Perceiving Predators: Understanding How Plants “Sense” Herbivore Attack (Botany)

How “elicitors” can initiate defense responses in plants against herbivores, and can potentially lead to development of pesticide-free agriculture

Plants are known to possess solid immune response mechanisms. One such response is “sensing” attack by herbivorous animals. In a new review article, Prof. Arimura from Tokyo University of Science, Japan, discusses “elicitors”-the molecules that initiate plant defense mechanisms against herbivore attack. He highlights the major types of elicitors and the underlying cellular signaling, and states that this could spur research on organic farming practices that could prevent the use of harmful pesticides.

Nature has its way of maintaining balance. This statement rightly holds true for plants that are eaten by herbivores-insects or even mammals. Interestingly, these plants do not just silently allow themselves to be consumed and destroyed; in fact, they have evolved a defense system to warn them of predator attacks and potentially even ward them off. The defense systems arise as a result of inner and outer cellular signaling in the plants, as well as ecological cues. Plants have developed several ways of sensing damage; a lot of these involve the sensing of various “elicitor” molecules produced by either the predator or the plants themselves and initiation of an “SOS signal” of sorts.

In a recently published review in the journal Trends in Plant Science, Professor Gen-ichiro Arimura from Tokyo University of Science, Japan, encapsulates the research on the herbivory-sensing mechanism of plants through elicitors,. Commenting of the immense value of these elicitors, Prof. Arimura states, “This review focuses mainly on elicitors because they are timely, novel, and have potential biotechnological applications”.

When the same herbivorous animal comes to eat the plant multiple times, the plant learns to recognize its feeding behavior and records the “molecular pattern” associated with it. This is termed “herbivore-associated molecular patterns” or HAMPs. HAMPs are innate elicitors. Other plant elicitors include plant products present inside cells that leak out because of the damage caused by herbivory. Interestingly, when an herbivorous insect eats the plant, the digestion products of the plant cell walls and other cellular components become part of the oral secretions (OS) of the insect, which can also function as an elicitor!

Prof. Arimura highlights the fact that with the advancement of high-throughput gene- and protein-detecting systems, the characterization of elicitors of even specific and peculiar types of herbivores, such as those that suck cell sap and do not produce sufficient amounts of OS, has become possible. The proteins present in the salivary glands of such insects could be potential elicitors as they enter the plant during feeding. He explains, “RNA-seq and proteomic analyses of the salivary glands of sucking herbivores have led to the recent characterization of several elicitor proteins, including a mucin-like salivary protein and mite elicitor proteins, which serve as elicitors in the leaves of the host plants upon their secretion into plants during feeding.”

The review also highlights some peculiar elicitors like the eggs and pheromones of insects that plants can detect and initiate a defense response against. In some special cases, the symbiotic bacteria living inside the insect’s gut can also regulate the defense systems of the plants.

And now that we have understood different types of elicitors, the question remains-what signaling mechanisms do the plants use to communicate the SOS signal?

So far, it has been hypothesized that the signaling is made possible by proteins transported through the vascular tissue of plants. Interestingly, there is evidence of airborne signaling across plants, by a phenomenon called “talking plants.” Upon damage, plants release volatile chemicals into the air, which can be perceived by neighboring plants. There is also evidence of epigenetic regulation of defense systems wherein plants maintain a sort of “genetic memory” of the insects that have attacked them and can fine-tune the defense response accordingly for future attacks.

Given the improvement in knowledge of the mechanisms of plant defense systems, we can embrace the possibility of a “genetic” form of pest control that can help us circumvent the use of chemical pesticides, which, with all their risks, have become a sort of “necessary evil” for farmers. This could usher in modern, scientifically sound ways of organic farming that would free agricultural practices from harmful chemicals.


Reference

Title of original paper: Making Sense of the Way Plants Sense Paper: Herbivores Journal: Trends in Plant Science DOI:10.1016/j.tplants.2020.11.001


Provided by Tokyo University of Science

How Icebergs Really Melt — And What This Could Mean For Climate Change (Maths)

Icebergs are melting faster than current models describe, according to a new study by mathematicians at the University of Sydney. The researchers have proposed a new model to more accurately represent the melt speed of icebergs into oceans.

Their results, published in Physical Review Fluids, have implications for oceanographers and climate scientists.

Lead author and PhD student Eric Hester said: “While icebergs are only one part of the global climate system, our improved model provides us with a dial that we can tune to better capture the reality of Earth’s changing climate.”

