Genetic Engineers Decaffeinate Coffee

Coffee plants that produce much reduced levels of caffeine have been created by genetic engineers.

Researchers in Japan used a technique called RNA interference to silence a key gene for making caffeine in coffee plants. This technique cut caffeine in young coffee plants by up to 70 per cent.

The demand for decaffeinated coffee is growing globally because of the possible adverse health effects of caffeinated coffee. Caffeine can trigger palpitations and increase blood pressure in sensitive individuals.

The team says consumers will not be put off by the idea of genetically modified coffee as it is actually a good GM organism for health. The other key advantages of GM decaffeinated coffee, says the researchers, are that it should be cheaper and retain all the taste of regular coffee. The expensive processes currently used to extract caffeine from normal beans also strip other flavour compounds from the coffee.

Caffeine is produced in coffee plant cells from a natural plant chemical in three steps. Each step involves a chemical process called methylation. The team has now managed to silence the second gene involved in this process so that caffeine cannot be produced.

Modified one-year old seedlings showed a reduction in caffeine content of 50 to 70 per cent in their leaves. It will be at least four years before these GM plants blossom and therefore produce beans. Previous attempts to genetically alter the caffeine content of coffee plants have involved a less efficient technique than RNA interference.

Category:        Science & Technology
Source:           Adapted from: New Scientist, June 18, 2003
Words:           250

遗传工程学家去除咖啡中的咖啡因

遗传工程学家已经培育出咖啡因含量大为减少的咖啡树。

日本的研究人员使用一种被称为“核糖核酸干涉“（RNA interference）的技术来抑制一种在咖啡苗树制造咖啡因的重要基因的生长。这种技术能使咖啡幼苗里咖啡因含量减少高达百分之七十。

由于咖啡含有咖啡因，可能对健康产生不利影响，所以全球对脱因咖啡的需求正在增加。咖啡因会在敏感人群中引发心悸，并使之血压上升。

该组研究人员指出，消费者不会由于基因改良咖啡这个概念而产生反感，因为它实际上是个有益健康的基因改良生物。研究人员说，基因改良脱因咖啡的其他主要优点是，它应该更便宜，并保留普通咖啡的所有品味。目前所采用的从普通咖啡豆里提取咖啡因的过程比较昂贵，同时也除去了咖啡含有的其它品味成分。

咖啡因是由一种天然植物化学成分在植物细胞里分三个阶段制造出来的。每个阶段都涉及一种称为甲基化作用的化学过程。现在该组研究人员已经成功地抑制住涉及此过程的第二种基因的生长，因此咖啡因不能产生出来。

经过改良后生长了一年的咖啡幼苗显示出叶子里咖啡因含量减少了百分之五十至七十。这些基因改良幼苗至少需要四年才能开花结豆。从效果上看，以往采用的从基因上改变咖啡苗咖啡因含量的技术比不上“核糖核酸干涉“方法。