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THE International Rice Research Institute (IRRI) in Los Baños,
Laguna announced a path-breaking research project that aims to
develop—invent is more apt—a rice variety that needs less water
and fertilizer but yields 50-percent more grain than the best
present-day varieties.
In the face of growing popu-lations, food
shortages and temperatures that could exceed 3.7°C above the 20th
century average by the end of the century, this scientific venture
is by any metric of primary importance.
The Bill and Melinda Gates Foundation gave the
C4 Rice Consortium $11 million to begin the project.
It will take three years to prove the concept
and 15 years to have a “functioning C4 rice” to quote Achin
Dobermann, the deputy director general for research of IRRI.
Can the gene of the rice plant that controls its
photosynthetic engine be tweaked so that it expresses itself with 4
carbon atoms rather than its normal 3 carbon atoms and still retain
its essential characteristics as a plant species?
Photosynthesis, as you might recall, is the way
plants produce carbohydrates from carbon dioxide and a hydrogen
source. The energy for the process comes from sunlight that’s
absorbed by chlorophyll that’s in the chlo-roplast. Water is the
hydrogen source and oxygen is released as a byproduct.
Photosynthesis consists of two sets of reactions. One set requires
light to produce energy-storing and reducing compounds. The other
uses these compounds to add hydrogen atoms to carbon dioxide to make
carbohydrates. These reactions can be summarized as 6CO2 + 6 H2O ?
C6H12O6+6O2.
We still do not understand the mechanism
responsible for water splitting in photosynthesis. Scientists
predict that within a decade, with the help of high-resolution
structures of photo-systems and biophysics, the electron transfer
reactions can be measured and perhaps understood (Falkowski and
Isosaki, Science, Oct. 24, 2008). Safety questions will also have to
be answered. Changing the water and nitrogen needs of a plant alters
its metabolism in a fundamental way. The potential for unintended
side effects is great.
The aim of the consortium is to make the 3-atom
rice behave photosynthetically like the 4-atom corn so that it can
convert light into energy more efficiently and, like corn, use less
water.
The first step is to try to understand the
genetics of C4 photosynthesis then locate these genetic controls in
rice or in another species close to or related to rice.
Dr. Dobermann admits that this “has not been
attempted before, but we are optimistic that it will succeed because
a lot of new knowledge has been gained in recent years.”
The head of the IRRI team of the consortium is
John Sheehy, a British physicist. If they can understand how the
gene that controls C4 photosynthesis functions they may be able to
device a way to transfer it to rice.
“We have to begin to understand,” Sheehy
said, “what effect a more efficient photosynthetic engine might
have on the overall performance of the rice plant, e.g., rate of
growth and size of the plant.
“The result of this strategic research has the
potential to benefit billions of poor people.”
The C4 Rice Consortium includes molecular
biologists, plant geneticists, plant physiologists, biochemists,
physicists and mathematicians. Its institutional partners are
specialized organizations in countries all over the world.
Our own Philippine Rice Research Institute in Muñoz,
Nueva Ecija, should follow the work of the IRRI team closely to
learn from it.
opinion@manilatimes.net
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