May 30, 2000 / San Jose Mercury News / Lisa M. Krieger
"No tree lover will ever forget his first meeting with the sugar pine ... sun tree of the Sierra. This is the noblest of pines yet discovered, surpassing all others not merely in size but in kingly beauty and majesty ... they are the priests of pines and seem ever to be addressing the surrounding forest." -- John Muir
According to this story, the reality, increasingly, is a tree that Muir might not recognize, an arboreal skeleton felled by a fungus called "white blister rust." But hope is on the horizon, thanks to strategies borrowed from the human genetic revolution. By decoding the genetic operating instructions of plants, scientists are striving to heal sick trees, and protect and perhaps improve healthy ones. The emerging field of plant genomics could restore to forests the grandeur of sugar pines, elms and chestnut trees devastated by disease. It could also create vast forests of uniformity, filled with mass-produced eucalyptus or pine for timber, paper and other commercial purposes.
Molecular geneticist David Neale, director of the Institute of Forest Genetics at the University of California-Davis, was quoted as saying, "This is restoration ecology, using techniques straight out of the Human Genome Project. If we learn to produce more, on less, we can leave the native forests alone. Many of the approaches developed by the genomics industry, funded by the multimillion-dollar medical research infrastructure, have (forestry) applications."
The story says it remains true that only God can make a tree, as poet Joyce Kilmer wrote in 1913. Humans, however, are learning to tinker with nature's creation -- inducing genetic modifications that have the potential to change the world's landscapes, scientists reported at a recent symposium of "Bio 2000," an international biotechnology meeting in Boston. Research in tree improvement is mainly targeted at: reducing losses from disease and insect predation, such as blister rust or Dutch elm disease. Speeding tree growth rate, increasing the yield of commercial forests. Easing paper production by genetically manipulating lignin, the tough cellular material that gives trees the strength to withstand wind. The goal is to reduce lignin levels or make it easier to extract from trees.
Ron R. Sederoff, a professor in the department of forestry at North Carolina State University-Raleigh was quoted as saying, "Trees are in the earliest stages of domestication. We are 5,000 or 10,000 generations of natural selection behind agricultural crops like wheat or maize. By applying gene-based technologies, we believe major improvements are possible. We can improve conservation and restoration of endangered tree species ... and we can figure out how to grow trees in plantations more efficiently, so we can leave the natural forests alone." While agriculture has jumped onto the biotech bandwagon, creating many genetically altered food crops, forestry has, the story says, remained decidedly low-tech. The forestry genome research community has been small, poorly funded and not organized around a single species. Time-honored tree-breeding techniques -- choosing a seed, planting it, then watching it grow to see if the adult plant has the desired trait -- work fine if you're not in a hurry. The generation time of a tree can be as long as the working lifetime of the average scientist. And the traits of seeds are variable, so it is not clear, until they mature, exactly what traits they possess. The 25,000 to 50,000 genes that program plants -- controlling their shape, size, maturation, branching, flowering and wood characteristics -- until recently have remained hidden. The federal government, recognizing the enormous potential of plant genomics, launched a National Plant Genome Initiative in 1997. Private companies such as Monsanto and Weyerhauser have also climbed on board. Since then, thousands of plant genes have been identified. In December, researchers made scientific history by decoding a large part of the DNA of a plant, a weed called "Arabidopsis thaliana," affording the first glimpse of the genetic machinery of the plant world. Scientists have since begun exploring the genetic secrets of trees, ranging from the slender poplar to the towering sequoia.
Robert B. Goldberg, a University of California-Los Angeles professor of biology, was quoted as saying, "The emerging field of plant genomics offers great promise to identify all of the genes necessary to program the entire life cycle of major plants and to harvest these genes to make 'super plants' of the 21st century."
The story says that forest biotechnology tends to fall into two categories: simple cloning or more sophisticated genetic engineering, using gene mapping and manipulation.
Clonal propagation techniques do something nature alone cannot: replicate a perfect tree many times over. While seeds use half the DNA of each parent, cloning permits the mass production of offspring that are genetically identical to one parent tree. Gardeners and farmers have cloned plants for millenniums using vegetative cuttings. But new methods of tree propagation, which involve an embryo cloning technique known somatic embryogenesis, enables foresters to produce thousands of identical embryos from a single seed. Moreover, embryos produced at different times can be dried and stored and then germinated all at once in the spring to provide cloned plants of uniform size. Selected genes potentially could be introduced into the cloned embryos, resulting in trees resistant to disease and pests. Through cloning, scientists have immortalized the last surviving Liberty Tree at St. John's College in Annapolis, Md. The 400-year-old specimen was one of 13 such trees in each of the colonies where the Sons of Liberty plotted the American Revolution. Cloning three rare frost-tolerant specimens of California's coastal redwood has enabled the export of more than 1,000 hardy sequoias to frosty Germany. Cloning is also helping preserve Britain's black poplar, a water-loving tree that was a favorite subject for the landscape artist John Constable. It is now so rare that scientists know the exact location of each of the 7,000-odd specimens. So scientists are gathering cuttings from the tree, storing them in a "clone bank" of genetic information and generating offspring. The 1,000-year-old Sidney oak from England's historic Penshurst Place is also being cloned. Under cover of security guards and closed-circuit TV cameras, scientists recently took bark from the ancient giant and grafted it onto seedlings. The ultimate goal is to transfer the genes of this hardy tree to the region's less-vigorous oak newcomers.
More and more the story says, domesticated trees are beginning life as clones, often frozen until they are needed and then cultivated in vast hydroponic vats. The other approach -- mapping and manipulating the DNA in the chromosomes of those cells -- is more daunting. The goal of mapping is to correlate a particular trait -- for example, growth rate or wood density -- with particular DNA sequences. Knowledge of the number and individual effects of genes controlling complex traits will offer a better understanding of the genetic architecture of trees. Maps could aid tree breeding by identifying desirable traits out of the huge range of natural variation in the population. In this way, they lay the foundation for targeted breeding strategies in forest trees. Genetic maps are already being used at UC-Davis to chart which regions of a gene control traits of practical value such as wood quality, growth and disease resistance.
Eventually, they could reveal more subtle traits.
The story goes on to say that gene mapping is being used, as well, to locate the protective gene that enables a few lucky elms to respond quickly and efficiently to invaders, walling off invading fungus before it spreads.
Three genetically modified English elms -- nicknamed Tom, Dick and Harry -- have been created by Kevan Gartland of the University of Abertay, in Dundee, Scotland. The hope is that these trees, to be grown in containment facilities, will be protected by the introduced genes.
Gartland was quoted as saying, "To modify elms to restore to rightful position in habitat, we've begun to look at anti-fungal protein genes and how to modify internal architecture of elms."
(posted without permission)
