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     Sep 10, 2011

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.

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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