While plants can't see, they can sense sunlight via an impressive array of photoreceptors. These light-sensitive molecules detect environmental cues—like sunlight—that plants use to make "decisions" about their growth and development, such as when to germinate and flower. Research by plant biologist Joanne Chory is uncovering the signaling pathways plants use to detect changes in the sunlight that they receive, not only when seasons change but also when they grow in shady, crowded conditions. Her research may eventually spur the development of ways to modify plants' response to sunlight, a discovery that could increase the yields of agricultural crops.
Using molecular and genetic tools, Chory, working with Pablo D. Cerdán at the Salk Institute, recently identified a gene, pft1, and characterized a signaling pathway that explains how some plants adjust their growth and flowering to shade. Their studies showed that pft1 and the light-sensing molecule known as phytochrome B are part of a signaling pathway that is distinct from the pathway involved in sensing the length of daylight. The findings have potentially great significance for commercial farmers, who typically plant their crops so close together that they must compete for light. With an understanding of pft1's role, it may be possible to develop plants that still flower and set seed, even under shady conditions.
"Few people realize that the biggest competitor for plants is other plants," Chory said.
When plants perceive that they are not getting enough sunlight to thrive, they undergo a series of developmental changes, like making longer stems and fewer leaves, all in an effort to soak up more sun. If that fails, they resort to flowering early, producing a "desperation" flower to ensure the survival of at least some offspring.
Chory's model is Arabidopsis, a small plant that is easy to grow, prolific, and has the smallest genome of any flowering plant. In earlier research, she studied 141 varieties of Arabidopsis gathered from around the world and found that the genetic variation in key photoreceptors may explain how they can fine-tune their responses to light. This variation ensures that plants in northern climes near the poles, for example, are more sensitive to light than their counterparts closer to the equator.
Work in Dr. Chory's lab has also led to the discovery of a steroid hormone, brassinolide, which controls plant development in response to light, and has identified the plant steroid receptor and signaling pathway. She has also been very active in The 2010 Project, a multinational effort begun in 2000 to determine the function of all the genes and proteins in the plant, Arabidopsis. "The project's goal is to understand all the genes of Arabidopsis. This is the only way we are going to understand what makes a plant a plant," Chory said.
At the Salk Institute, Chory oversees the work of postdoctoral fellows, Ph.D. students, and undergraduate students who do research in her laboratory. Each summer, about six high school students join her laboratory through a Salk Institute outreach program. Chory enjoys working with students at all levels. "I devote my time to mentoring students because I feel strongly that there's nothing like the joy that comes with making a new discovery, even if it's a small one," she said.