Solving the Poplar Genome Puzzle
Wood from a common tree may one day play a major role in filling American gas tanks, according to scientists whose research on the fast-growing poplar tree was featured in a recent edition of Science.
The article, coauthored in part by three faculty members in Michigan Tech's School of Forest Resources and Environmental Science, highlights the analysis of the first complete DNA sequence of a tree, the black cottonwood, or Populus trichocarpa. It lays groundwork for the potential development of trees that could serve as the ideal feedstock for a new generation of biofuels such as cellulosic ethanol.
The research is the result of a four-year effort, led by the US Department of Energy's Joint Genome Institute and Oak Ridge National Laboratory, uniting the efforts of thirty-four institutions from around the world, including Michigan Tech.
The effort has been a mountaintop experience for the Tech team. "We have a long track record in Populus molecular genetics, and we've made a number of groundbreaking discoveries," said Professor Chung-Jui Tsai, director of the Biotechnology Research Center. "But this is a real milestone for the entire forest research community." She is working with Assistant Professor Victor Busov and Associate Professor Chandrashekhar Joshi in sequencing the poplar genome.
The research might solve some of the earth's most pressing ecological problems. "By understanding the tree genome, we could develop trees that lower greenhouse gases," said Joshi.
As evidence of global warming mounts, scientists are studying trees as an alternative energy source. Like fossil fuels, they release the greenhouse gas carbon dioxide when they burn. However, unlike oil and gas, they absorb it from the atmosphere as they grow, essentially mopping up after themselves through a process known as carbon sequestration.
"This opens up opportunities for environmentalists and biotechnologists to work together," Busov said. "Eventually, we might be able to use that knowledge to reduce greenhouse gases and improve soil fertility, as well as provide an enhanced source of biofuels."
Poplar's rapid growth and its relatively compact genome size of 480 million nucleotide units are among the many features that led researchers to target poplar as a model for biofuel production.
"Under optimal conditions, poplars can add a dozen feet of growth each year and reach maturity in as few as four years," said Sam Foster of the US Forest Service.
Poplar is the most complex genome to be sequenced and assembled by a single public sequencing facility and only the third plant to date to have its genome completely sequenced and published. The first, back in 2000, was the tiny weed Arabidopsis thaliana, an important model for plant genetics. Rice was the second, three years ago.
The poplar project supports a broader DOE drive to accelerate research into biofuels. Scientists envision a future where vast poplar farms in regions such as the Upper Midwest, the Pacific Northwest, and portions of the southeastern US could supply bio-refineries with the raw materials needed to manufacture fuels such as ethanol.
Now that the genes have been identified, the consortium of scientists is working on the next phase of the project: deciphering the role played by each gene.
"There are secrets to life embedded in this genome that we don't know anything about," Busov said. For instance, trees live longer and grow larger than any other living thing, and the mechanisms controlling that are encoded in their DNA.
"Our next step is to create knowledge from this information," said Joshi. "And the final step will be to use that knowledge with wisdom, to benefit every organism on earth."