The Stanford University researchers have been working long hours honing a three-dimensional printing process to make biomaterials like wood and enamel out of mere clumps of cells. Pundits say such 3D bioprinting has vast potential, and could one day be widely used to transform specially engineered cells into structural beams, food, and human tissue. Rothschild and Gentry don’t only see these laboratory-created materials helping only doctors and Mars voyagers. They also envision their specific research – into so-called “synthetic biomaterials” – changing the way products like good-old-fashioned wooden two-by-fours are made and used by consumers.
Here’s their plan: Rothschild, an evolutionary biologist who works for NASA and teaches astrobiology at Stanford, and Gentry, her doctoral advisee who is trained in biology and mechanical engineering, are working with $100,000 they received last fall from the space agency’s Innovative Advanced Concept Program. They say they’re on track to prove their concept by October: a three-dimensional printing process that yields arrays of cells that can excrete non-living structural biomaterials like wood, mineral parts of bone and tooth enamel. They’re building a massive database of cells already in nature, refining the process of engineering select cells to make and then excrete (or otherwise deliver) the desired materials, and tweaking hardware that three-dimensionally prints modified cells into arrays that yield the non-living end products.
“Cells produce an enormous array of products on the Earth, everything from wool to silk to rubber to cellulose, you name it, not to mention meat and plant products and the things that we eat,” Rothschild said. “Many of these things are excreted (from cells). So you’re not going to take a cow or a sheep or a probably not a silk worm or a tree to Mars. But you might want to have a very fine veneer of either silk or wood. So instead of taking the whole organism and trying to make something, why couldn’t you do this all in a very precise way – which actually may be a better way to do it on Earth as well – so that you’re printing an array of cells that then can secrete or produce these products?”
Rothschild and Gentry’s setup is different from using basic 3D printers that deliver final products. Instead, the NASA-funded researchers are using 3D printing as an enabling technology of sorts. Their setup involves putting cells in a gelling solution with some sort of chemical signaling and support into a piezoelectric print head that spits out cells that form a gel-based 3D pattern.
Andrew Hessel, a biotechnology analyst who is a distinguished researcher with San Rafael, Calif.-based Autodesk Inc., said the emerging field of 3D bioprinting is a “pretty wide open space” with different researchers “all dancing on multiple fronts at once.” And the research is not without controversy. Information-technology research firm Gartner, Inc. recently predicted 3D printing of living tissue and organs will soon spur a major ethical debate.
Hessel said the most-complex 3D bioprinting research is being done with the actual engineering of cells. Companies like Organovo, for example, aren’t actually engineering the cells, and instead are differentiating and laying them in a way that they can mature and grow in to functional tissue.
In an interview with Kirsten Brøchner of the Arthur Hotel Group in Copenhagen, Denmark, we discussed their journey to become the first carbon-neutral hotel group in the world, and how their 5-point climate action plan is not only good for the planet, but good for business. Rahim Kanani: Tell me a little bit about [...]
It is well known that genes are passed from one generation to the next. In addition, new genes arise regularly, although the number of genes in a particular organism does not seem to increase. The paradox has been solved by recent research at the University of Veterinary Medicine, Vienna, which shows ...
Shivering is not an activity many of us enjoy. We do it because we are cold and uncomfortable. But perhaps the news that it could have some of the same benefits as moderate bouts of exercise will stop us running in from the cold so quickly. Researchers have found that the act of shivering can stimulate the conversion of energy-storing “white fat” into energy-burning “brown fat”.
The findings, published in Cell Metabolism, show that when humans shiver their levels of hormones irisin (produced by muscle) and FGF21 (produced by brown fat) increase. Specifically, around 10-15 minutes of shivering by volunteers placed in temperatures of less than 15°C resulted in equivalent rises in irisin as an hour of moderate exercise.
Irisin, identified just two years ago in animals, converts white fat into brown fat. Unlike white fat, brown fat is designed to produce heat by burning calories. For example, around 50g of white fat retains more than 300 kilocalories of energy in the body. The same amount of brown fat could burn up to 300 kilocalories a day.
There has been a lot of excitement surrounding the discovery of irisin because the energy-burning nature of brown fat makes it a potential therapeutic tool for targeting obesity and diabetes. It appears to be a golden ticket to promoting a healthy metabolism: as well as burning calories, it drains the blood of glucose (useful for preventing the onset of type II diabetes) as well as draining blood of unhealthy fat like triglycerides.
