A silence that speaks volumes
A silence that speaks volumes
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DOI：
10.1038/35009245
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发表时间：
2000-04-20
期刊：
影响因子：
64.8
通讯作者：
Gura, T
中科院分区：
文献类型：
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作者：
Gura, T
© 2000 Macmillan Magazines Ltd生产花青素色素。研究人员将该基因连接到一个强大的启动子序列上，并将这种基因构建体转移到他们的矮牵牛中。然而，许多花不是深紫色的，而是杂色的，或者是纯白色的。“我们认为我们一定是把这个结构弄错了，”现在在图森亚利桑那大学的乔根森回忆说。经过仔细观察，研究人员发现，加速的查耳酮合酶基因不知何故使其自身和正常的矮牵牛基因都沉默了。乔根森创造了“共同抑制”这个词来描述这种自相矛盾的现象。当他进一步研究这一过程时，他注意到白色可以传给下一代。不过，也有部分花朵，恢复了紫色。这使他假设共抑制是由一种核酸介导的，可能是RNA，它没有在矮牵牛基因组中永久居住。大多数研究人员将这一发现视为矮牵牛的怪癖，直到两个研究小组在研究植物RNA病毒时开始获得类似的结果。在诺里奇，Baulcombe的团队正在烟草植物中表达马铃薯X病毒的基因。研究人员希望这些基因产生的病毒蛋白能够刺激烟草植物的防御，使植物能够抵抗病毒本身随后的攻击。在许多情况下，这是有效的，但是，与植物免疫的流行理论相反，引入的基因不需要翻译成蛋白质来赋予抗性。事实上，具有最强抗性的植物是那些导入基因沉默的植物。鲍尔科姆最终得出结论，引入的基因同时抑制了自身和病毒中的同一基因。位于科瓦利斯的俄勒冈州州立大学的John Lindbo、William Doughnard和他们的同事研究了烟草蚀纹病毒，获得了类似的结果。两个研究小组都开始怀疑共抑制是为了保护植物免受病毒攻击而进化的。当Baulcombe的研究小组和另外两个研究小组独立地证明几种植物病毒产生抑制共抑制的蛋白质时，这种情况得到了加强4 -6。这表明宿主和病原体之间存在一场经典的进化军备竞赛。
© 2000 Macmillan Magazines Ltd in production of the anthocyanin pigments. The researchers hooked up the gene to a powerful promoter sequence and ferried this genetic construct into their petunias. However, instead of deep purple, many of the flowers grew up variegated, or virgin white1.“We thought we must have made the construct wrong,” recalls Jorgensen, now at the University of Arizona in Tucson. On closer inspection, the researchers found that the revved-up chalcone synthase gene had somehow muted both itself and the normal petunia gene. Jorgensen coined the phrase ‘co-suppression’to describe this paradoxical phenomenon. As he studied the process further, he noted that the white colour could be passed on to the next generation. However, some of the flowers partially reverted back to purple. This led him to suppose that co-suppression is mediated by a nucleic acid, presumably RNA, that had not taken up permanent residence in the petunia genome. Most researchers dismissed the finding as a quirk of petunias, until two groups started to obtain similar results while working on plant RNA viruses. In Norwich, Baulcombe’s team was expressing genes from the potato virus X in tobacco plants. The researchers hoped that viral proteins produced by the genes would stimulate the tobacco plants’ defences, allowing the plants to resist subsequent attack by the virus itself. In many cases, this worked—but, contrary to prevailing theories of plant immunity, the introduced genes did not need to be translated into proteins to confer resistance. Indeed, the plants with the strongest resistance were those in which the introduced gene was silent2. Baulcombe eventually concluded that the introduced gene was co-suppressing both itself and the same gene in the virus. John Lindbo, William Dougherty and their colleagues at Oregon State University in Corvallis, working with the tobacco etch virus, obtained similar results3. Both groups began to suspect that co-suppression had evolved to protect plants from viral attack. The case was strengthened when Baulcombe’s team plus two other groups showed independently that several plant viruses produce proteins that stifle co-suppression4–6. This suggested a classic evolutionary arms race between host and pathogen.