By Ishani Ganguli, Globe Correspondent | September 15, 2006
Scientists yesterday unveiled the first complete genetic sequence of a tree -- a poplar known as black cottonwood -- and are already using the draft to boost the species' usefulness and help scientists better understand the molecular basis of what makes trees unique.
Besides being a useful research model for plant scientists, the hardy, fast-growing black cottonwood and other poplars are also important sources of fiber for paper and lumber. A genetic ``roadmap" of how poplars form wood will help scientists harness this material to make liquid fuels such as ethanol, said coauthor Carl Douglas, professor of botany at the University of British Columbia. ``We need to know how [wood] is made to know how to use it."
Black cottonwood is the third plant to be sequenced, after the small flowering plant Arabidopsis thaliana and rice. When scientists compared the sequence to those of other plants, the tree showed an expanded repertoire of genes that help resist pests and disease, adapt to changing seasons, form thickened cell wall structures to make wood, and transport water and organic molecules.
The genetic mapping effort, by a consortium of researchers from 34 institutions around the world including the US Department of Energy, took four years and cost roughly $7 million to $10 million, researchers said.
Within five years, botanists will begin to apply their genetic insights to selectively breed poplars to grow faster, better resist pests, and take up less agricultural land, estimated Gerald Tuskan, lead author of the study that appears in today's issue of the journal Science. Within 15 years, Tuskan, a plant molecular ecologist at Tennessee's Oak Ridge National Laboratory, predicts such enhanced trees will grow readily on farms.
The trees also have great potential as a source of liquid fuel, Tuskan and others said at a telephone news conference yesterday. Grasses are now being experimentally used to create ethanol -- a gasoline substitute -- but trees would be more efficient sources of the fuel, he said, and the genome research will help scientists figure out how to better extract the fuel.
Despite its relatively small genome, the black cottonwood has genes for more than 45,000 potential proteins -- the largest number found in any genome to date. Researchers are working to figure out roles for the approximately 50 percent of encoded proteins that have no known function.
Tuskan and others are refining the poplar's draft sequence and leveraging these findings toward what Sam Foster of the US Forest Service called the ``next hurdle" -- sequencing the much larger genomes of pine and other trees.
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