Also through studies in the laboratory on animals, FGF21 has been found to be a powerful activator of this brown fat, energy burning process. It is a molecule that originates in the liver and in brown fat itself. Since brown fat was discovered in humans, researchers have been bent on working out how to stimulate more of it, which makes this new research particularly exciting.
The capacity of brown fat to burn calories in order to produce heat and maintain body temperature in cold environments has long been known in animals. We are all born with supplies of brown fat; it is nature’s way of preventing hypothermia in babies. But until recently, it was thought to vanish in early infancy, getting replaced by “bad” white fat that sits on our waistlines.
We now know that brown fat is present in most, if not all, adults. Those with more brown fat are slimmer than those without. Glucose levels are also lower in humans with more brown fat. Efforts are therefore being made into understanding how brown fat is stimulated in humans. Previous studies have shown how irisin activates it in rodents; this research is an important step in understanding how it is stimulated in humans.
Stretchy, self-healing paints and other coatings recently took a step closer to common use, thanks to research being conducted at the University of Illinois. Scientists there have used "off-the-shelf" components to create a polymer that melds back together after being cut in half, without the addition of catalysts or other chemicals.
The material is made from a proprietary mixture of inexpensive commercially-available compounds, including a polyurea elastomer – polyurea is commonly found in a wide variety of products such as paints and plastics. The researchers reportedly "tweaked" the structure of its molecules, making the bonds between them longer. As a result, the molecules are easier to pull apart from one another, but they're also better able to bond back together.
When samples of what is being called "dynamic polyurea" are cut and then left for a day with the severed ends touching, they will heal back together with almost the same strength that they had before cutting. The process works at room temperature, although raising the ambient temperature to 37ºC (98.6ºF) will speed it up.
Some other experimental self-healing materials incorporate liquid-filled micro-capsules that break open when the material is cut or cracked. This means that they will only heal as long as there are unruptured capsules present. By contrast, dynamic polyurea can reportedly heal over and over again, as it relies solely on its molecular structure.
During development, the nervous system forms as a flat sheet called the neuroepithelium on the outer layer of the embryo. This sheet eventually folds in on itself to form a neural tube that gives rise to the brain and spinal cord—a process that involves the proliferation and migration of immature nerve cells to form the brain at one end and the spinal cord at the other. Yoshiki Sasai, Taisuke Kadoshima and colleagues from the RIKEN Center for Developmental Biology have now shown that human embryonic stem (ES) cells can spontaneously organize into the cerebral cortical tissue that forms at the front, or ‘brain’ end, of the developing neural tube.
Sasai and his colleagues previously developed a novel cell culture technique that involves growing ES cells in suspension, and have shown that these cells can self-organize into complex three-dimensional structures. They have already used this method to grow pieces of cerebral cortex and embryonic eyes from mouse ES cells. And more recently, they have shown that human ES cells can also organize into embryonic eyes containing retinal tissue and light-sensitive cells.
In their most recent work, Sasai’s team treated human ES cells grown using their cell culture system with signaling molecules that induce the formation of nervous tissue from the outer embryonic layer. They found that the cells spontaneously organize into neuroepithelial tissue that then folds up to give a multilayered cortex (see above figure).
During human embryonic development, the neural tube thickens at both ends. In particular, the front end thickens dramatically as waves of cells migrate outward to form the layered cerebral cortex and other parts of the brain. An important finding of the team’s is that the front end of the neural tube appears to thicken due to the growth of radial glial fibers, which span the thickness of the tube and guide migrating cells, rather than due to the accumulation of immature cells within the tube, as previously thought.
The findings also highlight critical differences between the development of the neural tube in mice and humans. While in humans, the inner surface of the neural tube and the intermediate neuroepithelial zone underneath it contain distinct populations of neural progenitors resembling radial glia, the progenitor population in the latter is not present in the developing mouse cortex.
“Efficient generation of cortical tissues could provide a valuable resource of functional neurons and tissues for medical applications,” says Kadoshima. “By combining this method with disease-specific human induced pluripotent stem cells, it will also be possible to reproduce complex human disorders.”
The Netherlands' population of wild fire salamanders (Salamandra salamandra; pictured) declined by 96% in the past three years, but no known infectious agent was found on their bodies. Now An Martel at Ghent University in Merelbeke, Belgium, and her team identify the problem as a new species of chytrid fungus, Batrachochytrium salamandrivorans. Healthy salamanders that were experimentally infected with the fungus developed skin lesions and died.