Current models, which are incorporated into the methodology used by the Intergovernmental Panel on Climate Change, assume that icebergs melt uniformly in ocean currents. However, Mr Hester and colleagues have shown that icebergs do not melt uniformly and melt at different speeds depending on their shape.

“About 70 percent of the world’s freshwater is in the polar ice sheets and we know climate change is causing these ice sheets to shrink,” said Mr Hester, a doctoral student in the School of Mathematics & Statistics.

“Some of this ice loss is direct from the ice sheets, but about half of the overall ice loss from Greenland and Antarctica happens when icebergs melt in the ocean, so understanding this process is important.

“Our model shows that icebergs are melting at faster rates than current models assume,” he said.

As well as its importance for modelling how ice sheets are changing, Mr Hester said his research will help us better understand the impact of ice melt on ocean currents.

“Ocean circulation is the reason that Britain isn’t as cold as Alberta, Canada, despite being at similar latitudes,” Mr Hester said.

The Gulf Stream that takes warmer water from the tropics across the Atlantic keeps western Europe milder than it otherwise would be, he said.

“That current could shut down if too much freshwater is dumped into the system at once, so it’s critical we understand the process of iceberg and ice sheet melt.”

Eric Hester (right) and his PhD supervisor Dr Geoffrey Vasil from the School of Mathematics at the University of Sydney. © Louise Cooper/USYD

Where and when the freshwater is released, and how the ocean is affected, in part depends on the speed at which icebergs melt.

Co-author Dr Geoffrey Vasil from the University of Sydney said: “Previous work incorporating icebergs in climate simulations used very simple melting models. We wanted to see how accurate those were and whether we could improve on them.”

Mr Hester said their models – confirmed in experiment – and the observations of oceanographers show that the sides of icebergs melt about twice as fast as their base. For icebergs that are moving in the ocean, melting at the front can be three or four times faster than what the old models predicted.

“The old models assumed that stationary icebergs didn’t melt at all, whereas our experiments show melting of about a millimetre every minute,” Mr Hester said.

“In icebergs moving in oceans, the melting on the base can be up to 30 percent faster than in old models.”

The research shows that iceberg shape is important. Given that the sides melt faster, wide icebergs melt more slowly but smaller, narrower icebergs melt faster.

“Our paper proposes a very simple model that accounts for iceberg shape, as a prototype for an improved model of iceberg melting,” Dr Vasil said.

To test these models, the researchers developed the first realistic small-scale simulations of melting ice in salt water.

“We are confident this modelling captures enough of the complexity so that we now have a much better way to explain how icebergs melt,” Mr Hester said.

Dr Vasil, who is Mr Hester’s PhD supervisor, said: “Before Eric started his PhD the computational tools to model these kinds of systems didn’t really exist.

“Eric took a very simple prototype and made it work wonderfully on the complex ice-melting problem.”

Dr Vasil said that these methods can be applied to many other systems, including glaciers melting or the melting of frozen, saline sea ice.

“But it doesn’t end there. His methods could also be used by astrobiologists to better understand ice moons like Saturn’s Enceladus, a candidate for finding life elsewhere in the Solar System.”

The research was done in collaboration with scientists from the British Antarctic SurveyUniversity of Canterbury in New Zealand and the Woods Hole Oceanographic Institution in Massachusetts, USA.

Eric Hester was partially funded by the US National Science Foundation (NSF) for his fellowship at the Woods Hole Oceanographic Institution and by the William and Catherine McIlarth Travel Scholarship at the University of Sydney. Other researchers received partial funding from the EU Horizon program and the NSF. The researchers acknowledge access to the PRACE supercomputer at CINECA, Italy.

DOWNLOAD a video of the experiment, the academic paper and photos at this link.

EMBED a YouTube video explainer (30 seconds) at this link.

READ an article about the research by the American Physical Society at this link.


Reference: Eric W. Hester, Craig D. McConnochie, Claudia Cenedese, Louis-Alexandre Couston, and Geoffrey Vasil, “Aspect ratio affects iceberg melting”, Phys. Rev. Fluids 6, 023802 – Published 12 February 2021. https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.6.023802


Provided by University of Sydney

3D Model Shows Off The Insides of a Giant Permafrost Crater (Geology)

Researchers from the Oil and Gas Research Institute of the Russian Academy of Sciences and their Skoltech colleagues have surveyed the newest known 30-meter deep gas blowout crater on the Yamal Peninsula, which formed in the summer of 2020. The paper was published in the journal Geosciences.

