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The generation of complex colour patterns on animals' bodies is thought to depend on reaction-diffusion mechanisms involving diffusible local activators (morphogens) and long-range inhibitors. Using the spectacular polka-dot wing pattern of Drosophila guttifera as a model, Sean Carroll and colleagues show experimentally that the wing spots are induced by the Wingless morphogen. In composite cover image, the left wing is wild-type D. guttifera, showing the sixteen vein-associated spots and four intervein shades, and the right a double-transgenic variant, merging vein spot and intervein shade cis-regulatory element activity. Image by Thomas Werner, Shigeyuki Koshikawa and Nicolas Gompel
A conduit from the Red Sea could restore the disappearing Dead Sea and slake the region's thirst. But such a massive engineering project could have untold effects, reports Josie Glausiusz.
After years of wrangling over the chemical's toxicity, researchers are charting a new way forwards. Brendan Borrell investigates how the debate has reshaped environmental-health studies.
Current national emissions targets can't limit global warming to 2 °C, calculate Joeri Rogelj, Malte Meinshausen and colleagues — they might even lock the world into exceeding 3 °C warming.
Engineering biological systems and organisms is a costly team effort and may be incompatible with an open-source regulatory environment, finds Michael A. Goldman.
Most insulin-secreting pancreatic β-cells are irreplaceably lost in type 1 diabetes. In a mouse model, pancreatic α-cells seem to sacrifice their identity to replenish the low stock of β-cells1. Two experts discuss what this means for understanding the basic cell biology involved and its relevance to treating diabetes.boxed-text
Entanglement between particles permits the quantum uncertainty in one variable to be reduced at the cost of increasing that in another. Condensates are an ideal system in which this technique can be studied.
The neocortex of the mammalian brain mediates functions such as sensory perception and ultimately consciousness and language. The spread of local signals across large distances in this brain region has now been clarified.
Unlike its neighbours on the right-hand side of the periodic table, boron barely forms an anion. A new trick has been established that allows it to do so, enabling a highly unusual complex to be prepared.
Droplets of a liquid alloy on a silicon surface can rearrange the surface atoms so that they mimic the short-range ordering of atoms in the alloy. Remarkably, this effect inhibits freezing of the droplets.
Proteins are synthesized by ribosomes, and then commonly undergo further modifications. A new example of how these host-cell processes can e subverted by a pathogenic bacterium has come to light.
The ability to perceive Earth's magnetic field, which at one time was dismissed as a physical impossibility, is now known to exist in diverse animals. The receptors for the magnetic sense remain elusive. But it seems that at least two underlying mechanisms exist — sometimes in the same organism.
Here, the generation and evolution of the complex spotted wing pattern of Drosophila guttifera are investigated. The findings show that wing spots are induced by the Wingless morphogen, and that the elaborate spot pattern evolved from simpler schemes by co-option of Wingless expression at new sites. This type of process is likely to occur in other animals, too.
In the pancreas, insulin-producing β-cells are long-lived and generally replicate seldom. They can do so, however, after increased metabolic demand or after injury. Here, a new transgenic model is developed in which β-cells are nearly completely ablated in mice. If given insulin, these mice survive, and grow new β-cells. Lineage-tracing shows that these new β-cells come from α-cells, revealing a previously disregarded degree of pancreatic cell plasticity.
A common anatomical feature of the sensory cortex in many species is that neurons with similar features cluster into vertically orientated domains spanning all layers of the cortex. Moreover, neurons in one domain modulate neurons in neighbouring domains through horizontal connections. A combination of techniques has now been used to show that such horizontal projections suppress layers of cortex devoted to processing inputs, but facilitate layers devoted to outputs.
Here, the atmosphere of the extrasolar planet GJ 436b is studied during its 'secondary eclipse'. The findings reveal the presence of some H2O and traces of CO2. The best-fit compositional models contain a high CO abundance and a substantial methane deficiency relative to thermochemical equilibrium models for the predicted hydrogen-dominated atmosphere. Disequilibrium processes such as vertical mixing and polymerization of methane may be required to explain this small methane-to-CO ratio.
The precision of interferometers — used in metrology and in the state-of-the-art time standard — is generally limited by classical statistics. Here it is shown that the classical precision limit can be beaten by using nonlinear atom interferometry with Bose–Einstein condensates.
Atom chips provide a versatile quantum laboratory for experiments with ultracold atomic gases, but techniques to control atomic interactions and to generate entanglement have been unavailable so far. Here, the experimental generation of multi-particle entanglement on an atom chip is described. The technique is used to produce spin-squeezed states of a two-component Bose–Einstein condensate, which should be useful for quantum metrology.
