2002년 Science 3월 1일자에 실린 Letter. 한번 사라진 종의 EcoNiche를 다시 채워 넣는 것이 가능할까? 최근 늑대와 반달곰의 복원을 실행중인 우리나라의 생태학자들이 한번쯤 읽어 보았으면 하는 바램이다. 비교적 안정된 생태계는 마구 쌓아올려진 블럭과 같다. 중간의 하나를 빼어 버리면 우르르 무너지고, 그것을 다시 채워넣는 것은 더더욱 어렵다. 복원하고자 하는 생태계는 다른 방법으로 그 블럭 없이 이미 안정되어 있기 때문이다. 마지막 단락은 생명공학자들과 생태학자들의 입장을 잘 표현하고 있다. --김우재
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BIOTECHNOLOGY: Can Genetic Engineering Help Restore 'Heritage' Trees?
Charles C. Mann and Mark L. Plummer*
BIOTECHNOLOGY: Can Genetic Engineering Help Restore 'Heritage' Trees?
Charles C. Mann and Mark L. Plummer*
In the summer of 1904 Hermann W. Merkel, a forester at the New York Zoological Park, noticed peculiar cankers on the stately chestnut trees that lined the zoo's pathways. The cankerscaused by the Asian fungus Cryphonectria parasiticasoon circled the trunks completely, killing the trees. Initially, Merkel's report was treated as a curiosity. But the fungus spread with astonishing speed. By the end of World War I, the American chestnut, which once dominated many eastern forests, was fast approaching oblivion.
Now, forest-biotech researchers believe genetic engineering might help restore this majestic species--and possibly other "heritage trees" menaced by disease, including elms, white pine, butternut, and several species of California oak. So promising are the new techniques that researchers from academia, industry, government, and private foundations are forming a coalition to bring back these species, starting with the American chestnut. If the effort pays off, it would put an end to decades of scientific frustration and, its backers hope, some of the negative aura of genetic engineering (see main text).
Since 1983 the American Chestnut Foundation has been trying to restore the species using conventional breeding. It has been crossing American chestnuts (Castanea dentata) with blight-resistant Chinese chestnuts (Castanea mollissima), then repeatedly "back-crossing" hybrids that showed resistance, to obtain resistant trees that look like pure American chestnuts. Under the best of circumstances, back-crossing takes decades, and the end product would still have many unwanted Asian genes. But the problem has proven even harder to solve than the foundation initially anticipated.
Blight resistance in the Chinese chestnut is largely due to three genes located on widely separated portions of the plant's genome. Because the genes are inherited independently, the only way to pass on the trait is to mate resistant hybrids with other resistant hybrids, and that entails creating many resistant hybrid lines--"really a difficult proposition," says William Powell of the State University of New York (SUNY) College of Environmental Science and Forestry in Syracuse.
To several researchers, including Powell and Charles Maynard of SUNY and Scott Merkle of the University of Georgia in Athens, genetic engineering offers a clear shortcut. But it, too, has proven tough. "The chestnut hates genetic manipulation," says Maynard. The tree is so difficult to propagate in culture, he jokes, that "it's as if it wants to go extinct." Indeed, scientists spent a decade devising a reliable method for propagating them in the field, a crucial first step.
The researchers are now looking for genes with antifungal properties. A leading candidate, say Powell and Maynard, is OXY, a wheat gene that encodes oxalate oxidase. Oxalate oxidase breaks down oxalic acid, the compound exuded by Cryphonectria parasitica to kill cells. By splicing in OXY, Powell and Maynard hope to endow chestnut cells with a weapon to fight back.
Powell, Maynard, and Merkle may soon get some much-needed help. Last November, a diverse group of academic, government, and private chestnut researchers* met at the North Carolina Biotechnology Center's Institute of Forest Biotechnology in Research Triangle Park to form a coalition to bring back the American chestnut and other heritage trees. According to institute head Edward Makowski, the parties are still working out the best legal structure for the group, which could license some patented genes from its corporate members. He hopes to resolve these issues "within the next 30 to 90 days."
But even if the coalition can design a resistant chestnut, the problem will not necessarily be solved, according to Roger Sedjo, an economist at Resources for the Future in Washington, D.C. The ecological niche formerly occupied by American chestnuts "was filled largely by oak trees," Sedjo notes. "Part of the question is, 'Could the American chestnut reestablish itself on a wide-scale basis?' Once it's been displaced, it might not get back in there" without major effort. Although he acknowledges these obstacles, Makowski notes that "the loss of the chestnut was an enormous ecological disaster. I can't imagine anything more exciting than the chance to reverse it."
Contributing correspondent Charles C. Mann and Mark L. Plummer of Washington state write regularly for Science.
Participants included the American Chestnut Foundation, the U.S. Forest Service, the American Lands Alliance, the forest-biotech firms Arborgen and Mendel Biotechnology, and academic researchers such as Maynard and Ronald Sederoff of North Carolina State University. |}}
Participants included the American Chestnut Foundation, the U.S. Forest Service, the American Lands Alliance, the forest-biotech firms Arborgen and Mendel Biotechnology, and academic researchers such as Maynard and Ronald Sederoff of North Carolina State University. |}}
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