转基因抗虫基因存在交叉耐受

美国转基因

转基因抗虫基因存在交叉耐受

[明辨是非] 从生物进化和和生态学的常识判断，美国昆虫学家和生物技术负责人的结论是正确的，转基因逼迫害虫进化，最终吃亏的是人类本身。让人气愤的是，人类中的部分唯利是图的小人，他们所犯的错误要拉全人类买单，他们靠谎言靠打击异己者苟延残喘，可惜纸总包不住火，站起来说真话的科学家越来越多了。全人类眼睛擦亮之日，就是转基因骗子原形毕露之时。大自然能够纠正人类的错误吗？能，但需要时间，需要代价。昆虫在地球存在的3.5-5亿年，人类的历史短短三五百万年，人类不懂得谦虚，必将遭到报复。




http://blog.sina.com.cn/s/blog_4b7683ce0102er7s.html


     尽管转基因技术给一些作物抗虫带来了显著效果，最近科学家发现能有效控制虫害的基因能迅速引起抗毒病虫的滋生，说明农业目前病不能离开传统的例如轮作种植防虫技术。
     爱荷华州立大学昆虫学家Aaron Gassmann最近研究发现，在爱荷华州土壤中存在的一种西方玉米根虫能对三种BT毒素中的两种产生交叉耐受，BT毒素是最近开发成功的转基因抗植物病虫作物蛋白，这一最新研究提示这种转基因作物具有潜在的风险，因为如果这种昆虫对其中一种产生耐受，也能同时对另一种产生耐受。这一研究本周发表在PNAS上。而这两种转基因作物恰好就是目前已经进入市场的转基因品种。2003年美国政府批准的第一个被批准的抗虫基因是Bt toxin Cry3Bb1，2009年有农民发现这种转基因玉米存在根虫害，2011年这种问题在另外一种mCry3A转基因玉米也被发现。Gassmann的研究发现，这两种转基因存在交叉耐受，说明即使同时使用两种转基因改良也无法避免这种虫害。产生这种交叉耐受的原因是这种昆虫的胃内存在结合这些毒素的蛋白，而两种毒素存在类似的分子结构，可能是同一种蛋白产生两种耐受的原因。
     另外一种可能是这种昆虫有的类型非常顽固，玉米的毒素剂量不足以杀死。
     Bt毒素能杀死99.99%的欧洲玉米螟，但根虫仍可以存活2%。这种耐受力强的根虫可以迅速进化，在短短几年内在一块土地内迅速扩散。例如在爱荷华州大约需要3.6年。
     美国陶氏全球生物技术科学政策负责人Nicholas Storer认为，这个研究说明，单纯用转基因技术，如果不结合传统的防治手段，耐药病虫可以迅速在某一土地上发展。美国陶氏等农业技术公司现在正开发具有两种转基因的聚合品种，他们和孟山都联合生产的有两种转基因的品种没有发现任何耐受现象。
     Gassmann说这种联合转基因是对抗耐受的重要手段，但一旦出现对其中一种毒素耐受，这种联合效应会大大折扣。所以，农民不能单纯依靠这种转基因技术来对抗害虫，而应该联合传统的防虫手段，例如轮换种植的方式。例如，这种玉米根虫在没有玉米生长的土地上无法生存。
     Storer同意即使最好的技术也应该和其他手段联合应用，玉米轮作是对抗根虫的传统有效手段，看来现在要重新启用这种古老方法。

Naturedoi:10.1038/nature.2014.14887

《自然》报告《美国科学院刊》论文：转基因不敌害虫，传统轮种控虫有效
Pests worm their way into genetically modified maize
Broadening of rootworm resistance to toxins highlights the
importance of crop rotation.

Brian Owens
17 March 2014
Article toolsRights & Permissions

Biosphoto/FLPA
Defending fields from the rapid adaptation of western corn rootworm
to transgenic toxins may require weapons beyond those of
biotechnology.
Expand
Even with biotech crops, farmers still need to make use of age-old
practices such as crop rotation to fight insect pests.
That’s the lesson to be drawn from the latest
discovery of resistance to the pest-fighting toxins added to maize
— also known as corn.


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According to a team led by Aaron Gassmann, an entomologist at Iowa
State University in Ames, in some Iowa fields a type of beetle
called the western corn rootworm (Diabrotica virgifera virgifera
LeConte) has developed resistance to two of the three types of
Bacillus thurinigiensis (Bt) toxin produced by genetically modified
maize. Resistance to one type of Bt toxin has cropped up in the
worms in recent years, but now there is a twist —
the researchers have found that resistance to that type of Bt toxin
also confers protection against another, more recently introduced
type. Their work appears in this week's Proceedings of the National
Academy of Sciences1.

“That’s two of the three toxins
on the market now,” says Gassmann.
“It’s a substantial part of the
available technology.”

