Davis, California
November 27, 2007
Genetically engineered crop plants
that survive droughts and can grow with 70 percent less
irrigation water have been developed by an international team
led by researchers at the
University of California, Davis. The discovery offers hope
for global agriculture that is already grappling with limited
and variable water supplies.
Research findings concerning the new drought-tolerant plants
will be reported in the Nov. 26 online issue of the
Proceedings of the National
Academy of Sciences. In this study, tobacco plants were used
as a research model.
The University of California has filed a patent application on
this technology. The patent application is pending in the United
States and in a number of foreign countries. The patent rights
are covered by an exclusive arrangement between the University
of California and Arcadia
Biosciences, which has completed initial outdoor field
trials with the drought-tolerance gene in tobacco.
"This is an exciting development because it opens the door, not
only to producing plants that can survive periodic droughts, but
also to reducing the amount of irrigation water routinely used
to grow some of the world's most important food and fiber
crops," said Eduardo Blumwald, a professor and Will W. Lester
Endowed Chair in the Department of Plant Sciences.
Blumwald and UC Davis postdoctoral fellow Rosa Rivero
collaborated on the work with researchers at RIKEN Plant Science
Center in Japan; Biology Department Technion in Haifa, Israel;
the University of Nevada, Reno; and Hebrew University of
Jerusalem.
Drought and global agriculture
Droughts -- prolonged and abnormal shortages of water usually
caused by lack of rainfall -- have been a fact of life
throughout the ages. But scientists monitoring global climate
change warn that warming trends will likely result in more
frequent and widespread droughts, with serious implications for
agriculture and worldwide food security.
The National Center for Atmospheric Research has reported that
the percentage of the Earth's land area impacted by serious
drought has more than doubled during the past three decades.
"Because climate change is altering rainfall patterns," Blumwald
said, "agriculture must adapt by using strategies that range
from changing traditional farming practices to developing
genetically modified crops that can better tolerate drought and
make more efficient use of irrigation water."
Plants' response to drought
Plants have developed their own biological strategies for coping
with water shortages. In dry regions, annual plants avoid
seasonal drought conditions by having relatively short life
cycles and growing quickly during the wet season.
Furthermore, when water is scarce, plants are able to increase
their chances of survival by minimizing water loss through their
leaves, increasing root growth while reducing leaf growth, and
dropping their older leaves.
Blumwald and colleagues decided to investigate whether it might
be possible to enhance the plant's tolerance to drought by
delaying the shedding of leaves triggered by water shortage.
They conjectured that the loss of leaves was the result of
programmed cell death, a process by which the plant triggers
certain genes to initiate destruction of certain cells -- in
this case, leaf cells.
Genetically introducing drought tolerance in tobacco
The researchers set out to suppress the programmed death of leaf
cells and equip the plants to survive severe drought conditions.
Tobacco was chosen as an experimental plant because it is big,
fast growing and a good model for many other crop plants. The
researchers inserted into the tobacco plants a gene that
interrupted the biochemical chain of events that normally leads
to the loss of the plant's leaves during drought.
The genetically modified tobacco plants, and the non-modified
plants in the experiment's control group, were all grown in a
greenhouse under the same optimal conditions for 40 days. Water
was then withheld from all of the plants for 15 days, simulating
extreme drought conditions.
During the dry period, the non-modified tobacco plants in the
control group wilted, lost their green pigment and progressively
deteriorated. The genetically modified plants, however, remained
green and did not display signs of severe deterioration.
At the end of the 15-day induced drought, all of the plants were
re-watered for one week. The plants in the control group all
died, but the genetically modified plants recovered and resumed
normal growth, with little reduction in seed yield.
"Surprisingly, although the genetically modified tobacco plants
went more than two weeks without being watered, they maintained
relatively high water content and continued their photosynthetic
activity throughout the dry period," said researcher Rosa
Rivera.
"In short, with only minimal reduction in yield, these plants
survived on just 30 percent of the normal irrigation water --
severe drought conditions that killed all of the plants in the
control group," she said.
The research team is hopeful that similar results will be found
in crop plants such as tomatoes, rice, wheat, canola and cotton.
Upon completion of greenhouse experiments, the researchers plan
to carry the research forward into field trials.
Funding for this research was provided by the University of
California's Will W. Lester Endowment and Arcadia Biosciences
Inc.
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