Giant craters in the Russian Arctic, thought to be the remnants of powerful gas blowouts, first attracted worldwide attention in 2014, when the 20 to 40-meter wide Yamal Crater was found quite close to the Bovanenkovo gas field. The prevailing hypothesis is that these craters are formed after gas is accumulated in cavities in the upper layers of permafrost, and increasing pressure ultimately unleashes an explosive force. Most of these craters are rather short-lived as they apparently quickly fill with water over several years and turn into small lakes. As of now, there are some 20 known and studied craters.

In 2020, researchers found and surveyed the latest crater, dubbed C17, about 25 meters in diameter. It was found by Andrey Umnikov, director of the non-profit partnership “Russian Center of Arctic Development,” during a helicopter flight on July 16 in the central part of the Yamal Peninsula, close to three other craters including the famous Yamal Crater. OGRI deputy director Vasily Bogoyavlensky led the August 2020 expedition, which was possible thanks to the generous support of the government of Yamalo-Nenets Autonomous Area and Mr Umnikov’s organization. Evgeny Chuvilin and Boris Bukhanov from the Skoltech Center for Hydrocarbon Recovery took part in the expedition.

“The new crater is impressive in its ideal state of preservation, primarily the cone-shaped top where ejecta was thrown from, the outer parts of the heaving mound that precipitated the crater, the walls of the crater itself which are incredibly well preserved, and, of course, the gas cavity in the icy bottom of the crater,” Chuvilin says.

“Firstly, we got there in time to find the object in its almost pristine state, with no water filling it. Secondly, the giant underground cavity in the ice is unique in itself. A part of the icy dome of this cavity was preserved; before the explosion, it had this circular dome, and its bottom was elliptical, elongated to the north, with its axis ratio of approximately 1 to 4.5. From what we know we can say that the C17 crater is linked to a deep fault and an anomalous terrestrial heat flow,” Bogoyavlensky notes.

A certified pilot, Igor Bogoyavlensky, piloted the drone used for crater surveillance. That was the first time a drone flew inside the crater for “underground aerial survey” 10 to 15 meters below ground, running the risk of losing the aircraft. The team used the data to build a 3D model based on the drone footage from inside the crater. This is the first time scientists were able to study a “fresh” crater that has not yet eroded or filled with water, with a well-preserved ice cavity where gas had been accumulating. 3D modeling was earlier used for the Yamal Crater, but at the time it was already filled with water.

“Over the years we’ve gained a lot of experience with surveillance drones, yet this “underground aerial survey” of the C17 crater was the most difficult task I had ever faced, having to lie down on the edge of a 10-story deep crater and dangle down my arms to control the drone. Three times we got close to losing it, but succeeded in getting the data for the 3D model,” Igor Bogoyavlensky, the drone pilot, says.

Vasily Bogoyavlensky says the 3D model allowed them to capture the extremely complex shape of the underground cavity. “We could not see everything from above, especially the grottos, possible caverns in the lower part of the crater. You can clearly see all that with the 3D model. Our results suggest unequivocally that the crater was formed endogenously, with ice melting, a heaving mound dynamically growing due to gas accumulation and the explosion,” he adds.

The Skoltech researchers were able to study the cryogeological conditions of the crater, the composition of permafrost in this area as well as ejecta from the crater, temperature conditions at the crater floor and some other parameters. “This information will shed light on the conditions and formation of these unusual objects in the Arctic,” Chuvilin points out. 

In 2021, OGRI and Skoltech researchers are planning a new expedition to this crater to monitor its state and conduct further research into how it was formed.

Featured image: C17 Crater © Evgeny Chuvilin


Reference: Bogoyavlensky, Vasily; Bogoyavlensky, Igor; Nikonov, Roman; Kargina, Tatiana; Chuvilin, Evgeny; Bukhanov, Boris; Umnikov, Andrey. 2021. “New Catastrophic Gas Blowout and Giant Crater on the Yamal Peninsula in 2020: Results of the Expedition and Data Processing” Geosciences 11, no. 2: 71. https://doi.org/10.3390/geosciences11020071


Provided by Skoltech

Sloshing Quantum Fluids of Light and Matter To Probe Superfluidity (Quantum)

The ‘sloshing’ of a quantum fluid comprised of light and matter reveals superfluid properties.

