The coming of summer brings promise for humans and insects alike. The farmer planted maize for a bountiful harvest, but the European Corn Borer (ECB) is looking for a good meal right away. The caterpillars of this pest bore deep into the maize stems, where they eat the inner pith causing the weakened stalks to fall over before the ears can ripen. As if one pest were not bad enough, there are even two different races, called E and Z that have a subtle difference in the shape of their pheromones.
(NATURE, Advance Online Publication, 30.6.2010, DOI 10.1038/nature09058)
All over the world farmers fight the ECB with insecticides, genetically modified plants, or biological pest control. The moth with the scientific name Ostrinia nubilalis is native to Europe and was introduced to North America early in the last century, where it received its common name. The E- and Z-races were discovered in the 1970s when synthetic pheromones gave very different results in attracting males in Iowa and New York. The Z-race, now widespread in the western USA, mainly attacks maize, whereas insects of the E-race specialize on Artemisia and other plants.
The two races don't interbreed in the field, and the chemical structure of the sex pheromone holds the key
The ECB sex pheromone, called 11-tetradecenylacetate, contains a long zig-zag tail of 14 carbon atoms, with one double bond. This can be in the E (trans) configuration, or alternatively the Z (cis) configuration which causes the tail to bend at that point. This seemingly small structural variation makes a big difference at mating time. When an ECB female of the Z-race is ready to mate, she releases the E and Z isomers in a ratio of 3:97, and only Z-race males are attracted. E-females emit the same isomers but in a ratio of 98:2, and this attracts only E-race males, “In evolutionary biology this is called a ‘reproductive isolation barrier’; which is interesting because it can mark the beginning of the evolution of new species,” Jean-Marc Lassance, first author of the study, explains.
A difference in enzymes (reductases) is responsible for the different E and Z ratios
“However, these two races are still far away from a development into new species, and this was actually a crucial advantage for our genetic analyses,” says Astrid Groot from the Max Planck Institute for Chemical Ecology, who has been studying sex pheromones of moths since 2001. “Although they wouldn't find each other in the field, if we put males and females of different races together in the lab, mating occurs and fertile offspring are produced. This allowed us to map the gene controlling this difference in female pheromone production." This gene mapped to a different chromosome from the desaturase enzyme that first introduces the E or Z double bond into the 14-carbon tail, but to the same chromosome as the reductase enzyme that later produces the final pheromone. Intriguingly, there are many differences in the amino acid sequences of the reductases isolated from the E or Z races. When Jean-Marc Lassance measured enzyme activities, he found that even though both races create the E and Z 14-carbon tail in nearly equal amounts, the reductase from E-race females mainly converted the E-form to the final pheromone, and the Z-race reductase converted mostly the Z-form. So a difference in the respective reductase enzymes is responsible for the different E and Z ratios released by the female pheromone glands.
Reason for the development of the two races unclear
This new finding explains only half of the story, since the reason that E and Z males exhibit such strong preferences for E-rich and Z-rich pheromone blends produced by the females is still unknown. “We can only speculate here. We have known for a long time that the gene responsible for pheromone production in females and the gene controlling male response are different; in fact they occur on different chromosomes. And we still don't understand how selection could act on two independent genes to initiate the development of the two races,” says Christer Löfstedt from Lund University, Sweden. The researchers are now turning their attention to mapping the male-response gene based on additional crosses.
Pheromone traps and “mating disruption”
As well as giving insight on the evolution of new species, the pheromones of insect pests can also be manipulated for crop protection. As soon as their chemical structure is elucidated, they can be chemically synthesized and applied in pheromone traps. These can be used as a sensitive method to monitor the population sizes of pest populations, or to catch and kill large numbers of males intent on mating. Another method is "mating disruption", where synthetically produced pheromones are widely dispersed in the field, swamping out the weaker signals of individual females, which the disoriented males cannot locate. These methods are especially useful when insecticides must be avoided, such as in control of codling moth in apple orchards, or trapping large numbers of bark beetles to protect forests. Because very low amounts of species-specific sex pheromones are sufficient to lure or confuse male insects which respond even to the slightest pheromone concentrations in the air, these methods are in particular environmentally friendly. [JWK, DH]Original Publication:
NATURE, Advance Online Publication, 30.6.2010, DOI 10.1038/nature09058Further Information:
Astrid Groot, David Heckel, Department of Entomology, Max Planck Institute for Chemical Ecology; Tel.: +49 (0)3641 57 1501; firstname.lastname@example.org, email@example.com
Dr. Jan-Wolfhard | Max-Planck-Institut
Cancer diagnosis: no more needles?
25.05.2018 | Christian-Albrechts-Universität zu Kiel
Less is more? Gene switch for healthy aging found
25.05.2018 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)
The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.
Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...
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...
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...
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...
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...
25.05.2018 | Event News
02.05.2018 | Event News
13.04.2018 | Event News
25.05.2018 | Event News
25.05.2018 | Machine Engineering
25.05.2018 | Life Sciences