Corvallis, Oregon
July 23, 2003

Forestry researchers at Oregon State University have made an important breakthrough for the use of genetic engineering with trees, one of the few types of plants that have most resisted the advances being made elsewhere in the biotechnology revolution.

The new findings, just published in the July issue of the international journal Plant Physiology, applied a recently-developed method called "activation tagging" that will allow researchers for the first time to accurately "label" genes in trees, identify their function, induce new gene variations, and learn how the variants will be different.

The scientists have also used the technique to control growth and induce "semi-dwarfism" in trees. This advance, after refinement, may be of key importance to the nursery industry or for use in silviculture.

"This is a basic advance for the use of genetic engineering in forestry and horticulture that could find a number of applications," said Steven Strauss, a professor of forest science at OSU and one of the world's leading experts in this field. "This gives us for the first time a much better way to learn the function of various genes in trees and then consider how they might be used to improve tree characteristics for specific uses."

Many plants used in crop agriculture have had important new characteristics added via genetic engineering, Strauss said, creating such traits as faster growth, resistance to disease and seedless fruit. But for a variety of reasons such progress has been slow with trees - as plants, they take a very long time to grow and reproduce, their genomes are poorly understood, and they're difficult to inbreed.

Conventional cross-breeding of trees has been done for centuries, but it's a process that's slow and haphazard, he said. For one thing, some of the traits that may be desirable, such as reduced height, sterility, or altered chemical qualities to promote industrial or food nutrition, have little survival value in a natural environment. Genes that impart such traits are therefore rarely found in nature, and breeders have a tough time finding genes for these traits.

The new approach being used at OSU creates new mutations, instead of mapping natural mutations. Although natural mutations are abundant, it's hard to link the myriad of variants in nature to specific traits. By inserting an "enhancer," which is a piece of DNA that can control the expression of nearby genes, researchers can change the native expression pattern of genes and also know which genes have been affected.

The resulting new variants can then be grown and studied to determine their new characteristics, and used in future plants if the characteristic is desirable. "This approach actually mimics natural diversity, but in this case we've induced changes and tagged the new genes so we know exactly what has changed," Strauss said. "This allows a new kind of breeding."

Like traditional breeding, he said, it assembles and amplifies genetic diversity from within related species. However, unlike breeding, genetic engineering methods are used so that you can know with very high confidence what genes are causing the new characteristics you have induced.

"This may be a significant advance for use in horticulture or other intensively-grown tree crops," Strauss said. "It gives us an important new tool to work with." The OSU research has already found a way to control dwarfism in poplar trees, which might lead to shorter trees with fat trunks that produce more usable wood. Another possible use of dwarf trees, Strauss said, might be in the nursery industry.

"One thing that could be considered a desirable trait is a nursery tree that grew very quickly to a desired height, then dramatically slowed its growth," he said. "This would be very useful for some trees used in a home or urban setting, where people want their trees to grow quickly but then stop at some point and not get too much larger, so they don't threaten houses or power lines and are less costly to maintain."

Commercially available growth-promoting sprays could override the influence of a genetically-engineered dwarf characteristic to produce rapid growth in early years, Strauss said, and then the genetic characteristics of the dwarf variety would take over once application of growth regulators was stopped.

Semi-dwarf trees could also be developed for increased fiber and fruit production, greater ease of management and reduced risk of introduction into wild populations, the researchers said in their report.

Because shorter trees could not compete with wild trees, they would pose no threats to wild forests, he said. Tightly linking such genes to exotic genes for traits such as pest resistance, for which release into the wild could pose ecological concerns, would provide a strong barrier to their spread.

The new research was funded by the Tree Genetic Engineering Research Cooperative based at OSU, which focuses on biosafety and genomic studies of trees, and the Consortium for Plant Biotechnology Research.