Lateral gene transfer, a tool to reconstruct the “family tree” of species Today, it is known that lateral gene transfer is a common way – in addition to transmission of genes from parents to offspring – for unicellular organisms, bacteria and certain eukaryotes to diversify their genetic makeup. This feature is also a source of information on the timing of evolution: any transfer must be between species that are contemporary. French researchers have developed a computer model that can calculate all the lateral transfers within a given group of species, and help trace the history of its evolution. Proceedings of the National Academy of Sciences October 2012 online 17 A glimpse of the diversity of protists found in ocean plankton. Only 75,000 species have been described so far, out of the tens of millions that may remain to be discovered. Genetic bar codes to shed light on protists Little is known about protists, single-cell organisms that first appeared a billion years ago. And yet they produce much of the oxygen we breathe, and cause diseases such as malaria. To shed light on this facet of biodiversity, an international consortium including French researchers has launched a large-scale campaign to classify protists using high-throughput DNA sequencing techniques. The scientists hope to describe several tens of millions of species, as opposed to a mere 75,000 today. PLOS Biology November 2012 online Fly’s dependence on a cactus elucidated Researchers have discovered why a fly species (Drosophila pachea) has become dependent on a cactus in the Sonoran Desert in Mexico. They identified mutations that have modified one of the Drosophila’s genes, which normally transforms cholesterol into steroid hormones that are essential for the fly’s survival. The mutations have made the fly dependent on a derivative of cholesterol that is only found in one plant in the region, the Senita cactus, while also improving the insect’s survival rate on the plant. Science September 2012 Single DNA molecule repair observed in real time Ultraviolet light or tobacco smoke can cause changes to the DNA in our cells, which may lead to the onset of cancers. Now, scientists in France, the UK and the US have succeeded in observing in real time the initial stages in one of the DNA repair mechanisms of cells, known as TCR. To do this, they used a novel technique for the nanomanipulation of a single DNA molecule in a bacterial model. Nature September 2012 online Replication of Lentille virus (in red), a giant virus of the Mimiviridae family, and of its virophage, Sputnik 2 (in green). New giant virus and its “mobilomes” discovered Mobile genetic elements, otherwise known as “mobilomes”, are DNA fragments that can move within and between genomes. A new giant virus belonging to the family Mimiviridae has just been identified by a team of French researchers, who have found that it is associated with two mobile genetic elements: a virophage (a virus that infects other viruses), which can become integrated into its genome, and a new element that can be transposed from one virus to the other which they have dubbed a “transpoviron”. Proceedings of the National Academy of Sciences October 2012 online 2012 A year at CNRS
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