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2-Plants: Transgenic trees hold promise for pulp and paperindustries

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TITLE:  Transgenic Trees Hold Promise for Pulp and Paper Industries
SOURCE: North Carolina State University, USA, Press Release
DATE:   Apr 1, 2003

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Transgenic Trees Hold Promise for Pulp and Paper Industries

The expensive, energy-intensive process of turning wood into paper costs
the pulp and paper industries more than $6 billion a year. Much of that
expense involves separating wood's cellulose from lignin, the glue that
binds a tree's fibers, by using an alkali solution and high temperatures
and pressures. Although the lignin so removed is reused as fuel, wood
with less lignin and more cellulose would save the industry millions of
dollars a year in processing and chemical costs. Research at North
Carolina State University shows promise of achieving that goal.

By genetically modifying aspen trees, Dr. Vincent L. Chiang, professor of
forest biotechnology, and his colleagues have reduced the trees' lignin
content by 45 to 50 percent - and accomplished the first successful dual-
gene alteration in forestry science. Their results are described in the
current issue of the Proceedings of the National Academy of Sciences
(PNAS). According to Chiang, the NC State research shows not only a
decrease in lignin but also an increase in cellulose in the transgenic
aspens. And their work demonstrates another benefit: the trees grow faster.

That is very good news for the wood, paper and pulp industries, which do
multibillion-dollar business worldwide. Fast-growing, low-lignin trees
offer both economic and environmental advantages, because separating
lignin from cellulose - using harsh alkaline chemicals and high heat - is
costly and environmentally unfriendly. Harvesting such trees, using them
as "crops" with desirable traits, would also reduce pressure on existing

Chiang and his team chose aspens because, he says, "they're the lab rats
of forestry research." The scientists scratch the leaves and expose the
wound to bacteria carrying the beneficial genes. Treated leaf-disks, with
their enhanced genomic structure, are then cloned, producing trees with
predictable qualities.

As with any research involving genetic engineering, Chiang's modified
aspens have faced questions of real-world properties, resistance to
insects and diseases, and the possibility of unforeseen ecological
impacts. "There is a need for more data concerning the environmental
effects and field performance of transgenic trees," said Chiang, "but
four-year field trials of such trees in France and the United Kingdom
show that lignin-modified transgenic trees do not have detrimental or
unusual ecological impacts in the areas tested."

In previous work, Chiang and his team had successfully reduced lignin in
aspens by inhibiting the influence of a gene called 4CL. The current
research modifies the expression of both 4CL and a second gene, CAld5H,
in the trees. This dual-gene engineering alters the lignin structure, and
produces the favorable characteristics of lower and more degradable
lignin, higher cellulose and accelerated maturation of the aspens' xylem

The research is described in the paper "Combinatorial modification of
multiple lignin traits in trees through multigene co-transformation,"
published online by PNAS on March 31.

Chiang is co-director of the Department of Forestry's Forest
Biotechnology Group in the College of Natural Resources at NC State.
Headed by Chiang and Dr. Ron Sederoff, Edwin F. Conger and Distinguished
University Professor of Forestry and a member of the National Academy of
Sciences, the group is one of the world's leading research organizations
studying the molecular genetics of forest trees. The Forest Biotechnology
Group is a key part of NC State's research strength in genomics, an
important new area of scientific research focused on identifying and
mapping all the genes of living organisms. Its work is leading to a
better understanding of the genetic basis of biological diversity,
improved disease resistance in important tree species, and increased
commercial forest productivity.

According to Dr. Bailian Li, associate professor of forestry at NC State,
Dr. Chiang's results in this aspen model species are "very significant"
and will have dramatic impacts on the future genetic improvement of
forest trees for pulp and paper production. "The improved tree growth and
high cellulose content will increase pulp-yield production, while the
reduced lignin content will reduce the pulping cost and energy
consumption in the pulping process," he said. "The ability to produce
high-yield plantations with these desirable characteristics will enable
us to produce wood more efficiently on less land, allowing natural
forests to be managed less intensively - for habitat conservation,
aesthetics and recreational uses."

Citing the Forestry Department's Industry-Cooperative Tree Improvement
Program - working to improve plantation productivity, adaptation and
disease-resistance in North Carolina's loblolly pines - Li said, "Results
from Dr. Chiang's research are very encouraging to our research. Although
his research is on aspen, the valuable information on genetic regulation
of wood formation should be useful for our efforts in producing pine
plantations with lower lignin, higher cellulose, and faster growth rates."

- mueller -

Note to editors: An abstract of the Proceedings of the National Academy
of Sciences paper follows.

"Combinatorial modification of multiple lignin traits in trees through
multigene co-transformation"

Authors: Laigeng Li (NC State); Yihua Zhou (Chinese Academy of Sciences,
Beijing); Xiaofei Cheng (the Noble Foundation); Jiayan Sun (NC State);
Jane M. Marita, John Ralph (University of Wisconsin); and Vincent L.
Chiang (NC State).

Date: Published in the March 31 early online edition of Proceedings of
the National Academy of Sciences

Abstract: Lignin quantity and reactivity (which is associated with its
syringyl:guaiacyl (S/G) constituent ratio) are two major barriers to
woodpulp production. To verify our contention that these traits are
regulated by distinct monolignol biosynthesis genes, encoding 4-
coumarate:coenzyme A ligase (4CL) and coniferaldehyde 5-hydroxylase
(CAld5H), we used Agrobacterium to co-transfer antisense 4CL and sense
CAld5H genes into aspen (Populus tremuloides). Trees expressing each one
and both of the transgenes were produced with high efficiency. Lignin
reduction by as much as 40% with 14% cellulose augmentation was achieved
in antisense 4CL plants; S/G increases as much as 3-fold were observed
without lignin quantity change in sense CAld5H plants. Consistent with
our contention, these effects were independent but additive, with plants
expressing both transgenes having up to 52% less lignin, 64% higher S/G
ratio and 30% more cellulose. S/G increase also accelerated cell
maturation in stem secondary xylem, pointing to a role for syringyl
lignin moieties in coordinating xylem secondary wall biosynthesis. The
results suggest that this multigene co-transfer system should be broadly
useful for plant genetic engineering and functional genomics.

Media Contacts:
Dr. Vincent L. Chiang, 919/513-0098
Paul K. Mueller, News Services, 919/515-3470