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The flowering plant uses molecular transporters to release the compounds responsible for their sweet smell, researchers have found.
The scents that flowers emit can attract pollinators and defend against pathogens, but little has been known about how the volatile organic compounds that create scents escape the cells that produce them.
Natalia Dudareva at Purdue University in West Lafayette, Indiana, and her colleagues found a gene that encodes a membrane transporter and is expressed at high levels in Petunia hybrida (pictured) petals when emissions of volatiles reach their peak.
Suppressing expression of the transporter, called PhABCG1, reduced release of the compounds by up to 62%. Biochemical assays showed that PhABCG1 shuttles two of the major volatile compounds emitted by petunias across cell membranes.
30-year-old conjecture about how grains and powders pack holds up.
A computer simulation has found that all jammed arrangements of granular objects — those in which particles such as powders or sand grains are packed together densely enough to be locked in place — are equally probable.
The behaviour of particles as they become jammed and unjammed explains a wide range of phenomena, from the movement of avalanches to the most efficient ways of processing pills. Stefano Martiniani at the University of Cambridge, UK, and his colleagues modelled a material as a two-dimensional collection of circles. They found that when the grains are just dense enough to be jammed — and therefore are on the threshold of coming unjammed — all possible packings are equally likely. This is in contrast to high-density packings and, in particular, to the optimal density, for which only a regular honeycomb pattern is possible. The result supports a conjecture dating back to the 1980s.
Taxonomic shakedown gives manta rays a devil of a time.
Manta rays should no longer be viewed as members of a distinct genus, according to a revision of the taxonomy of these huge fish and the closely related devilrays.
William White at the Commonwealth Scientific and Industrial Research Organisation in Hobart, Australia, and his colleagues conducted a comprehensive genetic analysis of the two recognized Manta species and nine recognized Mobula (devilray) species. Their analysis finds that these animals are much more closely related than has been assumed.
The authors suggest the reef manta, Manta alfredi, and the giant manta, Manta birostris (pictured), should now be known as Mobula alfredi and Mobula birostris, respectively, with the Manta genus no longer valid. The team also proposes that three types of Mobula should no longer be considered stand-alone species.
Mantas and devilrays are under threat in many parts of the world and improved understanding of their taxonomy is crucial for informing conservation strategy, the authors say.
Genetically engineered yeast provides a cheap on-the-spot test for fungal infections.
Fungal infections cause about 2 million human deaths a year, kill wildlife and ruin crops. Early detection could prevent such loss, but typical tests require costly equipment and expertise. Now a team led by Virginia Cornish at Columbia University in New York City has developed a diagnostic test that uses genetically engineered baker’s yeast (Saccharomyces cerevisiae) and costs less than one cent to produce.
The yeast strain turns red when it recognizes short chains of amino acids (peptides) from fungal pathogens that it has been engineered to detect. Incorporated into a dipstick prototype, the strain identified low levels of peptides from fungal pathogens in soil, urine and blood. Among them was Paracoccidioides brasiliensis, a fungus that causes acute pneumonia in Central and South America.
The test could be used in regions that do not have electricity or well-equipped laboratories, and can be stored at room temperature for at least nine months, the authors say.
Sustained exposure to neonicotinoids is harmful to three species of bee.
The levels of neonicotinoid pesticides used by farmers harm honeybee health, say two studies. The controversial chemicals are banned in some countries because of fears over their effects on pollinators, but evidence that they harm bees has been disputed.
Ben Woodcock at the Centre for Ecology and Hydrology near Wallingford, UK, and his colleagues distributed honeybees (Apis mellifera), wild bumblebees (Bombus terrestris) and wild solitary bees (Osmia bicornis) to 33 sites across Germany, Hungary and the United Kingdom. They randomly assigned the bees to sites of oilseed-rape crops that were untreated or treated with neonicotinoids.
In Hungary and the United Kingdom, the pesticides had negative effects on bee health, but some positive effects were seen in Germany. Overall, the authors say, neonicotinoids seem to lower the reproductive success of wild species and honeybees.