Supercooling is a phenomenon by which a liquid remains in its fluid phase well below its melting point. Supercooling can be inhibited by the presence of a solid surface, whereby crystalline surfaces cause adjacent atoms in the liquid to become ordered, inducing crystal nucleation of the melt. Here it is shown that a particular surface ordering of gold atoms on top of a silicon substrate can stabilize the liquid phase of a gold-silicon eutectic droplet, and thus enhance supercooling.
The accumulation of nitrate in freshwater and coastal marine ecosystems is one of the consequences of the worldwide production of artificial fertilizers. Here it is shown that nitrate accumulation in ecosystems shows consistent and negative nonlinear correlations with organic carbon availability, along a continuum from soils, through freshwater systems and coastal margins, to the open ocean. This pattern can be explained by carbon:nitrate ratios, which influence nitrate accumulation by regulating microbial processes.
It is generally accepted that specific neuronal circuits in the brain's cortex drive behavioural execution, but the relationship between the performance of a task and the function of a circuit is unknown. Here, this problem was tackled by using a technique that allows many neurons within the same circuit to be monitored simultaneously. The findings indicate that enhanced correlated activity in specific ensembles of neurons can identify and encode specific behavioural responses while a task is learned.
Variation in the regulation of gene transcription between individuals is thought to be a major cause of phenotypic diversity. Here, individual differences in the binding of transcription-factor proteins are studied. A well-known transcription factor in the yeast pheromone pathway is used as an example, and the underlying genetic loci responsible for variation in its binding are mapped. The study reveals new insights into the mechanisms of gene regulation, and new regulators of the yeast pheromone pathway.
SUMOylation is a post-translational protein modification that affects many eukaryotic cellular processes. It is shown here that cellular infection with Listeria monocytogenes induces degradation of one of the essential SUMOylation enzymes, Ubc9, through a mechanism that involves a bacterial toxin, listeriolysin O. This effect on SUMOylation may support efficient infection by Listeria.
During embryonic development, blood vessels remodel in response to blood flow. Here, a genetic pathway is described through which this mechanosensory stimulus is integrated with early developmental signals to remodel vessels of the aortic arch in zebrafish. It is found that the flow-induced transcription factor klf2a is required to induce the expression of an endothelial-specific microRNA, activating signalling through the growth factor Vegf.
Fibrillar deposits of tau protein (neurofibrillary tangles) are thought to cause neuronal death in patients with Alzheimer's disease, and tau-related frontotemporal dementia. Here, however, the opposite has been found: the activation of executioner caspase enzymes occurs first, preceding tangle formation by hours to days. Tangle-bearing neurons seem to be long-lived, indicating that tangles might be 'off pathway' to acute neuronal death.
The fat mass and obesity-associated (FTO) gene has been associated with increased body weight. The FTO protein has DNA/RNA demethylase activity. Here, the crystal structure of human FTO in complex with the mononucleotide 3-methylthymidine is presented. The structure provides a basis for understanding the substrate specificity of FTO, and should serve as a foundation for the design of FTO inhibitors.
During photosynthesis, light energy is used by photosystems I and II to establish electron flow, which ultimately results in the production of ATP and NADPH. Two modes of electron flow exist, a linear electron flow and a cyclic electron flow (CEF). The latter pathway generates more ATP, but its molecular components have been elusive. Here, a combination of biochemical and spectroscopic techniques has been used to identify the supercomplex that drives CEF in the green alga Chlamydomonas reinhardtii.
Most agents that generate breaks in DNA leave 'dirty ends' that cannot be joined immediately; instead, intervening steps are required to restore the integrity of nucleotides at the break. Here it is shown that the non-homologous end joining pathway requires a 5′-dRP/AP lyase activity to remove abasic sites at double-strand breaks. Surprisingly, this activity is catalysed by the Ku70 protein, which, together with its partner Ku86, had been thought only to recognize broken DNA ends and to recruit other factors that process ends.
X-ray crystallography has become the most common way for structural biologists to obtain the three-dimensional structures of proteins and protein complexes. However, crystals of large macromolecular complexes often diffract only weakly (yielding a resolution worse than 4 Å), so new methods that work at such low resolution are needed. Here a new method is described by which to obtain higher-quality electron density maps and more accurate molecular models of weakly diffracting crystals.
The scientific community now seems convinced that small RNAs will become therapies, if new tools can help these large molecules to make it safely into cells. Monya Baker reports.