Gene code promises crops for all seasons
By Raja Murthy
MUMBAI - A Chinese research team working with a United States university has
found that the biology clock of plants, known as the circadian rhythm, can be
tweaked by altering a specific gene. The finding raises the prospect of
year-round harvests that make global food shortages a thing of the past.
"Farmers are limited by the seasons, but by understanding the circadian rhythm
of plants, which controls basic functions such as photosynthesis [by which
plants process sunlight into food, with release of oxygen] and flowering, we
might be able to engineer plants that can grow in different seasons and places
than is currently possible," Xing Wang Deng, a developmental biology professor
at Yale University told Science Daily on September 3. [1]
Deng co-authored the research paper on plants' circadian clocks that revealed
the findings, which appeared in the September 2
issue of the journal Molecular Cell. He runs the Deng Lab in Yale, and is also
director of the Peking-Yale Joint Research Center for Plant Genetics and
Agrobiotechnology, based in Beijing, China. Deng's expertise includes studying
the genetics behind the growth of rice and maize.
The China-US project was set up in 2001 to apply new biological research to
crop improvement, "an area of great interest and importance both to China and
to the United States", according to the Peking University-Yale team's website -
with fringe benefits for the rest of the world. The research effort involves
student exchanges between Yale and Peking University.
Deng's team studied botanical aspects of the circadian rhythm, which is the
inner timekeeper of almost all living beings, enabling biological processes to
synchronize with day and night . The word "circadian" comes from Latin "circa",
meaning "about" and "dies" or "day". In the botanical world, scientists say,
this inner alarm clock sets plant growth to start and stop depending on the
time of day and the four seasons.
Two leading biotechnology scientists, one of them world renowned, told Asia
Times Online that there were no dangerous implications of Deng's theory being
put into practice.
Altering the internal bio-clock of plants to make crops produce off season
could also have implications for evolving research on the human body clock,
which governs our circadian rhythm - tells us when to wake up and when to
sleep.
A landmark July 2006 study published in the journal for Proceedings of the US
National Academy of Sciences found that that the key to developing treatments
for problems like depression and insomnia disorders influenced by the circadian
rhythm would be predicting how the body's internal clock can be controlled.
Until that study, convention science had accepted that the working and sleep
patterns of mammals such as humans are regulated by the concentration levels of
a protein known as PER in the body. Pharmaceutical companies had long learned
how to manipulate PER levels in the body to treat disorders caused by
disruptions to the circadian rhythm.
More PER was believed to speed up a mammal's internal clock, causing it to feel
the need for more sleep. But the 2006 study found the opposite happens in an
animal's body clock. It is not an oversupply of PER that leads to shorter days
in affected animals, but insufficient PER.
Deng and his research team focused on the plant body clock to see how it can be
made to grow "off duty", in hours when it normally would not be possible for
growth genes to work. A plant's clock ticks through a link between using
"morning" and "evening" genes, with proteins related to the morning genes
stopping the evening genes at dawn - signaling the end of the night shift. By
sunset, these daytime proteins levels go to sleep and evening genes in plants
come out to work in a 24-hour cycle.
Deng's work breaks into daring new ground, given that scientists say the human
body clock itself dates back millions of years. Trying to figure out the
24-hour sleep and wake cycles of living beings, including plants, is something
that Deng and other scientists say is of great significance. Each cell in a
living being has its body clock to know when to work, or call it a day.
The focus of the team's research - which they hope will become a major
development in increasing the world's food supply - was a humble weed called
Arabidopsis, often found growing by car parks and railway tracks.
The Peking University-Yale team studied a Arabidopsis species of plants that
grows naturally worldwide in temperate climates, including Asia, particularly
Japan, eastern Africa, Europe, North America and Australia.
The Arabidopsis, belonging to the Brassicaceae or mustard family, has no
inherent economic value, but offers rare advantages for quick genetic and
molecular analysis. Deng's researchers used the Arabidopsis to study a key gene
in plant growth called the COP10-DET1-DDB1 (CDD) complex.
Their study showed DET1 as a core factor in the influencing the gene related to
the biological clock. This protein gene complex plays a crucial role in growth
of plants, animals and humans, but how it goes about doing so was not quite
clear, until Deng's team got involved.
Plants making less DET1 have a faster internal clock and take less time to
flower, according to co-author On Sun Lau, a former Yale graduate now at
Stanford University.
Sun Lau says that increasing knowledge of the components and roles of the
plant's circadian clock will help to choose or generate more fruitful traits in
crop and plants.
The circadian clock of plants now holds promise to reverse the world's Hunger
Clock, a World Bank estimate of the number of undernourished people in the
world, based on the count from the United Nations Food and Agriculture
Organization. The Hunger Clock stood at 947 million at the time of press,
underlining how significant for global agriculture the Chinese-American team's
findings could become.
Note
1. On Sun Lau, Xi Huang, Jean-Benoit Charron, Jae-Hoon Lee, Gang Li, Xing Wang
Deng. Interaction of Arabidopsis DET1 with CCA1 and LHY in Mediating
Transcriptional Repression in the Plant Circadian Clock. Molecular Cell; Yale
University. 3 Sept, 2011
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