“Soil microbes are beneficial, and we couldn’t live without their cycling of carbon and nutrients, but climate change and drought can tweak that balance, and we have to be aware of how it’s changing,” says Allison of the University of California, Irvine.

Some soil microbes take carbon from decomposing plants and store it in the soil, while others release plant carbon back into the atmosphere. The carbon that ends up in the soil is beneficial in multiple ways. “The carbon in the soil has these reverberating effects out to the rest of the world in terms of the infrastructure in our natural and managed ecosystems,” says Allison. “Carbon-rich soils hold more nutrients, so plants growing in those soils tend to be more productive, and the carbon changes the physical properties of the soil, which prevents erosion.”

“In California now, we have this system where the droughts are more intense, and then the rainfall is more intense,” he says. “So, if you’re losing your soil carbon, when it rains really hard it could carry away your soil and cause erosion, landslides, mudslides, sediments, and all kinds of problems that we’re actually seeing right now.”

The carbon that is released back into the atmosphere is another story. “From a climate mitigation standpoint, what we want is for more carbon to be in plants and soils and less carbon to be in the atmosphere, so the more carbon we can absorb into plants through photosynthesis and the more we can transfer and keep in the soil, the better off we’re going to be in terms of climate change,” says Allison. “That’s why it’s really important to know how the balance of incoming versus outflowing carbon changes with drought, or warming, or any other climate factor.”

Plants and microbes will both be impacted by the increasing frequency of drought, but Allison suspects that microbes will be able to bounce back faster. “Microbes are really adaptable — they can change their physiology, they can change their abundances so that more drought-adapted microbes take over, and they can potentially evolve — so we expect that they are going to resist or bounce back from drought,” says Allison. “All those different processes can happen pretty quickly with microbes, and much more quickly than with plants.”

If more carbon-releasing microbes survive than carbon-sequestering microbes, we could end up with carbon-depleted soils, which would have serious negative implications for plant productivity and future greenhouse gas levels.

We may be able to nudge the balance in the right direction, Allison says, but more research is needed first. “There’s still a lot to be done. Right now, we have data that suggests that when we have drought, something changes that results in carbon loss, but we don’t understand exactly how or why that’s happening, whether drought’s changing the abundance of beneficial plant associated microbes versus the carbon releasing microbes, or if it’s causing the evolution of one of the microbe groups, or if it’s more determined by changes to their immediate physiology,” says Allison.

Some microbes could actually help plants cope with drought. If we knew which microbes were most beneficial to plants, and most likely to retain carbon in soil, we could try to tip the balance in their favor.

“There’s a lot of potential for us to manage or engineer soil microbes,” says Allison. “In agricultural systems, we can look into manipulating the soil or adding beneficial microbes back in. In more natural systems, management would probably be on the plant side: soil microbes are often closely intertwined with plants, so managing the plants can also benefit the microbial part of the ecosystem.”

“We also need more measurements to get a good sense of how drought affects soil carbon change in different ecosystems,” says Allison. “There’s a lot of landscape out there — from the Arctic tundra to the deserts — and we could use more research across those diverse habitats.”

Materials that strongly change their resistivity under magnetic fields are highly sought for various applications and, for example, every car and every computer contain many tiny magnetic sensors. Such materials are rare, and most metals and semiconductors change their electrical resistivity only by a tiny fraction of a percent at room temperature and in practically viable magnetic fields (typically, by less than a millionth of 1 %). To observe a strong magnetoresistance response, researchers usually cool materials to liquid-helium temperatures so that electrons inside scatter less and can follow cyclotron trajectories.

Now a research team led by Professor Sir Andre Geim has found that good old graphene that seemed to be studied in every detail over the last two decade exhibits a remarkably strong response, reaching above 100% in magnetic fields of standard permanent magnets (of about 1,000 Gauss). This is a record magnetoresistivity among all the known materials.

Speaking about this latest graphene discovery, Sir Andre Geim said: “People working on graphene like myself always felt that this gold mine of physics should have been exhausted long ago. The material continuously proves us wrong finding yet another incarnation. Today I have to admit again that graphene is dead, long live graphene.”

To achieve this, the researchers used high-quality graphene and tuned it to its intrinsic, virgin state where there were only charge carriers excited by temperature. This created a plasma of fast-moving “Dirac fermions” that exhibited a surprisingly high mobility despite frequent scattering. Both high mobility and neutrality of this Dirac plasma are crucial components for the reported giant magnetoresistance.

“Over the last 10 years, electronic quality of graphene devices has improved dramatically, and everyone seems to focus on finding new phenomena at low, liquid-helium temperatures, ignoring what happens under ambient conditions. This is perhaps not so surprising because the cooler your sample the more interesting its behaviour usually becomes. We decided to turn the heat up and unexpectedly a whole wealth of unexpected phenomena turned up,” says Dr Alexey Berdyugin, the corresponding authors of the paper.

In addition to the record magnetoresistivity, the researchers have also found that, at elevated temperatures, neutral graphene becomes a so-called “strange metal.” This is the name given to materials where electron scattering becomes ultimately fast, being determined only by the Heisenberg uncertainty principle. The behaviour of strange metals is poorly understood and remains a mystery currently under investigation worldwide.

The Manchester work adds some more mystery to the field by showing that graphene exhibits a giant linear magnetoresistance in fields above a few Tesla, which is weakly temperature dependent. This high-field magnetoresistance is again record-breaking.

The phenomenon of linear magnetoresistance has remained an enigma for more than a century since it was first observed. The current Manchester work provides important clues about origins of the strange metal behaviour and of the linear magnetoresistance. Perhaps, the mysteries can now be finally solved thanks to graphene as it represents a clean, well-characterised and relatively simple electronic system.