Unlike the only other chytrid fungus known to cause deadly infections (B. dendrobatidis, which has ravaged global frog and toad populations), this new species does not affect midwife toads (Alytes obstetricans). It also grows at much lower temperatures, suggesting that the two chytrid species occupy different niches. The researchers developed a DNA-testing method to rapidly screen salamanders for the fungus, with the aim of tracking this latest threat to biodiversity.
Emerging infectious diseases threaten all forms of life on Earth. Many pathogens of great historical and contemporary significance have originated from other species, triggering pandemics, disrupting agriculture, and challenging efforts to conserve endangered wildlife. Despite decades of research on species-jumping pathogens, the most central questions in the field remain major stumbling blocks for societies that seek to mitigate their impacts. These questions include which pathogens are most likely to emerge, which hosts are most likely to share pathogens, and what will be the long-term fate of newly emerged pathogens? Part of the challenge is that emergence, by nature, transcends scientific disciplines, occurring as the product of human behavior, environmental change, population, cellular and molecular biology, and evolution. Solutions therefore demand innovative pairing of theory and fundamental science with applied research and evidence-based policy-making.
Wounded leaves communicate their damage status to one another through a poorly understood process of long-distance signalling. This stimulates the distal production of jasmonates, potent regulators of defence responses.
One Green Planet See the Great Bear Rainforest Like You've Never Seen It Before (VIDEO) One Green Planet According to the organization's crowdfunding page, Great Bear LIVE is “an innovative research project and conservation tool that transmits live...
Actinomycetes are known for their unprecedented ability to produce novel lead compounds of clinical and pharmaceutical importance. This review focuses on the diversity, abundance and methodological approaches targeting marine sponge-associated actinomycetes. Additionally, novel qPCR data on actinomycete abundances in different sponge species and other environmental sources are presented. The natural products literature is covered, and we are here reporting on their chemical structures, their biological activities, as well as the source organisms from which they were isolated.
Usama Ramadan Abdelmohsen,*ab Kristina Bayera and Ute Hentschela Show AffiliationsNat. Prod. Rep., 2014, Advance Article
Spinach looks nothing like parsley, and basil bears no resemblance to thyme. Each plant has a typical leaf shape that can differ even within the same family. The information about what shape leaves will be is stored in the DNA. According to researchers at the Max Planck Institute for Plant Breeding Research in Cologne, the hairy bittercress (Cardamine hirsuta) has a particular gene to thank for its dissected leaves. This homeobox gene inhibits cell proliferation and growth between leaflets, allowing them to separate from each other. The thale cress Arabidopsis thaliana does not have this gene. Therefore, its leaves are not dissected, but simple and entire.
Miltos Tsiantis and his colleagues at the Max Planck Institute for Plant Breeding Research in Cologne discovered the new gene when comparing two plants from the Brassicaceae family: Cardamine hirsuta has dissected leaves that form leaflets and Arabidopsis thaliana has simple leaves. The researchers identified the RCO (REDUCED COMPLEXITY) gene, which makes leaves of the hairy bittercress more complex. Arabidopsis lacks this gene and, accordingly, lacks leaflets. RCO is only active in growing leaves. RCO ensures that cell proliferation and growth is prevented in areas of the leaf margin between sites of leaflet formation. “The leaves of Arabidopsis are simple and entire because growth is not inhibited by the RCO gene,” explains Tsiantis. “If we had not compared the two plants we would never have discovered this difference, as it is impossible to find a gene where none exists,” he adds.
The scientists first identified the RCO gene through a mutation in the hairy bittercress. In the absence of functional RCO the hairy bittercress can no longer produces leaflets. The RCO gene belongs to a cluster of three genes, which arose during evolution through the duplication of a single gene. In the thale cress, the original triple cluster now consists of a single gene. When the scientists return the RCO gene to the thale cress in the laboratory, evolution is partially reversed. “The simple oval leaves of Arabidopsis now develop deep lobes” says Tsiantis, “The fact that the leaf shape becomes complex again through the transfer of the RCO gene alone, shows that most of the apparatus for the formation of leaflets must still be present in the thale cress and was not lost with the RCO gene.”
