An international team headed up by researchers from the University of Zurich has discovered the gene that determines the male sex in houseflies. Surprisingly, the sex-determining mechanisms are not the same for all houseflies – they depend on where the insects live. This knowledge not only helps us better understand the evolution of sex determination, but also aids in the control of agricultural pests or carriers of disease.
Sex is one of the most essential characteristics of an individual – not only for humans, but also for animals and plants. All organisms that reproduce sexually are usually clearly male or female, whereby the genetic control mechanism responsible for sex determination varies widely from species to species. In humans, women have two X chromosomes in the cell nuclei, while men have an X and a Y chromosome. The Y chromosome carries the SRY gene, which determines the male sex. This gene developed about 150 million years ago during the evolution of the mammals.
Sex determination depends on the housefly habitat
Many different sex-determining mechanisms prevail among insects. Flies in particular are well suited for examining the evolution of this variety. The wide-spread housefly (Musca domestica) is very unusual in this regard: Depending on where they live, they use different methods for sex determination. In northern latitudes, females have X chromosomes, while males have an X and a Y chromosome. Here, as well, the Y chromosome carries a gene that determines maleness. In southern latitudes, on the other hand, houseflies do not have a Y chromosome. The male-determining gene lies on one of the other five chromosomes.
The gene responsible for determining maleness in houseflies has been unknown until now. Together with colleagues from Groningen (the Netherlands) and Göttingen (Germany), the group of researchers led by Daniel Bopp of the Institute of Molecular Life Sciences of the University of Zurich has succeeded in identifying this gene. With genetic tricks, the scientists created offspring of the same sex and could then search for genes that were already active early in the development of males.
If the male-determining gene is temporarily switched off, males become “pregnant”
According to developmental biologist Bopp, one gene stood out during these analyses: “When this gene temporarily loses its function during early development, ‘pregnant’ males filled with mature eggs result.” In case of a total functional loss of the gene, the male even completely turns into a female that is capable of sexual reproduction. The newly discovered gene is called “Mdmd” (Musca domestica male determiner). It is relatively large and very similar to a known gene, CWC22. Researchers assume that Mdmd arose from a duplication of the CWC22 gene.
Development of new sex-determining mechanisms
In the case of houseflies from southern latitudes, the gene that determines maleness lies on a so-called proto-sex chromosome. This chromosome has apparently assumed a prime role in sex determination only recently from an evolutionary viewpoint. “With our work, we were able to demonstrate that new sex chromosomes arise when existing genes like Mdmd move from the Y chromosome to another chromosome,” Daniel Bopp says. After the change of location, the Y chromosome is lost and the new sex chromosome with the Mdmd gene assumes the function of determining the male sex.
Before the beginning of this research, no gene for maleness was known in insects until now. In the meantime, corresponding genes have been found in two mosquito species. The Mdmd gene of the housefly, however, has no similarity with the two mosquito genes. This proves how varied sex determination can be in different species and how fast the genetic program responsible for the development of males and females changes within the course of evolution.
New pest control strategies
The latest discoveries of the basic genetic principles for sex determination are valuable not just for evolutionary biology. This knowledge is also very useful for developing new, sustainable strategies for pest control. When specially bred, sterile insect males are released, they compete with the wild males for the females. After the repeated release of several million males, the natural population in the affected region collapses. The technology has already been used successfully against fruit pests in agriculture. In the future, they will also be able to be used in the control of disease carriers, like mosquitoes or houseflies. Daniel Bopp emphasizes, “Fundamental research with houseflies can therefore be of great benefit for society.”
Akash Sharma, Svenia D. Heinze, Yanli Wu, Tea Kohlbrenner, Ian Morilla, Claudia Brunner, Ernst A. Wimmer, Louis van de Zande, Mark D. Robinson, Leo W. Beukeboom, Daniel Bopp. Male sex in houseflies is determined by Mdmd, a paralog of the generic splice factor gene CWC22. Science. 12 May 2017. doi:10.1126/science.aam5498
Daniel Bopp, PhD
Institute of Molecular Life Sciences
University of Zurich
Phone: +41 44 635 48 69
Kurt Bodenmüller | Universität Zürich
Colorectal cancer risk factors decrypted
13.07.2018 | Max-Planck-Institut für Stoffwechselforschung
Algae Have Land Genes
13.07.2018 | Julius-Maximilians-Universität Würzburg
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
13.07.2018 | Event News
13.07.2018 | Materials Sciences
13.07.2018 | Life Sciences