In a separate study, Amro Zayed at York University in Toronto, Canada, and his team quantified the amount of neonicotinoids bees were exposed to in Canada’s maize (corn) regions. They found that honeybees were exposed for most of their active season. In experiments mimicking realistic exposure levels, they found that neonicotinoids increased deaths of worker bees and reduced the number of fertile queens.
Most modern horse breeds are descended from oriental stallions imported less than 700 years ago.
Mutations on the Y chromosome can be used to reconstruct male lineages, but low Y-chromosome diversity has made this difficult in horses. Barbara Wallner at the University of Veterinary Medicine Vienna and her colleagues used next-generation deep sequencing of the Y chromosomes of 52 stallions, to investigate the history of modern horses.
They found that almost all of the 21 breeds represented carried a group of variants that appeared around 650 years ago. They fell into two subgroups: one originating in the Arabian Peninsula and the other in the Central Asian steppe. The only exceptions were the Shetland pony, Norwegian fjord horse and Icelandic horse, which branched off around 1,300 years ago.
The import of oriental stallions and modern horse-breeding techniques have had a huge impact on the Y chromosomes of domesticated breeds, the authors note.
Simulation of the Deepwater Horizon oil plume reveals cleaning power of microbial hydrocarbon degraders.
Plumes of oil left in the Gulf of Mexico by the 2010 Deepwater Horizon disaster were consumed by a multitude of carbon-craving microbes.
The disaster released some 650 million litres of crude oil. Plumes of tiny oil droplets formed around 1,500 metres below sea level, but the fate of these droplets has been a mystery.
Gary Andersen at Lawrence Berkeley National Laboratory in California and his colleagues created plumes of oil in natural seawater collected near the disaster site, at a depth of 1,200 metres, and observed how the water’s microbial community evolved. The team identified all the bacteria that fed on the oil droplets, as well as the genes responsible for each species’ ability to break down hydrocarbons.
Understanding the succession of living organisms that metabolize oil at different stages of degradation could help predict clean-up rates for deep-water oil spills, the authors say.
Human migration left few genetic marks on the female population of the Caucasus.
The female gene pool in the southern Caucasus seems little changed since Neolithic times, even though this geographical bridge — part of the old Silk Road trade route between Europe and Asia — has been a crossroads for human migration.
Ashot Margaryan and Morten Allentoft from the Natural History Museum of Denmark in Copenhagen and their colleagues extracted mitochondrial DNA, which is passed from mother to child, from 52 ancient skeletons found in Armenia and a neighbouring region. The samples spanned 7,800 years.
The researchers analysed the DNA sequences and compared them with 206 mitochondrial genomes from modern Armenians. They found that the maternal gene pool remained stable.
Archaeological records show major cultural upheavals in Armenia over the past eight millennia. The results imply that these may have occurred through exchanges of ideas rather than through population shifts, or that it was mainly men who migrated into the region.
Accelerated melting of island’s vast ice sheet is due mainly to clearer skies.
The accelerated surface melting observed on Greenland in recent years is due primarily to the island receiving more summer sunshine.
The Greenland ice sheet has been losing mass since the mid-1990s, both because more ice is being discharged into the sea and as a result of increased melting across its vast surface. Earlier work suggested that higher atmospheric temperatures were the main cause of the rise in surface melting.
But a team led by Stefan Hofer at the University of Bristol, UK, analysed satellite data on cloud cover. Between 1995 and 2009, summer cloud cover over Greenland decreased by nearly 1% per year. Each percentage point represents enough sunshine to melt an extra 27 gigatonnes of ice per year, a computer model suggests. Overall, Greenland lost about 4,000 gigatonnes of ice in the 20 years from 1995, contributing to sea-level rise.
Greenland’s clouds seem to be changing in direct response to atmospheric-circulation changes, which, in turn, are thought to be driven by shrinking Arctic summer sea ice.