The research team also examined theRCO sequence in greater detail and found it is a Homeobox gene. These genes function like genetic switches in that they activate or deactivate other genes. The scientists also demonstrated that RCO function is restricted to leaf shape; it does not decide whether leaves actually form. The loss of theRCO gene does not give rise to any other visible changes in the hairy bittercress. Therefore, its effect is limited to the inhibition of growth on the leaf margin. RCO does not work with the plant hormone auxin here. This specificity makes RCO a more likely driver of leaf shape evolution than any other genes identified to date. Tsiantis and his colleagues aim to decode its exact functionality in the months to come.
A series of fossil discoveries in the 1990s changed our understanding of the lives of early birds and mammals, as well as the dinosaurs they shared an ecosystem with. All those discoveries had one thing in common: they came from a small region in northern China that preserved what is now called the Jehol Biota.
Until now, however, no one knew why so many well-preserved fossils were found in that region. In a new study published in Nature Communications, researchers discovered that this remarkable preservation might have been the result of a Pompeii-like event, where hot ash from a volcanic eruption entombed these animals.
According to Leicester University's Sarah Gabbott (who wasn’t involved in the study), “Unravelling the environments in which fossilization took place, as the authors do in this paper, is very important. It places the fossils within the context of their habitat and it allows us to determine what filters and biases may have played a part.” These biases may affect which organisms get preserved.
The fossils of the Jehol Biota are from the Early Cretaceous period, about 130 million years ago, and they comprise a wide variety of animals and plants. So far, about 60 species of plants, 1,000 species of invertebrates, and 140 species of vertebrates have been found in the Jehol Biota.
One of the most remarkable discoveries to arise from these fossils came in 2010, when Michael Benton of the University of Bristol found colour-banding preserved in dinosaur fossils. These stripes of light and dark are similar to stripes in modern birds, and they provided further evidence that dinosaurs evolved into birds. Benton also found that these fossils had intact mealnosomes—organelles that make pigments. This discovery allowed paleontologists to tell the colors of dinosaurs' feathers for the first time.
The area that supported the Jehol Biota is suspected to have been a wetland with many lakes. Most fossils are found in lakebeds, suggesting that either the fossils were washed into these lakes by floods or that the animals were in the lakes before fossilization took place.
Baoyu believes that if fossils don't separate bone joints, it means the animals must have been in the lake before dying. But that is not a convincing argument, Gabbott said. "A freshly dead carcass, buoyed by decay gases which collect in the stomach, can be transported for tens if not hundreds of kilometers without such disarticulation."
No other fossil location, let alone that which produced so many well-preserved samples, has ever been suggested to have undergone a similar event. However, a comparison can be made to what happened in Pompeii in 79 AD when Mount Vesuvius erupted. The ensuing destruction led to the preservation of the city’s architecture and objects but not of people or animals. The human and animal remains we see from Pompeii are plaster casts of the empty spaces their decomposed bodies left in the ash.
Diverse animals detect the Earth's magnetic field and use it as a cue in orientation and navigation. Most research on magnetoreception has focused on the directional or `compass' information that can be extracted from the Earth's field. Because the field varies predictably across the surface of the globe, however, it also provides a potential source of positional or `map' information, which some animals use to steer themselves along migratory pathways or to navigate toward specific target areas. The use of magnetic positional information has been demonstrated in several diverse animals including sea turtles, spiny lobsters, newts and birds, suggesting that such systems are phylogenetically widespread and can function over a wide range of spatial scales. These `magnetic maps' have not yet been fully characterized. They may be organized in several fundamentally different ways, some of which bear little resemblance to human maps, and they may also be used in conjunction with unconventional navigational strategies.
Salmons, for example, use Earth’s magnetic field to create a large-scale mental map which they follow to find suitable feeding grounds, a study published today in Current Biology has found. The salmons are born in rivers and live out the early part of their lives in freshwater before travelling hundreds or thousands of kilometres out into the open ocean, where they spend most of their adulthood.
It has long been suspected that salmon use Earth’s magnetic field to navigate during this long migration. But until now, the way that young salmon swim from their streambed out into the open ocean with no previous knowledge of the sea, nor any parents or experienced fish to follow, has been a mystery. Previous work has suggested they might be guided, in part, by taking cues from regional magnetic ﬁelds to determine the best course – termed the “inherited magnetic map”. Because this map is inherited the salmon do not require any previous knowledge of their migration path or location.
