A new generation of insect resistant GM crops: transgenic wheat synthesising the aphid alarm signal

当蚜虫（绿蝇）受到捕食者的攻击时，它们会发出警告信号，提醒其他邻近的蚜虫。这是通过一种叫做警报信息素的化学物质来实现的，其他蚜虫可以闻到这种化学物质。这种报警信息素是完全无毒的，即使在水平远远高于将在这个项目中使用。除了由蚜虫产生外，它还由一些非作物植物自然产生。这样的植物之一是薄荷，我们已经分离出的基因负责生产纯蚜虫报警信息素薄荷植物。通过将这种基因插入到其他植物中，我们可以使它们产生信息素，最近我们用一种被生物学家广泛用作模型的简单植物塔勒进行了这种转化。当我们这样做时，蚜虫害虫不再被转化的水芹吸引。此外，天然昆虫控制得到改善，因为蚜虫的关键天敌，称为寄生虫，在转化的塔勒水芹上寻找蚜虫的时间更长。在这一成功之后，我们现在需要对小麦进行类似的转化，小麦是一种全球重要的作物，最终利用这一系统控制蚜虫害虫，并培育新一代环境友好的转基因作物。其他害虫也有信息素，这里开发的方法应该导致在其他作物中用无毒的昆虫行为信号化学品取代有毒杀虫剂的可能性。研究最初将在封闭的实验室条件下进行，然后扩展到严格控制的田间试验。我们建议用蚜虫报警信息素基因转化小麦植株，检查转化的小麦植株是否散发信息素，然后检查对蚜虫害虫及其天敌的影响。叶片上的蚜虫群将暴露于转化小麦的气味中，并记录蚜虫逃逸的比例。然后，将使用称为嗅觉计的特殊装置，让蚜虫和它们的拟寄生虫在从转化的小麦中通过的空气或空白气流之间进行选择。我们预计，蚜虫将被正常的小麦气味所吸引，但被转化植物的气味所排斥，并且蚜虫寄生性天敌将更被转化小麦所吸引。还将转化植物上的寄生虫行为与正常植物上的行为进行比较。田间模拟容器将用于测量正常和转化小麦上的蚜虫定居。一旦我们在实验室条件下确定了最有前途的小麦品种，我们将在户外进行田间试验。在生长季节，每周将对每小区100株植物的样本中的蚜虫数量进行计数。我们预计蚜虫在转化的小麦植株上的定居将减少，并且任何定居的蚜虫将更容易受到天敌的攻击。蚜虫驱避气味和天敌吸引力的组合效应将意味着转化的小麦植物上较低的蚜虫侵染。这将为未来减少农作物杀虫剂的使用提供一种新的选择。

When aphids (greenfly) are attacked by predators they release a warning signal to alert other neighbouring aphids. This is achieved by a chemical called an alarm pheromone that other aphids can smell. This alarm pheromone is completely non-toxic, even at levels far higher than would be used in this project. As well as being produced by aphids, it is produced naturally by some non-crop plants. One such plant is peppermint and we have isolated the gene responsible for the production of pure aphid alarm pheromone in peppermint plants. By inserting this gene into other plants we can make them produce the pheromone and we have recently performed this transformation with a simple plant called thale cress which is widely used by biologists as a model. When we did this aphid pests were no longer attracted to the transformed cress. Furthermore, natural insect control was improved because a key natural enemy of aphids, called a parasitoid, searched for aphids for a longer period of time on the transformed thale cress. Following this success we now need to carry out a similar transformation with wheat, a crop plant of worldwide importance, so as eventually to exploit this system for aphid pest control and breed a new generation of environmentally friendly GM crops. Other insect pests also have pheromones and the approach developed here should lead to possibilities for replacing toxic insecticides with non-toxic insect behaviour signal chemicals in other crops too. Studies will initially be conducted under contained laboratory conditions and then extended to carefully regulated field trials. We propose to transform wheat plants with the aphid alarm pheromone gene, check that the transformed wheat plants are emitting the pheromone and then examine the effects on aphid pests and their natural enemies. Groups of aphids on leaves will be exposed to the odour of the transformed wheat and the proportion of aphids scuttling away will be recorded. Special devices called olfactometers will then be used to give aphids and their parasitoids a choice between air passing from the transformed wheat or a blank airflow. We expect that aphids will be attracted to normal wheat odour but repelled by odours of the transformed plants and that the aphid parasitoids will be more attracted to the transformed wheat. Parasitoid behaviour on the transformed plants will also be compared with behaviour on normal plants. Field simulator containers will be used to measure aphid settlement on normal and transformed wheat. Once we have identified the most promising wheat varieties under lab conditions we will test them outdoors in field plot trials. Aphid numbers will be counted in samples of 100 plants per plot every week during the growing season. We expect that aphid settlement will be reduced on the transformed wheat plants and that any aphids that do settle will be more exposed to attack by natural enemies. The combined effect of an aphid repellent odour and attraction of natural enemies will mean lower aphid infestations on the transformed wheat plants. This will provide a new option for reducing insecticide use on crops in the future.