In two studies reported in the journals Nature and Science this year, Chory and colleagues diagrammed how brassinosteroids trigger a cascade of biochemical events that ultimately activate the expression of diverse genes involved in plant development, from cell-wall metabolism to reproductive organs. “We are now in a position to modify steroid levels or the signaling pathway to either miniaturize or grow the plant bigger,” says Chory. The Nature study, in particular, generated significant media coverage, with the vision of grass that never needs mowing. Even more importantly, Chory adds, these findings could improve plant yield for agriculture worldwide.

In an earlier study, Chory and colleagues identified a gene that controls flowering when “shade avoidance” is triggered. Shade avoidance syndrome is a novel molecular mechanism activated when sun-loving plants, such as Arabidopsis, get stuck in the shade. Short on sunlight, the plant taps this pathway to elongate its stem, restrict leaf and root development, and—if all else fails—produce what Chory calls a “desperation flower” that allows the shade-stressed plant to set seeds and ensure survival of at least some offspring.

“All our studies—on brassinosteroids, auxin [another hormone that controls plant development], and the quality and quantity of light—suggest how plants grow in different environments,” says Chory. “In the next five years, we want to understand how these different systems interact.” During that time, she notes, basic research on plants will contribute to biofuels and to the creation of hardier, higher-yielding crop varieties with added nutritional content. “In fact, the study of plant genomes might contribute more to human health and well-being than the study of any animal genome.”

		Even as biologists released the Arabidopsis thaliana genome sequence in 2000 they were launching another ambitious endeavor: Arabidopsis 2010, a project to map and explain by the year 2010 the function of each of the mustard plant’s roughly 25,000 genes. Their goal is to outline nothing less than the complete workings of a flowering plant. “The Arabidopsis genome is small enough that we can understand every gene,” says HHMI investigator Joanne Chory, a plant biologist at the Salk Institute and a principal author of the project’s planning document. Ultimately, Arabidopsis 2010’s goal is to build a body of knowledge—a kind of modern encyclopedia, with interactive tools—that plant biologists can tap as a central reference. Through 2005, Arabidopsis 2010 had funded 86 individual projects, primarily with support from the National Science Foundation. Participants, including HHMI investigators Steve Jacobsen, David Bartel, and Daphne Preuss, are building a toolkit of sorts, including valuable seed banks of modified Arabidopsis lines such as “knock-outs,” which lack a given gene. Other projects range from cell wall studies to microarray experiments that test gene function. Biologists have already begun talk of Arabidopsis 2020, a program to build on this basic toolkit, with projects that not only extend basic research but may also serve practical applications in agriculture, environmental science, and other fields. For more information, see the “Mid-Course Assessment of the Arabidopsis 2010 Project”. —K.B.

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