthesis occurs. But a few dozen grew short and fat—and their leaves expanded. Furthermore, their chloroplasts began to develop, and the plants displayed gene-activity signatures associated with light-grown plants. Other than a complexion problem—they were pale because they lacked chlorophyll, whose production requires light—they resembled their light-grown brethren in key ways.
These results pointed toward the existence of a single regulator that normally suppresses light-governed genes. The plants that flourished in the dark presumably carry a defective version of this regulator that no longer thwarts leaf development.
The notion that one aberrant regulator could circumvent the light requirement seemed preposterous to many investigators. Some of the skeptics adhered to conventional wisdom, which held that light-stimulated activities depend on sparking, not muzzling, a pathway. Nowadays there’s no bias against cellular control agents that operate by quashing the functions of other molecules, says Chory, “but in the 1980s, I think people hadn’t really thought about it yet.” Based on this work, Chory got a job at the Salk Institute for Biological Studies in La Jolla, California, where she has remained since 1988.
Through a similar genetic screen, she found that a hormone in the brassinosteroid family operates in a pathway that connects light with physiological responses. This class of hormones is widespread among plants and Chory’s studies helped establish its members as crucial promoters of growth and development. She eventually unveiled the entire pathway—from the cell-surface molecule that detects the brassinosteroid to target genes in the nucleus.
Chory found other ways in which plants deploy hormones to optimize their shapes and sizes, in part by unearthing relationships with proteins called phytochromes, which sense the intensity, color, and other aspects of light and help plants adapt quickly when their environment changes. “These photoreceptors tell other genes what to do.”
If neighbors are encroaching on Arabidopsis’s light source, for instance, the shading triggers events that induce it “to grow as fast as it can to get on top of that other plant,” Chory says. By identifying genes involved in this process, Chory worked out, for the first time, a biochemical pathway by which plants make auxin, a hormone that promotes many key growth activities.
A multitude of other landmark studies pepper Chory’s career. She has uncovered the roles of multiple phytochromes, unraveled mechanisms that remove malfunctioning chloroplasts, and probed how damaged chloroplasts subdue nuclear genes that encode chloroplast proteins so cells don’t waste resources making components that broken chloroplasts won’t be able to use.
While Chory has directed impressive amounts of energy toward the lab and generated an astounding body of work, she also has carved out time for her family. “I always said this is a great job if you want to be a mother,” she says. Chory appreciates the flexibility that allowed her to attend activities and take a day off to spend with a sick child, although she bemoans the underappreciation of researcher-parent achievement. “You’re not considered macho if you haven’t run a marathon that morning,” she says. “If I get my kid to school by 8 a.m., I want to celebrate that too.”
Chory wants to harness the knowledge she’s generated to give her children a better world, and she aims to reverse climate change. She and colleagues at the Salk Institute are designing and breeding plants that will not only remove carbon dioxide from the air, but will also trap it underground.
Plants excel at sucking up this pollutant from the environment, yet some of the atmospheric relief is short lived. Photosynthesis puts carbon dioxide into sugars, and when the plant dies, they decompose and release the greenhouse gas back into the air. Chory and colleagues aim to capture carbon, siphon it into a chemical that won’t break down, and bury it. They intend to exploit a stable, carbon-laden compound called suberin, which roots naturally make.
Eventually, they hope to breed crop variants with extra roots that run especially deep and overproduce suberin; the team already has pinpointed genes that confer these three traits. If successful, the venture will create seed variants that can offer farmers good yields while sequestering carbon from the atmosphere and making the soil more fertile. The initiative thus promises not only to counteract carbon dioxide emissions, but also to enhance food production for the planet’s burgeoning population.
Chory is optimistic. “I’m here today as a character witness for plants,” she said in a TED talk. “All we have to do is give them a little help and they will go and get a gold medal.” Given her proficiency at gleaning plants’ secrets, they could hardly have a more credible proponent.
Author: Evelyn Strauss, Ph.D.