Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Bacterial Toxins Against Resistant Insect Pests

19.10.2011
Scientists from the USA, Mexico, China, and Germany have developed Bt toxins for the management of resistance in European corn borer and other crop pests.

Toxins from Bacillus thuringiensis bacteria (Bt toxins) are used in organic and conventional farming to manage pest insects. Sprayed as pesticides or produced in genetically modified plants, Bt toxins, used in pest control since 1938, minimize herbivory in crops, such as vegetables, maize or cotton.


Tobacco budworm (Heliothis virescens)
Melanie Marr, MPI for Chemical Ecology


Cotton bollworm (Helicoverpa armigera)
Suyog Kuwar, MPI for Chemical Ecology

Since 1996, Bt producing transgenic crops have been grown, which successfully control pests like the European corn borer, the tobacco budworm, the Western corn rootworm, and the cotton bollworm. Over the years, Bt resistant insects have emerged in organic and conventional farming. Scientists have therefore modified the molecular structure of two Bt toxins, Cry1Ab and Cry1Ac, in order to overcome resistance. The novel toxins, Cry1AbMod and Cry1AcMod, are effective against five resistant insect species, such as the diamondback moth, the cotton bollworm, and the European corn borer. Cry1AbMod and Cry1AcMod can be used alone or in combination with other Bt toxins for plant protection. (NATURE Biotechnology, advance online publication, DOI: 10.1038/nbt.1988)

New insights into the mechanisms of action of Cry1Ab and Cry1Ac served as the basis for development of the modified Bt toxins. The primary question had been why the Cry proteins, which naturally occur in B. thuringiensis, have such a resoundingly toxic effect on many different herbivorous insects. Researchers had previously found a protein in the caterpillars’ midgut that binds Bt toxins – with fateful consequences for the insects, because binding the toxins causes the gut cells to die. This protein is one of the many types of cadherin proteins in the cell. Binding to cadherin also causes the removal of a structural element of the Cry protein called an alpha helix, which triggers cell death; this is probably due to a Cry-mediated formation of pores in the cell membranes.

Scientists in the groups of David G. Heckel at Clemson University, South Carolina, USA, and at the University of Melbourne, Australia, then discovered that mutated cadherins cause Bt resistance. If cadherin mutations or the absence of cadherin were the causal factors of Bt resistance in certain pest insects, it should be possible to break this resistance by means of Bt toxins that did not have the crucial alpha helix and could therefore be effective without cadherin. Mexican researchers led by Mario Soberón and Alejandra Bravo developed these novel toxins, called Cry1AbMod and Cry1AcMod.

“When we studied the new Bt toxins in 12 resistant and non-resistant strains of five major pest species, the results of our experiments were encouraging but surprising. The new toxins are also effective against strains whose Bt resistance is not based on cadherin mutations,” says David G. Heckel, director of the Department of Entomology at the Max Planck Institute for Chemical Ecology in Jena, Germany, and co-author of the study. Especially interesting was the finding that the new toxins were specifically effective against a super-resistant strain of tobacco budworm carrying both the cadherin mutation and another mutation affecting an ABC transporter which was discovered by the Max Planck researchers last year.

Particularly striking was the effect of Cry1AbMod and Cry1AcMod on a Bt resistant corn borer and a resistant diamondback moth strain that was 350 times stronger compared to that of the natural toxins. On the other hand, the new toxins had only a weak effect on some strains whose Bt resistance is due to a mutated cadherin.

If both novel Bt toxins prove to be useful in agriculture, they can be used in combination with different Bt toxins to guarantee a reliable effect on herbivorous pests. Biologists also agree that measures to reduce the occurrence of resistant insect pests must be strictly adhered to and that farmers should be informed in detail. Such measures would mainly include the use of different pesticides, crop rotation, and simultaneous sowing of non-Bt plants in fields, where transgenic Bt varieties are grown. [JWK, AO]

Original Publication:
Tabashnik, B. E., Huang, F., Ghimire, M. N., Leonard, B. R., Siegfried, B. D., Rangasamy, M., Yang, Y., Wu, Y., Gahan, L. J., Heckel, D. G., Bravo, A., Soberón, M. (2011). Efficacy of genetically modified Bt toxins against insects with different genetic mechanisms of resistance. NATURE Biotechnology. doi: 10.1038/nbt.1988.
Further Information:
David G. Heckel, MPI for Chemical Ecology, Jena
Tel.: 03641 - 57 1500, heckel@ice.mpg.de
Picture Material:
Angela Overmeyer M.A., Tel. 03641 - 57 2110, overmeyer@ice.mpg.de
or Download via http://www.ice.mpg.de/ext/735.html

Dr. Jan-Wolfhard Kellmann | Max-Planck-Institut
Further information:
http://www.ice.mpg.de
http://www.ice.mpg.de/ext/735.html

More articles from Life Sciences:

nachricht Complementing conventional antibiotics
24.05.2018 | Goethe-Universität Frankfurt am Main

nachricht Building a brain, cell by cell: Researchers make a mini neuron network (of two)
23.05.2018 | Institute of Industrial Science, The University of Tokyo

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

Im Focus: Dozens of binaries from Milky Way's globular clusters could be detectable by LISA

Next-generation gravitational wave detector in space will complement LIGO on Earth

The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

 
Latest News

When corals eat plastics

24.05.2018 | Ecology, The Environment and Conservation

Surgery involving ultrasound energy found to treat high blood pressure

24.05.2018 | Medical Engineering

First chip-scale broadband optical system that can sense molecules in the mid-IR

24.05.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>