What's in a genome?

December 17, 2012

The species in question is the fruit fly Drosophila mauritiana, a close relative of the well known (and previously sequenced) Drosophila melanogaster that swarms around our fruit bowls in summer. Nolte and colleagues now present a complete genomic sequence, annotating it to indicate the various genes it contains. The information will naturally be extremely useful to all those who are working on this organism.

But the present study goes much, much further. Schlötterer's group has recently developed powerful analytic methods for measuring the genetic variability of populations. In contrast to its widespread cousin, Drosophila mauritiana is only found on the island of Mauritius and it might be expected that the species' highly restricted distribution would lead to a relatively low rate of variability. Surprisingly, however, Nolte and her colleagues found that its genome is highly diverse, with polymorphisms (genetic variation) present across the chromosomes. Interestingly, the polymorphisms are not evenly distributed throughout the genome. Instead, the researchers observed that within the highly variable regions there are two large areas where the sequence is much more highly conserved. Such "troughs in variability" are thought to be the result of selective sweeps: newly arising mutations confer so great a selective advantage on the flies in question that they spread rapidly through the population until they become "fixed", or present in essentially all individuals.

One of the classical tenets of genetics is that when a parent carries two different versions of a gene at a particular locus, each of the so-called alleles has an equal probability of being passed to the next generation. Recently, however, it has become clear that certain genes are able to "cheat" and ensure that they are preferentially transmitted to the offspring. The simplest model involves two genes close together, of which one encodes a poison to which the other confers resistance. The poison kills all the gametes that do not contain the resistance gene, effectively ensuring the rapid spread of the allele in question through the genome. Might the two "troughs in variability" in the Drosophila mauritiana genome have arisen from an intragenomic conflict of this kind? It is hard to answer this question with certainty. However, one of the two troughs that Nolte identified contains the so-called Odysseus gene, which has previously been suggested to be involved in genomic conflict in the closely related Drosophila simulans. The other might relate to a second system characterized in Drosophila simulans.

The fact that two areas of the Drosophila mauritiana genome vary considerably less than surrounding regions suggests that some of the genes present have recently been involved in intragenomic conflicts. And these may indirectly help ensure the species' identity. As Schlötterer explains, "the biggest challenge for a newly separated species is to avoid being subsumed back into the species from which it derived. The weapons used in intragenomic conflicts also work against hybrids with related species so we can speculate that they act as a type of 'speciation gene'. It will be intriguing to study whether this has been the case for the Mauritius fruit flies."
-end-
The paper "Genome-wide Patterns of Natural Variation Reveal Strong Selective Sweeps and Ongoing Genomic Conflict in Drosophila mauritiana" by Viola Nolte, Ram Vinay Pandey, Robert Kofler and Christian Schlötterer is published in the online version of the journal "Genome Research" (doi:10.1101/gr.139873.112). The printed version of the paper will appear in the journal's January 2013 issue.

The scientific article in full text online (Open Access): http://genome.cshlp.org/content/early/2012/11/18/gr.139873.112

About the University of Veterinary Medicine, Vienna

The University of Veterinary Medicine, Vienna is the only academic and research institution in Austria that focuses on the veterinary sciences. About 1000 employees and 2300 students work on the campus in the north of Vienna, which also houses the animal hospital and various spin-off-companies. http://www.vetmeduni.ac.at

Scientific contact
Prof. Christian Schlötterer
Institute of Population Genetics
University of Veterinary Medicine, Vienna
T +43 1 25077-4300
christian.schloetterer@vetmeduni.ac.at

Distributed by
Klaus Wassermann
Public Relations/Science Communication
University of Veterinary Medicine, Vienna
T +43 1 25077-1153
klaus.wassermann@vetmeduni.ac.at

University of Veterinary Medicine -- Vienna

Related Genome Articles from Brightsurf:

Genome evolution goes digital
Dr. Alan Herbert from InsideOutBio describes ground-breaking research in a paper published online by Royal Society Open Science.

Breakthrough in genome visualization
Kadir Dede and Dr. Enno Ohlebusch at Ulm University in Germany have devised a method for constructing pan-genome subgraphs at different granularities without having to wait hours and days on end for the software to process the entire genome.

Sturgeon genome sequenced
Sturgeons lived on earth already 300 million years ago and yet their external appearance seems to have undergone very little change.

A sea monster's genome
The giant squid is an elusive giant, but its secrets are about to be revealed.

Deciphering the walnut genome
New research could provide a major boost to the state's growing $1.6 billion walnut industry by making it easier to breed walnut trees better equipped to combat the soil-borne pathogens that now plague many of California's 4,800 growers.

Illuminating the genome
Development of a new molecular visualisation method, RNA-guided endonuclease -- in situ labelling (RGEN-ISL) for the CRISPR/Cas9-mediated labelling of genomic sequences in nuclei and chromosomes.

A genome under influence
References form the basis of our comprehension of the world: they enable us to measure the height of our children or the efficiency of a drug.

How a virus destabilizes the genome
New insights into how Kaposi's sarcoma-associated herpesvirus (KSHV) induces genome instability and promotes cell proliferation could lead to the development of novel antiviral therapies for KSHV-associated cancers, according to a study published Sept.

Better genome editing
Reich Group researchers develop a more efficient and precise method of in-cell genome editing.

Unlocking the genome
A team led by Prof. Stein Aerts (VIB-KU Leuven) uncovers how access to relevant DNA regions is orchestrated in epithelial cells.

Read More: Genome News and Genome Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.