Directional selection on body weight and hybrid dysgenesis in Drosophila melanogaster

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Trematominae and Artedidraconinae: contrasted mitogenome evolution for two Antarctic radiations

Cellular respiration has been widely studied in Antarctic teleost fishes because of their peculiar adaptations to an extreme environment. In parallel mitochondrial sequence markers have become highly popular for molecular systematics. However, there are few whole mitochondrial genome sequences published, and none available for some of the subfamilies. Here, we present two large mitogenome datasets including most species and multiple sequences for many species of two subfamilies, Trematominae and Artedidraconinae (Duhamel et al. 2014). These include two highly diverse but very different adaptative radiations, with contrasting divergence dates, morphological polymorphism, and habitat dominance. The sampling is based on a well identified, extensive collection resulting from the 2008 CEAMARC survey and the subsequent REVOLTA surveys in Terre Adélie (IPEV), already DNA barcoded and sequenced in previous studies. The mitogenome sequences for these two subfamilies differ in composition, gene order, and relative divergence of mitochondrial markers, with strong, taxon-specific biases like very high C contents in some regions. The gene order change provides a synapomorphy for the subfamily Trematominae and an interesting development in teleost mitogenomes. The complete Artedidraconinae mitogenomes provide a much higher amount of variable sites (approx*30), while previous sequence datasets were plagued by low informativeness (Lecointre et al. 2011). As already established on single mitochondrial genes, intraspecific variability is lower than interspecific variability within each subfamily, however interspecific variability in Artedidraconinae is lower or similar to intraspecific variability in Trematominae. This expanded dataset confirms the unusual evolution of the mitochondrial coded sequences involved in the cellular respiration in Antarctic Nototheniidae, as well as the usefulness of complete mitochondrial genomes for their systematics. The two level multiplexing (Timmermans et al. 2010) and next generation sequencing of long PCR amplicons (following Hinsinger et al. 2015) is efficient to obtain large mitogenomic datasets representative of both inter- and intraspecific variability, key to the understanding of mitochondrial evolution and a step closer to resolving the relationships among these taxa.RECTO (Refugia and Ecosystem Tolerance in the Southern Ocean, BR/154/A1/RECTO

High-order Harmonic Spectroscopy of the Cooper Minimum in Argon: Experimental and Theoretical Study

We study the Cooper minimum in high harmonic generation from argon atoms using long wavelength laser pulses. We find that the minimum in high harmonic spectra is systematically shifted with respect to total photoionization cross section measurements. We use a semi-classical theoretical approach based on Classical Trajectory Monte Carlo and Quantum Electron Scattering methods (CTMC-QUEST) to model the experiment. Our study reveals that the shift between photoionization and high harmonic emission is due to several effects: the directivity of the recombining electrons and emitted polarization, and the shape of the recolliding electron wavepacket.Comment: 13 page

Insights into metazoan evolution from <i>Alvinella pompejana</i> cDNAs

BackgroundAlvinella pompejana is a representative of Annelids, a key phylum for evo-devo studies that is still poorly studied at the sequence level. A. pompejana inhabits deep-sea hydrothermal vents and is currently known as one of the most thermotolerant Eukaryotes in marine environments, withstanding the largest known chemical and thermal ranges (from 5 to 105°C). This tube-dwelling worm forms dense colonies on the surface of hydrothermal chimneys and can withstand long periods of hypo/anoxia and long phases of exposure to hydrogen sulphides. A. pompejana specifically inhabits chimney walls of hydrothermal vents on the East Pacific Rise. To survive, Alvinella has developed numerous adaptations at the physiological and molecular levels, such as an increase in the thermostability of proteins and protein complexes. It represents an outstanding model organism for studying adaptation to harsh physicochemical conditions and for isolating stable macromolecules resistant to high temperatures.ResultsWe have constructed four full length enriched cDNA libraries to investigate the biology and evolution of this intriguing animal. Analysis of more than 75,000 high quality reads led to the identification of 15,858 transcripts and 9,221 putative protein sequences. Our annotation reveals a good coverage of most animal pathways and networks with a prevalence of transcripts involved in oxidative stress resistance, detoxification, anti-bacterial defence, and heat shock protection. Alvinella proteins seem to show a slow evolutionary rate and a higher similarity with proteins from Vertebrates compared to proteins from Arthropods or Nematodes. Their composition shows enrichment in positively charged amino acids that might contribute to their thermostability. The gene content of Alvinella reveals that an important pool of genes previously considered to be specific to Deuterostomes were in fact already present in the last common ancestor of the Bilaterian animals, but have been secondarily lost in model invertebrates. This pool is enriched in glycoproteins that play a key role in intercellular communication, hormonal regulation and immunity.ConclusionsOur study starts to unravel the gene content and sequence evolution of a deep-sea annelid, revealing key features in eukaryote adaptation to extreme environmental conditions and highlighting the proximity of Annelids and Vertebrates

Laser-Induced Electron Diffraction in Chiral Molecules

Strong laser pulses enable probing molecules with their own electrons. The oscillating electric field tears electrons off a molecule, accelerates them, and drives them back toward their parent ion within a few femtoseconds. The electrons are then diffracted by the molecular potential, encoding its structure and dynamics with angstrom and attosecond resolutions. Using elliptically polarized laser pulses, we show that laser-induced electron diffraction is sensitive to the chirality of the target. The field selectively ionizes molecules of a given orientation and drives the electrons along different sets of trajectories, leading them to recollide from different directions. Depending on the handedness of the molecule, the electrons are preferentially diffracted forward or backward along the light propagation axis. This asymmetry, reaching several percent, can be reversed for electrons recolliding from two ends of the molecule. The chiral sensitivity of laser-induced electron diffraction opens a new path to resolve ultrafast chiral dynamics

Eukaryote DIRS1-like retrotransposons: an overview

<p>Abstract</p> <p>Background</p> <p>DIRS1-like elements compose one superfamily of tyrosine recombinase-encoding retrotransposons. They have been previously reported in only a few diverse eukaryote species, describing a patchy distribution, and little is known about their origin and dynamics. Recently, we have shown that these retrotransposons are common among decapods, which calls into question the distribution of DIRS1-like retrotransposons among eukaryotes.</p> <p>Results</p> <p>To determine the distribution of DIRS1-like retrotransposons, we developed a new computational tool, ReDoSt, which allows us to identify well-conserved DIRS1-like elements. By screening 274 completely sequenced genomes, we identified more than 4000 DIRS1-like copies distributed among 30 diverse species which can be clustered into roughly 300 families. While the diversity in most species appears restricted to a low copy number, a few bursts of transposition are strongly suggested in certain species, such as <it>Danio rerio </it>and <it>Saccoglossus kowalevskii</it>.</p> <p>Conclusion</p> <p>In this study, we report 14 new species and 8 new higher taxa that were not previously known to harbor DIRS1-like retrotransposons. Now reported in 61 species, these elements appear widely distributed among eukaryotes, even if they remain undetected in streptophytes and mammals. Especially in unikonts, a broad range of taxa from Cnidaria to Sauropsida harbors such elements. Both the distribution and the similarities between the DIRS1-like element phylogeny and conventional phylogenies of the host species suggest that DIRS1-like retrotransposons emerged early during the radiation of eukaryotes.</p

Bursts of retrotransposons and extensive chromosomal repatterning within the Antarctic teleost fish species flock Trematominae

21st International Colloquium on Animal Cytogenetics and Gene Mapping (ICACGM), Naples, ITALY, JUN 07-10, 2014International audienceno abstrac