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
Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Cholera bacteria infect more effectively with a simple twist of shape
13.01.2017 | Princeton University
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction