2016
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How plants manage excess solar energy
Life on earth largely depends on the conversion of light energy into chemical energy through photosynthesis by plants. However, absorption of excess sunlight can damage the complex machinery responsible for this process. Researchers from the AV短视频 (UNIGE), Switzerland, have discovered how Chlamydomonas reinhardtii, a mobile single-cell alga, activates the protection of its photosynthetic machinery. Their study, published in the journal PNAS, indicates that the receptors (UVR8) that detect ultraviolet rays induce the activation of a safety valve that allows dissipation of excess energy as heat. A second protective role is thus attributed to these receptors, whose ability to induce the production of an anti-UV “sunscreen” had already been shown by the Geneva team.
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New study reveals West Antarctica’s largest glacier started retreating in 1940s
Present-day thinning and retreat of Pine Island Glacier, one of the largest and fastest shrinking glaciers of the West Antarctic Ice Sheet, was initiated by warming associated with strong El Niño activity during the 1940s. The new finding provides the first direct evidence and timing of glacier retreat prior to satellite records.
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How mammary glands appeared in the course of evolution
A joint team of geneticists from the AV短视频 (UNIGE) and the Swiss Federal Institute of Technology in Lausanne (EPFL), Switzerland, demonstrated that the emergence of mammary glands in placental mammals and marsupials results from recycling certain ‘architect’ genes. The latter, known as Hox genes, are responsible for coordinating the formation of the organs and limbs during the embryonic stage. Such genes are controlled by complex regulatory networks. In the course of evolution, parts of these networks were reused to produce different functions. Architect genes were thus requisitioned to form the mammary bud and, later, for gestation. This team’s work has been published in the journal PNAS.
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Selectively conductive or insulating
Some materials hold surprising — and possibly useful — properties: Neodymium nickel oxide is either a metal or an insulator, depending on temperature. This characteristic makes the material a potential candidate for transistors in modern electronic devices. To understand how neodymium nickel oxide makes the transition from metal to insulator and vice versa, researchers at the Paul Scherrer Institute (PSI) and the AV短视频 (UNIGE) have precisely probed the distribution of electrons in the material. By means of a sophisticated development of X-ray scattering, they were able to show that electrons in the vicinity of the material’s oxygen atoms are rearranging. The researchers have published their study in the journal Nature Communications.
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A lead to overcome resistance to antibiotics
Pseudomonas aeruginosa is a common bacterium of our environment. It can however become a formidable pathogen causing fatal infections, especially in intubated patients, people suffering from cystic fibrosis or severe burns. The presence of certain metals in the natural or human environment of the bacterium makes it more dangerous and, in particular, resistant to antibiotics of last resort. A team of researchers from the AV短视频 (UNIGE), Switzerland, has shown that a specific protein of P. aeruginosa, called Host factor q (Hfq), is essential for reacting to these metals and acquire these new properties. The results, presented in the special issue Virulence Gene Regulation in Bacteria of the journal Genes, single out the Hfq protein as the Achilles heel of P. aeruginosa. Indeed, blocking its action could make this pathogen unable to adapt to a new environment and to resist to certain antibiotics.
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Repress to better control
Researchers at the AV短视频 have uncovered an epigenetic mechanism that prevents the activation of numerous genes, including those involved in the growth of breast cells. Our DNA is compacted into the cell nucleus thanks to its winding around millions of proteins called nucleosomes. When a gene must be transcribed to produce proteins, the nucleosomes present must be temporarily ejected to enable the gene to be unwrapped. A team of biologists from the AV短视频 (UNIGE), Switzerland, studied the functioning of nucleosomes associated with genes activated by estrogens, which drive the growth of breast cells. They discovered that the stability of these nucleosomes, namely their tendency to be ejected, is determined by a biochemical modification on some of their components, called histones H2Bub1. The details of this new epigenetic mechanism - which modifies DNA without affecting the sequence - are published in the journal Molecular Cell.
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The oldest rock on Earth
The paper « No evidence for Hadean continental crust within Earth’s oldest evolved rock unit » of Reimink et al. in Nature Geoscience presents the first high-precision U-Pb date of a Hadean (>4.0 Ga old) zircon in the Acasta Gneisses of NW Canada. The authors provide evidence that the earliest rocks on Earth were formed by fractional crystallization from a basaltic melt in a pre-plate tectonic context.
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The end justifies the means, even at the cellular level
Cells destroy part of their pre-messenger RNAs to produce appropriate amounts of a protein called CIRBP. Each of our cells is endowed with a miniature clock composed of a set of ‘clock genes’. During the day, the expression of these genes varies, and this fluctuation influences many biological functions, including body temperature. In turn, our body temperature acts on the daily production of a protein called CIRBP, which will reinforce the activation of certain clock genes. The loop is thus completed. A team of biologists at the AV短视频 (UNIGE), in collaboration with researchers at the Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland, deciphered how, in this complex loop, the cell succeeds in producing the right amount of CIRBP protein during the day. This protein plays an essential role in the development of certain cancers, as it can activate or inhibit the proliferation of malignant cells. The results on temperature-dependent CIRBP gene expression are published in the journal Genes & Development.
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Barcodes to identify gene regulators
The same DNA is present in every cell of an organism, but only some genes are expressed in a given cell. These genes are activated by proteins called transcription factors, in response to various biological signals. Transcription factors thus regulate most of the cellular processes, both in health and disease. A group of biologists from the AV短视频 (UNIGE), Switzerland, has developed a novel technology to identify all the transcription factors involved in any process and in response to any signal. The applications of this method, published in the journal Genes & Development, are virtually unlimited, whether in the medical field or that of basic biology.
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Superconductivity: after the scenario, the staging
Superconductivity with a high critical temperature (high Tc) continues to present a theoretical mystery. While this phenomenon is experimentally well established, no scientist has managed to explain its mechanism. In the late 90’s, the British physicist Anthony Leggett proposed a scenario based on the Coulomb energy. Today, researchers at the AV短视频 (UNIGE), Switzerland, in collaboration with Leggett and his group, committed to test this scenario. Their findings challenge Leggett’s conjecture, opening new avenues for the explanation of high Tc superconductivity. These results are available in the journal Physical Review X.
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How do plants protect themselves against sunburn?
To protect themselves against type B ultraviolet rays (UV-B), which are highly harmful, plants have developed cellular tools to detect them and build biochemical defenses. A team of biologists from the AV短视频 (UNIGE), Switzerland, discovered the existence of a UV-B receptor a few years ago. Today, these researchers demonstrate how these receptors, once activated by UV-B, associate with proteins that assist them to be assembled in the cell nucleus and to develop responses for survival and acclimation. This study is published in the journal PNAS.
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A new wave of antimalarial drugs in preparation
Malaria caused by the parasite Plasmodium falciparum remains a major public health problem worldwide. As a continuation of previous research targeting Hsp90, a universal molecular chaperone performing vital functions both in the parasite and in human cells, researchers at the AV短视频 (UNIGE) and of Basel, Switzerland, have developed a strategy to identify molecules capable of inhibiting the parasite’s protein and causing the destruction of the pathogen, without affecting mammalian cells. The study is published in the Journal of Medicinal Chemistry.
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Hairs, feathers and scales have a lot in common !
The potential evolutionary link between hairs in mammals, feathers in birds and scales in reptiles has been debated for decades. Today, researchers of the AV短视频 (UNIGE) and the SIB Swiss Institute of Bioinformatics, Switzerland, demonstrate that all these skin appendages are homologous: they share a common ancestry. On the basis of new analyses of embryonic development, the Swiss biologists evidenced molecular and micro-anatomical signatures that are identical between hairs, feathers and scales at their early developmental stages. These new observations, published today in Science Advances, indicate that the three structures evolved from their common reptilian ancestor.
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Understanding the resistance to treatments against breast cancer
Researchers from UNIGE reveal a mechanism of resistance to the anti-estrogenic drug tamoxifen. Estrogens are responsible for the survival and proliferation of tumor cells in 70% of all breast cancer cases. The most frequently used treatment to fight this variety of tumors relies on anti-estrogens such as tamoxifen. However, nearly a third of the patients develop a resistance to this type of therapy after a few years. In a study published in the journal Nucleic Acids Research, biologists from the AV短视频 (UNIGE), Switzerland, reveal how tumor cells become refractory to the drug. They succeeded in identifying eight factors involved in the process of resistance to the treatment. The researchers also suggest various approaches for developing new therapies.
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A positive step towards negative capacitance
An international collaboration involving researchers from the AV短视频 and colleagues from England, Spain, France and Luxembourg has demonstrated that destabilising the spontaneous polarisation of a special class of materials known as ferroelectrics gives rise to the phenomenon of negative capacitance that could one day lead to transistors with reduced power consumption. This research is published in the Journal Nature.
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Switzerland winds up superconductivity
For the first time in Europe, the Swiss have achieved a fully superconductive coil able to reach a magnetic field of 25 Tesla. The unusual electronic properties of some superconducting materials permit lossless and dense electrical currents at very low temperatures, even in high magnetic fields. Conductors made of these materials are thus ideal for winding coils to generate very high magnetic fields, which are essential for a number of applications like magnetic medical imaging, magnetic resonance spectroscopy for the analysis of complex molecules or even accelerator magnets. To generate ever-higher magnetic fields, physicists at the AV短视频 (UNIGE) and an R&D team of Bruker BioSpin in Fällanden (ZH), both in Switzerland, started a collaboration in 2012, which was partially funded by the Swiss National Science Foundation (SNSF). Together, they successfully developed and tested the first superconducting coil able to reach a magnetic field of 25 Tesla. A first in Europe.
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The transition between the arm and the hand occurs thanks to a genetic switch
During embryonic life, the emergence of body limbs is orchestrated by a family of architect genes, which are themselves regulated by two DNA structures. While the first presides over the construction of the arm, the other takes over for the development of the hand. Geneticists from the AV短视频 (UNIGE) and the Swiss Federal Institute of Technology in Lausanne (EPFL), Switzerland, show that the same architect proteins, called HOX13 and acting together, complete the formation of the arm and initiate that of the hand, allowing to connect the two processes. As for the region located between the arm and the hand, it escapes the attention of the two regulatory DNA structures, thus providing an opportunity for the wrist bones to develop. The study is published in the journal Genes & Development.
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A plant cell recycles its resources in times of scarcity
To cope with changes in its aquatic environment and the nutrient deficiencies that may result, Chlamydomonas reinhardtii, a mobile single-cell alga, must adapt its metabolism for subsistence, notably in terms of sugar. The latter is produced by photosynthesis. To this end, plants and algae use internal cell structures called chloroplasts, which are equipped with protein complexes, the photosystems. If certain nutrients are missing, such as iron, the alga temporarily dismantles its photosystems to recycle some of their components. Researchers at the AV短视频 (UNIGE), Switzerland, have identified a protein that plays a distinctive role in this recycling. Their results are described in the journal The Plant Cell.
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Bacterial virulence is stimulated by burns
Sepsis constitutes the main cause of disease and death in people suffering from severe burns. This results from the dissemination of pathogens in the body, including Pseudomonas aeruginosa, one of the three bacteria most frequently responsible for this complication. This microorganism is all the more fearsome as its virulence and its resistance to antibiotics can be modulated by various factors present in its host. Researchers led by Karl Perron, microbiologist at the Faculty of the sciences of the AV短视频 (UNIGE), Switzerland, studied the effect of exudates - biological fluids that seep out of burn wounds - on the survival and the virulence of these three bacteria. The results, published in the journal mSphere of the American Society for Microbiology, demonstrate that Pseudomonas aeruginosa has the capacity to multiply within these human fluids and that some of its virulence factors are even overexpressed. The scientists also made a detailed analysis of the composition of exudates. These data will enable them to develop an artificial culture medium and an in vitro system to analyze the initial steps of burn wound infections, to better counter them.
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Generation of « tailored » magnetic materials
Every day, new technologies require more precision in the intrinsic properties of the materials used. To meet increasingly specific requirements, physicists are interested in a generation of artificial materials, the properties of which can be controlled. Researchers at the AV短视频 (UNIGE), Switzerland, in collaboration with French and English teams, have succeed in manipulating the properties of two oxides which make up the artificial material, more exactly they managed to modify the magnetic properties which can be either ferromagnetic or antiferromagnetic; that is, with or without net magnetic moment. The scientists have demonstrated, in their study published in Nature Communications, that they are able now to control the magnetism in this type of materials and that they could, in the near future, offer tailored materials for the devices of tomorrow.
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A cellular sensor of phosphate levels
Signaling molecules regulate the uptake of this essential cell nutrient. Inorganic phosphate is an essential building block of cell membranes, DNA and proteins. It is also a main component of ATP, the “cell currency” of energy transfer. All cells therefore need to maintain a sufficient concentration of phosphate in their cytoplasm and have developed systems to transport and store this nutrient. But how does a cell know how much phosphate it actually needs? Researchers from the AV短视频 (UNIGE) and the AV短视频 of Lausanne (UNIL), Switzerland, report that a region of specific proteins, the so-called SPX domain, signals the phosphate status to fungal, plant and human cells. This domain provides a binding surface for small molecules that regulate the uptake of the nutrient into the cell. Their findings, which now appear in Science, could contribute to the development of crops that use phosphate more efficiently.