The idea of an inherited magnetic map has long been speculated, but until now there has been no empirical evidence to suggest that salmon can determine their geographic position using the geomagnetic field. Nathan Putman from Oregon State University has now shown that salmon do navigate using an inherited magnetic map.
Dr. Putman and colleagues tested young Chinook salmon against different magnetic fields, either north or south of their typical ocean range, and found that the fish orientate themselves back towards their home range. If a fish was exposed to a north magnetic field, for instance, it would change its swimming direction back south.
Putman and colleagues also examined magnetic field components (magnetic intensity and the inclination angle) to determine which feature the fish use as a cue and found that neither of the features alone elicited the complete turn-around response, indicating that salmon rely on a combination of the two.
The results of the study also suggest this trait is inherited, as salmon are able to navigate without requiring any previous learning.
An Oregon startup has developed a pocket-size device that uses tiny sponges to stop bleeding fast.
When a soldier is shot on the battlefield, the emergency treatment can seem as brutal as the injury itself. A medic must pack gauze directly into the wound cavity, sometimes as deep as 5 inches into the body, to stop bleeding from an artery. It’s an agonizing process that doesn't always work--if bleeding hasn't stopped after three minutes of applying direct pressure, the medic must pull out all the gauze and start over again. It’s so painful, “you take the guy’s gun away first,” says former U.S. Army Special Operations medic John Steinbaugh.
Even with this emergency treatment, many soldiers still bleed to death; hemorrhage is a leading cause of death on the battlefield. "Gauze bandages just don't work for anything serious," says Steinbaugh, who tended to injured soldiers during more than a dozen deployments to Iraq and Afghanistan. When Steinbaugh retired in April 2012 after a head injury, he joined an Oregon-based startup called RevMedx, a small group of veterans, scientists, and engineers who were working on a better way to stop bleeding.
RevMedx recently asked the FDA to approve a pocket-size invention: a modified syringe that injects specially coated sponges into wounds. Called XStat, the device could boost survival and spare injured soldiers from additional pain by plugging wounds faster and more efficiently than gauze.
The team’s early efforts were inspired by Fix-a-Flat foam for repairing tires. “That’s what we pictured as the perfect solution: something you could spray in, it would expand, and bleeding stops,” says Steinbaugh. “But we found that blood pressure is so high, blood would wash the foam right out.”
So the team tried a new idea: sponges. They bought some ordinary sponges from a hardware store and cut them into 1-centimeter circles, a size and shape they chose on a whim but later would discover were ideal for filling wounds. Then, they injected the bits of sponge into an animal injury. “The bleeding stopped,” says Steinbaugh. “Our eyes lit up. We knew we were onto something.” After seeing early prototypes, the U.S. Army gave the team $5 million to develop a finished product.
Why we age is a tricky evolutionary question. A full set of DNA resides in each of our cells, after all, allowing most of them to replicate again and again and again.
In our youth we are strong and healthy and then we weaken and die - that's probably how most would describe what aging is all about. But, in nature, the phenomenon of aging shows an unexpected diversity of patterns and is altogether rather strange, conclude researchers from The University of Southern Denmark.
Not all species weaken and become more likely to die as they age. Some species get stronger and less likely to die with age, while others are not affected by age at all. Increasing weakness with age is not a law of nature.
Researchers from the University of Southern Denmark have studied aging in 46 very different species including mammals, plants, fungi and algae, and they surprisingly find that there is a huge diversity in how different organisms age. Some become weaker with age – this applies to e.g. humans, other mammals, and birds; others become stronger with age – this applies to e.g. tortoises and certain trees, and others become neither weaker nor stronger – this applies to e.g. Hydra, a freshwater polyp.
"Many people, including scientists, tend to think that aging is inevitable and occurs in all organisms on Earth as it does for humans: that every species becomes weaker with age and more likely to die. But that is not the case", says evolutionary biologist and assistant professor Owen Jones from the Max-Planck Odense Center at the University of Southern Denmark .
He is the lead author of an article on the subject in the scientific journal Nature. Other authors are from the Max Planck Institute for Demographic Research in Rostock, Germany, the University of Queensland in Australia, University of Amsterdam in Holland and elsewhere.
Owen Jones and his colleagues studied aging in species ranging from oak trees, nematodes, baboons and lice to seaweed and lions. The species included 11 mammals, 12 other vertebrates, 10 invertebrates, 12 plants and one algae.
