VOA慢速英语--基因编辑用来阻止蚊子识别目标的能力

Gene¹ Editing Used to Block Mosquitos’ Ability to Identify Targets

Scientists say they have used gene editing to block the ability of mosquitos to identify human targets.

The method is described in a new study led by American researchers. The scientists say the study could lead to major developments in the fight against mosquito-borne diseases such dengue, yellow fever and Zika.

Such diseases -- carried by the Aedes aegypti mosquito -- kill hundreds of thousands of people each year.

The researchers say their study is the first to closely examine the way mosquitoes use their sight to identify targets to bite. The study was recently published in Current Biology.

The research centered on the Aedes aegypti mosquito, which bites during the daytime. Other kinds of mosquitos, including Anopheles, hunt mostly at night. Anopheles are responsible for spreading malaria².

Female Aedes aegypti search out blood meals in humans to develop eggs. They use several different senses to find those meals. One of the main identifying tools is the smell of carbon dioxide (CO2). When a human breathes out CO2, the mosquitoes become more active and begin looking for targets to bite.

The research team said this search generally begins with the mosquito flying toward the direction of the released CO2. When seeking out targets, the insects search for dark objects. Once the mosquitoes are within close range, they can also sense heat from skin and additional skin smells to help guide them to a human.

The researchers used the CRSPR/Cas-9 gene editing method to remove two out of five light-sensing receptors in the mosquitoes' eyes. They say taking away these receptors blocked the ability of the female Aedes aegypti to recognize dark targets.

Craig Montell is a professor at the University of California, Santa Barbara, who helped lead the research. He said in a statement that by removing the two eye receptors, the team was able to "eliminate CO2-induced target recognition without causing blindness."

Experiments were carried out with the mosquitoes in cages and in wind tunnels. The team observed the insects' movements toward light or dark markers to confirm that the gene editing method had changed their behavior.

In cage tests, the mosquitoes that did not undergo gene editing sought out a round, black marker after sensing CO2. But the mosquitoes with the two receptors removed did not attempt to move to the black marker even with the presence of CO2.

The team then carried out a series of tests to confirm that the gene-edited mosquitoes had not simply gone blind. The experiments involved observing the insects' reactions to light, as well as taking voltage measurements from electrodes connected to their eyes.

The results of those tests showed that the gene-edited mosquitoes could not only still see, but they could also identify different shades and motion.

Another leader of the study was Yinpeng Zhan, a postdoctoral researcher at the University of California, Santa Barbara. He said the research findings could have a wide effect on a series of insect disease carriers that can harm humans.

"Vision plays an important role in detecting a potential host for blood-feeding insects such as mosquitoes, kissing bugs³, tsetse flies and ticks," Zhan said. "And this study is the first to uncover the molecular⁴ mechanisms⁶ behind this behavior."

Next, the team says it will seek to identify other receptors used by Aedes mosquitoes to search out and feed on human targets.

Words in This Story

eliminate – v. to remove or take away

induce – v. to cause a particular condition

cage – n. a container used to keep birds or animals

tunnel – n. a round, enclosed passageway

shade – n. a color, especially as related to how dark or light it is

vision – n. the act of power of seeing

detect – n. to discover or notice something

mechanism⁵ – n. a part of a piece of equipment that does a particular job

1 gene   

n.遗传因子，基因

参考例句：

• A single gene may have many effects.单一基因可能具有很多种效应。
• The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。

2 malaria   

n.疟疾

参考例句：

• He had frequent attacks of malaria.他常患疟疾。
• Malaria is a kind of serious malady.疟疾是一种严重的疾病。

3 bugs   

adj.疯狂的，发疯的n.窃听器( bug的名词复数 )；病菌；虫子；[计算机]（制作软件程序所产生的意料不到的）错误

参考例句：

• All programs have bugs and need endless refinement. 所有的程序都有漏洞，都需要不断改进。 来自《简明英汉词典》
• The sacks of rice were swarming with bugs. 一袋袋的米里长满了虫子。 来自《简明英汉词典》

4 molecular   

adj.分子的；克分子的

参考例句：

• The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
• For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时，分子的碰撞就停止了。

5 mechanism   

n.机械装置；机构，结构

参考例句：

• The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
• The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。

6 mechanisms   

n.机械( mechanism的名词复数 )；机械装置；[生物学] 机制；机械作用

参考例句：

• The research will provide direct insight into molecular mechanisms. 这项研究将使人能够直接地了解分子的机理。 来自《简明英汉词典》
• He explained how the two mechanisms worked. 他解释这两台机械装置是如何工作的。 来自《简明英汉词典》