How do plants move?

Award-winning University of Missouri plant geneticist moves closer to answering Darwin's 120-year-old question

In 1880, Charles Darwin described how plants—though firmly rooted—moved in response to light. This, he proposed, allowed plants to maximize photosynthesis. But how do plants move? Darwin never found the answer, but a University of Missouri-Columbia researcher has moved much closer to solving the 120-year-old mystery, which could lead to advancements in plant growth.

"Plants can't run or jump, but they can move," said Mannie Liscum, an assistant professor of biological sciences. "By gaining a better understanding of phototropism, or the bending of plant organs in response to light, we can improve how plants grow and develop."

Liscum and his research team study Arabidopsis, a small flowering plant that is in the same family as cabbage and radish. Plant scientists worldwide study Arabidopsis as a model organism for flowering plants because it has a relatively small genome and a rapid life cycle. Last December, it was announced that Arabidopsis' genome had been completely sequenced, a first in plant genomics (see related article).

"Plants respond to a variety of directional signals such as light and gravity," said Liscum, who earned the 2000 New Investigator Award from the American Society of Photobiology for his work with Arabidopsis. "As seedlings, they identify the direction of gravity and grow away from it until they find light using their photoreceptors. When they find light, they grow toward it. Our goal is to determine all genes involved in this light-dependent response and how they function to benefit the plant."

Using mutational analyses, a process in which plants missing certain genes are compared, Liscum's research team has identified and cloned three genes involved in phototropism. The first gene encodes a blue light photoreceptor responsible for controlling phototropism in low light conditions. The second encodes a protein that interacts with this photoreceptor and might function to regulate the flow of the plant hormone, auxin. The third gene encodes a protein that regulates gene expression in response to changes in auxin levels induced by the activities of the first and second proteins.

"Working together, these proteins form a signaling pathway that allows plants to move in order to maximize capture of light in different colors and intensity," Liscum said.

In conjunction with the recent completion of the Arabidopsis genome sequencing project, the National Science Foundation announced the 2010 Project, which will provide up to $25 million to support research to determine the function of all genes in Arabidopsis by the year 2010. Liscum has submitted a proposal to the 2010 Project that has grown from his studies on phototropism.

The National Science Foundation and the U.S. Department of Agriculture provided grant funding for Liscum's Arabidopsis research.

A short video demonstrating how Arabidopsis seedlings respond to blue light is available online at www.biosci.missouri.edu/liscum/phototropism.html.

For more information, contact Jason L. Jenkins of the University of Missouri-Columbia at 573-882-6217 or JenkinsJL@missouri.edu.

Source: University of Missouri News Bureau

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