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By giving a Chinese
rice variety a second copy of one of its own genes, researchers have boosted
its yield by up to 40%. The change helps the plant absorb more fertilizer,
boosts photosynthesis, and accelerates flowering, all of which could contribute
to larger harvests, the group reports today (July 22, 2022) in Science.
The yield gain from a
single gene coordinating these multiple effects is “really impressive,” says
Matthew Paul, a plant geneticist at Rothamsted Research who was not involved in
the work. “I don’t think I’ve ever seen anything quite like that before.” The
approach could be tried in other crops, too, he adds; the new study reports
preliminary findings in wheat.
A crop’s yield is
fiendishly complex because many genes interact to influence plant productivity.
For years, biotechnologists have searched for single genes that augment yield,
without much luck. In recent years they’ve shifted their interest to genes that
control other genes, and therefore multiple aspects of physiology, such as
taking up nutrients from the soil, setting the pace of photosynthesis, and
directing resources from leaves to seeds. Modifying one such regulatory gene in
maize gives a 10% higher yield—a major gain compared
with the 1% increase per year achieved by traditional plant breeding.
To find other
candidate yield boosters, a team led by plant biologist Wenbin Zhou of the
Chinese Academy of Agricultural Sciences (CAAS) combed through 118 rice and
maize regulatory genes, which encode proteins called transcription factors,
that other researchers had previously identified as likely important in
photosynthesis. Zhou’s team sought to find out whether any of the genes were
activated in rice grown in low-nitrogen soil, because such genes might boost
uptake of the nutrient. Increasing their activity in rice grown in regular soil
could nudge the plant to draw in even more nitrogen—and make more grain.
The team found 13
genes that turned on when rice plants were grown in nitrogen-poor soil; five
led to a fourfold or greater boost in nitrogen uptake. They inserted an extra
copy of one of the genes, known as OsDREB1C, into a rice variety
called Nipponbare that’s used for research. They also knocked out the gene in
other individual rice plants. Greenhouse experiments by Shaobo Wei and Xia Li
of CAAS showed plants without the gene grew less well than control plants,
whereas those with extra copies of OsDREB1C grew faster as
seedlings and had longer roots.
Good nutrition was one
reason: Isotopic tracers revealed the plants with extra copies of OsDREB1C took
up extra nitrogen through their roots and moved more of it to the shoots. The
modified plants were also better equipped for photosynthesis; they had about
one-third more chloroplasts, the photosynthetic organelles within plant cells,
in their leaves and roughly 38% more RuBisCO, a key enzyme in photosynthesis.
Planted in the field over 2 to 3 years, the enhanced rice gave higher yields at
three sites in China with climates ranging from temperate to tropical.
Importantly, the
researchers also transformed a high-yielding rice variety often planted by
farmers by adding an extra copy of the gene. These modified modern rice
plants produced up to 40% more grain per plot than
did controls, the researchers report. “That’s a big number,” says Pam Ronald, a
rice geneticist at the University of California, Davis. “Amazing.”
As in the greenhouse
experiments, the modified plants in the field boasted both bigger grains and
more of them. “What they’ve done is to take a very good [rice variety] and
shown they can make it better,” says Steve Long, a plant physiologist at the
University of Illinois, Urbana-Champaign, who adds that the result is a “lot
more convincing” than improving a research variety.
The modified plants
also flowered sooner, which gave them more time to devote to making grain.
Faster flowering can offer other advantages, depending on the environment, for
example allowing farmers to grow more crops per season or to harvest crops
before damaging summer heat sets in. However, although the modified Nipponbare
flowered up to 19 days earlier, the widely farmed variety of rice bloomed just
2 days earlier.
To demonstrate broader
potential, the team added the rice OsDREB1C gene to a research
variety of wheat and found the same types of effects. OsDREB1C and
similar genes are present not just in rice, wheat, and other grasses, but also
in broad-leaved plants. The researchers discovered comparable outcomes from
adding an extra copy to the well-studied mustard plant called Arabidopsis.
That’s consistent with a common role across the plant kingdom, suggesting other
kinds of crops might be amenable to yield boosts from this modification.
Transgenic crops such
as the rice Zhou’s team made are unacceptable to some consumers. But Zhou and
colleagues say the same yield boost could be accomplished by editing the
plant’s own genes, which in some countries is now more lightly regulated than
transgenic engineering. Another benefit is that increasing nitrogen efficiency
of crops could lessen pollution of streams and lakes from excess fertilizer
that runs off fields, Ronald says. And improved photosynthesis will be vital for adding to global food supplies,
notes Steven Kelly of the University of Oxford in a commentary. “You can get
huge jumps if you’ve got the right transcription factor,” Long says. “I’m sure
there’ll be more.”
|Source: Online/KSU
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