"The diversity of mortality and fertility patterns in these organisms surprised us, and there is clearly a need for more research before we fully understand the evolutionary causes of aging and become better able to address problems of aging in humans", says Owen Jones.
He points out that while there is plenty of scientific data on aging in mammals and birds, there is only sparse and incomplete data on aging in other groups of vertebrates, and most invertebrates, plants, algae, and fungi.
For several species mortality increases with age - as expected by evolutionary scientists. This pattern is seen in most mammal species including humans and killer whales, but also in invertebrates like water fleas. However, other species experience a decrease in mortality as they age, and in some cases mortality drops all the way up to death. This applies to species like the desert tortoise (Gopherus agassizii) which experiences the highest mortality early on in life and a steadily declining mortality as it ages. Many plant species, e.g. the white mangrove tree (Avicennia marina) follow the same pattern.
Amazingly, there are also species that have constant mortality and remain unaffected by the ageing process. This is most striking in the freshwater polyp Hydra magnipapillata which has constant low mortality. In fact, in lab conditions, it has such a low risk of dying at any time in its life that it is effectively immortal.
"Extrapolation from laboratory data show that even after 1400 years five per cent of a hydra population kept in these conditions would still be alive", says Owen Jones.
Several animal and plant species show remarkably little change in mortality throughout their life course. For example, these include rhododendron (Rhododendron maximum), great tit (Parus major), hermit crab (Pagurus longicarpus), common lizard (Lacerta vivapara), collared flycatcher (Ficedula albicollis), viburnum plants (Viburnum furcatum ), oarweed (Laminaria digitata), red abalone (Haliotis rufescens), the plant armed saltbush (Atriplex acanthocarpa), red-legged frog (Rana aurora) and the coral red gorgonian (Paramuricea clavata).
When you look at the fertility patterns of the 46 surveyed species, there is also a great diversity and some large departures from the common beliefs about ageing. Human fertility is characterized by being concentrated in a relatively short period of life, and by the fact that humans live for a rather long time both before and after the fertile period.
A similar pattern of a concentrated fertile period is also seen in other mammals like killer whales, chimpanzees, and chamois (Rupicapra rupicapra), and also in birds like sparrow hawks (Accipiter nisus).
However, there are also species that become more and more fertile with age, and this pattern is especially common in plants such as the agave (Agave marmorata) and the rare mountain plants hypericum (Hypericum cumulicola) and borderea (Borderea pyrenaica).
On the contrary fertility occurs very early in the nematode worm Caenorhabditis elegans. Actually this species starts its life with being fertile, then it quite quickly and quite suddenly loses the ability to produce offspring.
To sum up there is no strong correlation between the patterns of ageing and the typical life spans of the species. Species can have increasing mortality and still live a long time, or have declining mortality and still live a short time. "It makes no sense to consider ageing to be based on how old a species can become. Instead, it is more interesting to define ageing as being based on the shape of mortality trajectories: whether rates increase, decrease or remain constant with age", says Owen Jones.
Trees and forests provide a wide variety of ecosystem services in addition to timber, food, and other provisioning services. New approaches to pest and disease management are needed that take into account these multiple services and the different stakeholders they benefit, as well as the likelihood of greater threats in the future resulting from globalization and climate change. These considerations will affect priorities for both basic and applied research and how trade and phytosanitary regulations are formulated.
Human activity has been shown to considerably affect the spread of dangerous pests and pathogens worldwide. Therefore, strict regulations of international trade exist for particularly harmful pathogenic organisms. Phytophthora plurivora, which is not subject to regulations, is a plant pathogen frequently found on a broad range of host species, both in natural and artificial environments. It is supposed to be native to Europe while resident populations are also present in the US. We characterized a hierarchical sample of isolates from Europe and the US and conducted coalescent-, migration, and population genetic analysis of sequence and microsatellite data, to determine the pathways of spread and the demographic history of this pathogen. We found P. plurivora populations to be moderately diverse but not geographically structured. High levels of gene flow were observed within Europe and unidirectional from Europe to the US. Coalescent analyses revealed a signal of a recent expansion of the global P. plurivora population. Our study shows that P. plurivora has most likely been spread around the world by nursery trade of diseased plant material. In particular, P. plurivora was introduced into the US from Europe. International trade has allowed the pathogen to colonize new environments and/or hosts, resulting in population growth.