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A Danaean gift is one which brings misfortune to the receiver. The most famous example is probably the Trojan horse, which the Greeks - or "Danaeans" - used to bring about the fall of Troy. Such cunning is also known in the field of biology. While working on an international study, published in the latest issue of the prestigious journal of research, "Science", researchers in Münster have turned up a surprise: jewel wasps carry a gene of the parasitic bacteria Wolbachia in their genetic make-up. The question the researchers are now asking is: Is this gene a Danaean gift?
The international consortium of scientists headed by Prof. Jack Werren from the University of Rochester and Prof. Stephen Richards from Baylor College (USA) have carried out comprehensive tests on the genome of three closely related types of jewel wasps of the "Nasonia" species. The results will enable the researchers to gain fundamental insights which might be transferable to other species too - for example, in one important area of evolutionary biology: the interplay between hosts and parasites.
One widespread parasite, the Wolbachia bacterium, lives in the bodies of numerous types of insects, including jewel wasps. The bacteria's progeny is passed on via the host's egg cells and thus infects the host's own offspring. "Wolbachia manipulates insects and other arthropods on a grand scale," says Dr. Arndt Telschow from the Institute of Evolution and Biodiversity at the University of Münster, who is working on the study together with Prof. Erich Bornberg-Bauer. "In order for Wolbachia to multiply in an optimum way it influences the procreation of its hosts using a variety of methods. For example, in many species it targets and kills all male offspring."
In the case of jewel wasps, Wolbachia changes the sperm in such a way that egg cells which are not infected with bacteria die after insemination. Researchers have observed that wasps afflicted with Wolbachia cannot procreate with closely related species. "If the bacteria are killed by using an antibiotic, however, procreation succeeds without any problem," says Prof. Bornberg-Bauer. "Here we see that Wolbachia also influences the emergence of species."
As Dr. Telschow says, "What is highly interesting from the point of view of evolutionary biology is the fact that we have now proven the existence of a DNA section in the genome of jewel wasps. It's a fine example of the labyrinthine paths that evolution can take." At an earlier stage of evolution, say the Münster scientists, this DNA section was exchanged between Wolbachia bacteria and pox viruses. "We know that this gene helps the pox viruses to change the immune system of their hosts to their own advantage," says Prof. Bornberg-Bauer, "and we assume that this 'gift' also contributes to Wolbachia's ability to multiply in an optimum way in the jewel wasp." There is, however, one difference to the Trojan horse: the evolutionary interplay between wasps and bacteria does not end with the Danaean gift - unlike the Trojan War.
Reference: Werren J. H. et al. (2010): Functional and Evolutionary Insights from the Genomes of Three Parasitoid Nasonia Species. Science Vol. 327. no. 5963, pp. 343 - 348; DOI: 10.1126/science.1178028
http://www.sciencemag.org/cgi/content/full/327/5963/343 Science/reference
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