July 1, 2010
Source: SciDev.Net
by Rhiannon Smith
An international consortium aiming to re-engineer rice to increase yields by 50 per cent is about to move into the second phase of its decades-long project.
The project aims to genetically modify rice to use a more efficient method of photosynthesis — the process by which plants convert carbon dioxide into carbohydrates needed for growth.
Rice has a type of photosynthesis called C3. But some plants, including maize and sorghum, have evolved to use a type called C4. The C4 crops are anatomically different from C3s and are better at concentrating carbon dioxide around a particular enzyme — RuBisCO — which is crucial in photosynthesis.
If the scientists are successful in creating rice that follows the C4 pathway the crop could produce 50 per cent more grain, and would require less water and fertiliser.
The C4 plants work best in hot climates, so could be important as global warming increases.
"As temperatures rise, C4 plants will photosynthesise better than C3s," said Richard Leegood, a plant biologist from the UK-based University of Sheffield, which is leading an international team of researchers, coordinated by the International Rice Research Institute (IRRI) in the Philippines.
The project received US$11.1 million of funding over three years from the Bill and Melinda Gates Foundation in October 2008.
Most of this money has gone to IRRI, said Leegood, where researchers are doing the mammoth task of screening plants to try to identify the genes that control photosynthesis.
The project is a long-term venture — Leegood says that it will be at least 20 years before the modified rice is available.
"Many genes need to be manipulated, then engineered traits need to be transferred into commercial varieties."
Since C3 photosynthesis evolved naturally into the C4 type in other plants more than 60 times through history, Leegood hopes that the public will accept this GM rice.
"It is not an unnatural process; it's something that plants do ordinarily."
Lewis Ziska, a plant physiologist at the US Department of Agriculture said: "This kind of innovative work is crucial if we are going to meet the demands of an expanding population"..
Although there are many other issues that cause food insecurity, Leegood said that this solution could tackle those limitations that are "inherent" in the production of such crops.
The Sheffield work forms part of its Project Sunshine, a programme that investigates how the power of the sun can be harnessed to meet the world's increasing food and energy needs.
Image: Flick/IRRI images
雄心勃勃的转基因稻米计划进入第二阶段
一个致力于重新改造水稻从而增加水稻产量50%的国际联合研究组织将要进入它的长达数十年的项目的第二阶段。
该项目的目标是对水稻进行转基因改造从而使用一种更加高效的光合作用方式。光合作用是植物把二氧化碳转换成生长所需的碳水化合物的过程。
水稻有一种称为C3的光合作用。但是一些植物，包括玉米和高粱，进化成了使用C4型的光合作用。C4作物在结构上不同于C3作物，而且能够更好地让二氧化碳在一种称为RuBisCO的酶的周围聚集。这种酶对于光合作用具有关键作用。
如果科学家成功地培育出了按照C4路径进行光合作用的水稻，这种作物的产量可能增加50%以上，而且需要更少的水和化肥。
C4植物在炎热气候的生长最好，因此随着全球变暖的增加，这可能很重要。
“随着气温的上升，C4植物将比C3植物的光合作用更好，”英国谢菲尔德大学的植物生物学家Richard Leegood说。他领导着一个由菲律宾的国际水稻研究所协调的国际研究团队。
该项目在2008年10月获得了比尔与美琳达•盖茨基金会的为期3年的1110万美元的资助。
Leegood说，这笔钱的大部分流入了IRRI。在那里，科学家正在进行筛选植物从而试图发现控制光合作用的基因的庞大任务。
这个项目是一个长期投资——Leegood说在这种经过修改的水稻出现之前至少需要20年时间。
“许多基因需要加以操纵，然后把需要转移到商业品种中的性状加以改造。
由于在历史上其他植物C3光合作用自然进化成C4类型超过60次，Leegood希望公众可以接受这种转基因水稻。
“这不是一个不自然的过程；这是植物常做的事情。”
美国农业部的一位植物生理学家说：“如果我们要满足不断增长的人口的需求，这种创新工作是至关重要的。”
Leegood说，尽管有许多其他导致粮食保障问题的原因，这种解决方案可以解决这类作物生产的“固有”限制。
Sheffield 大学的这项工作形成了它的Sunshine计划的一部分，这是一个研究如何利用太阳光从而满足全世界不断增长的粮食和能源需求的项目。
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