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Unveiling the withering process
A hormone activates organ shedding in plants. During their life, plants constantly renew themselves. They sprout new leaves in the spring and shed them in the fall. No longer needed, damaged or dead organs such as blossoms and leaves are also cast off by a process known as abscission. By doing so, plants conserve energy and prepare for the next step in their life cycle. But how does a plant know when it is the right time to get rid of unnecessary organs? Researchers from the AV短视频 (UNIGE) and the AV短视频 of Oslo (UiO) now shed light on this process. It is regulated by receptor proteins located at the surface of specific cells that form a layer around the future break point. When it is time to shed an organ, a small hormone binds to this membrane receptor and, together with a helper protein, the abscission process is initiated. Their findings are now published in the journal eLife.
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Graphene is both transparent and opaque to radiation
Graphene ensures data fidelity for future wireless devices. A microchip that filters out unwanted radiation with the help of graphene has been developed by scientists from the EPFL and tested by researchers of the AV短视频 (UNIGE). The invention could be used in future devices to transmit wireless data ten times faster.
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Super-conductivity seen in a new light
Superconducting materials have the characteristic of letting an electric current flow without resistance. The study of superconductors with a high critical temperature discovered in the 1980s remains a very attractive research subject for physicists. Indeed, many experimental observations still lack an adequate theoretical description. Researchers from the AV短视频 (UNIGE) in Switzerland and the Technical AV短视频 Munich in Germany have managed to lift the veil on the electronic characteristics of high-temperature superconductors. Their research, published in Nature Communications, show that the electronic densities measured in these superconductors are a combination of two separate effects. As a result, they propose a new model that suggests the existence of two coexisting states rather than competing ones as was postulated for the past thirty years. A small revolution in the world of superconductivity.
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A new role for vitamin B6 in plants
Vitamin B6, which exists in different natural forms called vitamers, is essential for all living organisms, as it participates in numerous aspects of cells’ everyday life. Researchers from the AV短视频 (UNIGE), Switzerland, have discovered an unexpected role for this micronutrient, in relation to nitrogen metabolism. Described in the journal The Plant Cell, the results indicate that one of the vitamers informs the plant of its content in ammonium, a basic nitrogen compound needed for the biosynthesis of various molecules essential for life, such as proteins. In the future, vitamin B6 could be used to ascertain the nitrogen status of plants and eventually prevent the overuse of nitrogen-containing fertilizers that are currently having detrimental effects on the environment.
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A new era for electronic materials
Impressive scientific developments are changing the way in which we look at electronic materials. For many different substances, it is now possible to realize perfect crystals only one or a few atom thick, whose electronic properties can be controlled in ways that would have been considered as science fiction only a few years ago. The latest discovery comes from the AV短视频. A team of researchers succeeded in realizing transistors that turn a monolayer of MoS2 – an insulating material that does not spontaneously conduct electricity – into a material enabling current to flow without dissipating any power, i.e. a superconductor.
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Increase in volcanic eruptions at the end of the ice age
Scientists from Caltech, the AV短视频 of Cambridge, the AV短视频 and ETH Zurich explain how climate change can influence the frequency of volcanic eruptions. Melting of ice and drainage of water into the oceans decreases the pressure applied on the Earth’s mantle, where magmas are generated. This in turn can enhance magma productivity at depth, which eventually intensify volcanic eruptions and degassing.
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A step towards quantum electronics
Work of physicists at the AV短视频 (UNIGE), Switzerland, and the Swiss Federal Institute of Technology in Zurich (ETHZ), in which they connected two materials with unusual quantum-mechanical properties through a quantum constriction, could open up a novel path towards both a deeper understanding of physics and future electronic devices. Their results have just been published in the journal Science.
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A wax shield to conquer the Earth
Seeds have recycled a plant protection mechanism, the cuticle, to withstand terrestrial aggressions. Having emerged late during evolution, seeds have transformed many plants into miniature travelers, contributing greatly to their colonization of terrestrial habitats. Researchers at the AV短视频 (UNIGE), Switzerland, have just discovered one of the keys of this success: the cuticle. Present as a thick waxy layer in the seed coat and composed of cutin - a type of fatty acid -, the cuticle increases seeds’ viability, their resistance to reactive oxygen species, and contributes to maintaining their dormant state. Seeds have thus recycled an ancient terrestrial plant protection mechanism that allows their leaves to be covered with an impermeable film preventing excessive transpiration. The results are published in the journal PLoS Genetics.