“Undoped high-quality graphene at room temperature offers an opportunity to explore an entirely new regime that in principle could be discovered even a decade ago but somehow was overlooked by everyone. We plan to study this strange-metal regime and, surely, more of interesting results, phenomena and applications will follow,” adds Dr Leonid Ponomarenko, one of the leading Nature paper authors.

Scientists at Max Delbrück Center in Berlin, the Andalusian Center for Developmental Biology (CABD) in Seville and other labs in the United States have discovered how the skate evolved these cape-like fins by peering into their DNA. They found that the key to the evolution of the skate fins lies not in the coding regions of its genome, but rather in the non-coding bits and the three-dimensional complexes that it folds into. These 3D structures are called “topologically associated domains” (TADs).

The international team describes in Nature that genomic changes that alter TADs can drive evolution. Until recently, genome evolution was mostly focused on studying variation at the DNA sequence level, but not in 3D genomic structures. “This is a new way of thinking about how genomes evolve,” says Dr. Darío Lupiáñez, geneticist at the Max Delbrück Center and one of the lead authors of the study.

“Although we found that unique gene-expression patterns establish exceptionally wide skate fins a while ago, the underlying regulatory changes in the genome have previously remained unknown,” says co-author Dr. Tetsuya Nakamura, developmental biologist at Rutgers University.

More than 450 million years ago, the genome of a primitive fish — the ancestor of all vertebrate animals — duplicated twice. The expansion in genetic material drove the rapid evolution of more than 60,000 vertebrates, including humans. One of our most distant vertebrate relativesare little skates (Leucoraja erinacea), which belong to a lineage of cartilaginous fishes that includes sharks and rays. These distant cousins are ideal organisms to learn about the evolution of traits that made us human, such as paired appendages. “Skates are cartilaginous fishes called Chondrichthyans. They are considered more similar to ancestral vertebrates,” says Dr. Christina Paliou, a developmental biologist at the CABD and one of the first authors. “We can compare the characteristics of skates with other species and determine what is novel and what is ancestral.”

An exciting time in evolutionary genomics

In 2017, the late Dr. José Luis Gómez-Skarmeta from the CABD, a founding figure in evolutionary genomics, brought together scientists from around the world to study skate evolution: laboratories with expertise in genome evolution such as the Ferdinand Marlétaz lab at University College London and Daniel Rokhsar lab at the University of California-Berkeley, in skate biology such as the Neil Shubin lab at University of Chicago, where Tetsuya Nakamura was then located (now at Rutgers) and in 3D gene regulation such as the Juan Tena at CABD, Darío Lupiáñez and Gómez-Skarmeta labs, as well as other collaborators. Gómez-Skarmeta was interested in learning how genomes evolve structurally and functionally to promote the appearance of new traits. “To a great extent, evolution is the history of changing the regulation of gene expression during development,” he said in 2018.

It was an exciting time for evolutionary genomics. Genome sequencing technologies had significantly improved and scientists could gain novel insights into how DNA, which stretches a couple of meters end-to-end, is folded into a 0.002-inch-diameter cell nucleus. “The packaging of DNA in the nucleus is far from random,” says Lupiáñez. The DNA folds into 3D structures called TADs, which contain genes and their regulatory sequences. These 3D structures ensure that the appropriate genes are switched on and off at the right time, in the right cells.

Dr. Rafael Acemel, a geneticist at the Max Delbrück Center and one of the first authors, performed experiments using the Hi-C technology, to elucidate the 3D structure of the TADs. But interpreting the results was challenging at first as the scientists needed the complete skate genome as a reference point. “At the time, the reference consisted of thousands of small unordered pieces of DNA sequence, so that did not help,” Acamel says.

To overcome this difficulty, the scientists used long-read sequencing technology, together with Hi-C data, to assemble the pieces of the DNA like a puzzle and assign the unordered sequences to skate chromosomes. With the new reference, assembling the 3D structure of the TADs using Hi-C became trivial.

They compared this improved skate genome with genomes of the closest relatives, sharks, to identify any TADs altered during skate evolution. These altered TADs included genes of the Wnt/PCP pathway, which is important for the development of fins. There was also a skate-specific variation in a non-coding sequence near the Hox genes, which also regulate fin development. “This specific sequence can activate several Hox genes in the front part of the fins, which does not happen in other fish or four-legged animals,” says Paliou. Subsequently, the scientists performed functional experiments that confirmed these molecular changes helped the skates evolve their unique fins.

TADs drive evolution

Earlier research has shown that changes in TADs can affect the expression of genes and cause diseases in humans. In this study, scientists show a role for TADs in driving evolution that has been previously noted for moles, too.

After the primitive fish ancestor duplicated its genome, many unused and redundant parts were subsequently lost. “It was not only the genes that disappeared, but also the associated regulatory elements and the TADs they are contained in,” Lupiáñez says. “I think it’s an exciting finding as it suggests that the 3D structure of the genome has an influence on its evolution.”

TADs are important for gene regulation, 40 percent of them are conserved in all vertebrates, Acemel says. “However, 60 percent of TADs have evolved in some way or another. What were the consequences of these changes for species evolution? I think that we are just scratching the surface of this exciting phenomenon,” Acemel says.

This mechanism of evolution constrained by TADs could be prevalent in nature. “We suspect that these mechanisms might explain many other interesting phenotypes that we observe in nature,” Lupiáñez says. “By adding these new layers of gene expression, gene regulation, and 3D chromatin organization, the field of evolutionary genomics is entering into a new era of discovery.”