Genetically modified (GM) maize producing the Bt toxin Cry3Bb1,
which provided protection against pests such as rootworm, was first
approved for use in the United States in 2003. By 2009, farmers had
started to see rootworm damage in their GM crops. In 2011, that
damage had spread to GM maize containing a second toxin, mCry3A. In
lab tests, Gassmann showed that this was a case of cross-resistance
— worms that had become resistant to Cry3Bb1 were
also resistant to mCry3A, possibly because the toxins share
structural similarities and some binding sites in the
insect’s gut.

Part of the problem is that rootworms are tough, and the Bt maize
does not produce enough toxin to fully control them. The Bt toxins
used against pests such as the European corn borer (Ostrinia
nubilalis) kill more than 99.99% of their targets, whereas more
than 2% of rootworms can survive Bt maize. Resistance in the worms
can evolve rapidly in fields where the same kind of maize is grown
every year — in Iowa it showed up after an
average of 3.6 years.

Related stories
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Case studies: A hard look at GM crops
More related stories
Nicholas Storer, a global science-policy leader for biotechnology
at Dow AgroSciences in Washington DC, says that the study
illustrates that if GM crops are not used as part of an integrated
pest-management policy, resistance can develop quickly in an
individual field. Agricultural biotechnology companies such Dow are
now ‘pyramiding’ their seeds so
that they produce two different Bt toxins to attack the rootworm.
For example, Dow has teamed up with Monsanto of St Louis, Missouri,
to sell seeds that combine Cry3Bb1 with Cry34/35Ab1, a toxin that
has so far not seen any resistance develop.

Gassmann says that the pyramiding of toxins is an important way to
delay the development of resistance, but that the combination is
less effective once resistance arises to one of the toxins. So
farmers should not rely exclusively on technology to fight pests,
and should instead periodically change the crop grown on a field to
help disrupt the pest’s life cycle.
“The rootworm can’t survive if
the corn’s not there,” Gassmann
says.

Storer agrees that even the best technologies will always need to
be combined with the old methods. “Crop rotation
was the primary tool to combat rootworm before Bt came
along,” he says. “We need to
keep it up.”

Nature doi:10.1038/nature.2014.14887
References
孙学军译文
转基因抗虫基因存在交叉耐受 精选
已有 716 次阅读 2014-3-18 13:18 |个人分类:自然科学|系统分类:海外观察

尽管转基因技术给一些作物抗虫带来了显著效果，最近科学家发现能有效控制虫害的基因能迅速引起抗毒病虫的滋生，说明农业目前病不能离开传统的例如轮作种植防虫技术。

爱荷华州立大学昆虫学家Aaron Gassmann最近研究发现，在爱荷华州土壤中存在的一种西方玉米根虫能对三种BT毒素中的两种产生交叉耐受，BT毒素是最近开发成功的转基因抗植物病虫作物蛋白，这一最新研究提示这种转基因作物具有潜在的风险，因为如果这种昆虫对其中一种产生耐受，也能同事对另一种产生耐受。这一研究本周发表在PNAS上。而这两种转基因作物恰好就是目前已经进入市场的转基因品种。2003年美国政府批准的第一个被批准的抗虫基因是Bt toxin Cry3Bb1，2009年有农民发现这种转基因玉米存在根虫害，2011年这种问题在另外一种mCry3A转基因玉米也被发现。Gassmann的研究发现，这两种转基因存在交叉耐受，说明即使同时使用两种转基因改良也无法避免这种虫害。产生这种交叉耐受的原因是这种昆虫的胃内存在结合这些毒素的蛋白，而两种毒素存在类似的分子结构，可能是同一种蛋白产生两种耐受的原因。

另外一种可能是这种昆虫有的类型非常顽固，玉米的毒素剂量不足以杀死。

Bt毒素能杀死99.99%的欧洲玉米螟，但根虫仍可以存活2%。这种耐受力强的根虫可以迅速进化，在短短几年内在一块土地内迅速扩散。例如在爱荷华州大约需要3.6年。

美国陶氏全球生物技术科学政策负责人Nicholas Storer认为，这个研究说明，单纯用转基因技术，如果不结合传统的防治手段，耐药病虫可以迅速在某一土地上发展。美国陶氏等农业技术公司现在正开发具有两种转基因的聚合品种，他们和孟山都联合生产的有两种转基因的品种没有发现任何耐受现象。

Gassmann说这种联合转基因是对抗耐受的重要手段，但一旦出现对其中一种毒素耐受，这种联合效应会大大折扣。所以，农民不能单纯依靠这种转基因技术来对抗害虫，而应该联合传统的防虫手段，例如轮换种植的方式。例如，这种玉米根虫在没有玉米生长的土地上无法生存。

Storer同意即使最好的技术也应该和其他手段联合应用，玉米轮作是对抗根虫的传统有效手段，看来现在要重新启用这种古老方法。

Naturedoi:10.1038/nature.2014.14887