An Australian-led team of physicists have successfully created sloshing quantum liquids in a ‘bucket’ formed by containment lasers.

“These quantum fluids are expected to be as wavy as the oceans, but catching clear pictures of the waves is an experimental challenge,” says lead author Dr Eliezer Estrecho.

Led by the Australian National University (ANU), the team serendipitously observed the wavy motion of the quantum fluid in an optically-controlled bucket, gaining new insights of the intriguing superfluid properties of this peculiar, hybrid light-matter system.

A containment ‘bucket’ (in red) holds the light-matter condensate (blue) © Fleet

Superfluidity is the flow of particles without suffering resistance, and is pursued by FLEET researchers for future applications in ultra low-energy electronics.

FILLING THE BUCKET WITH THE QUANTUM FLUID LED TO SLOSHING

The team performed the experiments in a laser-made ‘bucket’ that traps particles called exciton-polaritons, which are hybrid light-matter particles in a semiconductor.

As these particles cool down they form a giant quantum object called a Bose-Einstein condensate (sometimes referred to as the fifth state of matter), in which quantum phenomena can be seen on a macroscopic scale.

The new study was led by FLEET Research Fellow Dr Eliezer Estrecho, at ANU (Credit: Phil Dooley, ANU)

“The excess energy lost by the cooling particles does not disappear easily so the condensate will display some sort of wavy behaviour, which is random for every realisation of the condensation,” says corresponding author Prof Elena Ostrovskaya.

That randomness makes it hard to detect the transient oscillations with the imaging cameras, since it will average out in the experiment.

However, fortuitously, the ‘bucket’ is tilted.

“In most experiments, we try to avoid the tilt since it complicates the analysis,” says Dr Estrecho.

“But in this case the ‘annoying’ tilt enabled the observation of the oscillation because  it is favourable for the condensate to slosh along the tilt direction.

Sloshing quantum fluid in position space (left) and momentum space (right). Slowed 100 million times. © Fleet

The sloshing oscillation was observed in both the position and momentum of the condensate, beautifully displaying the laws of quantum mechanics at a macroscopic scale that can be seen by an ordinary microscope. However, the oscillations are extremely fast, so that it was only possible to observe them using a camera with a picosecond-scale temporal resolution.

STUDYING THE SPEED OF SOUND IN SUPERFLUIDS

The true beauty of the experiment lies in the analysis of the oscillation frequencies since it is directly related to the speed of sound and can probe the superfluid properties of the quantum fluid. This is especially relevant since this peculiar quantum fluid can exist at room temperature, and hence is promising for device applications.

Using a clever analysis, the team has extracted the speed of sound from the experimental data, and found that it is smaller than expected from prevailing theories. The team argued that the discrepancy arises from the existence of an invisible reservoir of hot matter-like particles that interact with the hybrid light-matter particles.

Furthermore, the experiment also provides clues on the possible effects that can slow down the superfluid. At absolute zero temperature, the oscillations are expected to never end since the system is a superfluid. However, at finite temperature, this is not the case, so studying the damping rates of the oscillations is essential in understanding the superfluid.

Initial results show that neither the reservoir particles, finite temperature, or the inherent short lifetime of exciton-polaritons can solely explain the observed damping rates. Hence, further theoretical studies that combine these effects and carefully controlled experiments are needed to better understand the non-equilibrium quantum fluid.


THE STUDY

Low-energy collective oscillations and Bogoliubov sound in an exciton-polariton condensate was published as an Editor’s Suggestion in Physical Review Letters in February 2021. (DOI 10.1103/physrevlett.126.075301)


Provided by Fleet

Experimental Tests of Relativistic Chemistry Will Update the Periodic Table (Chemistry)

Researchers from Osaka University are better understanding the chemistry of superheavy elements, which will help explain important discrepancies in the periodic table and may eventually lead to the development of new materials

All chemistry students are taught about the periodic table, an organization of the elements that helps you identify and predict trends in their properties. For example, science fiction writers sometimes describe life based on the element silicon because it is in the same column in the periodic table as carbon.

However, there are deviations from expected periodic trends. For example, lead and tin are in the same column in the periodic table and thus should have similar properties. However, whilst lead-acid batteries are common in cars, tin-acid batteries don’t work. Nowadays we know that this is because most of the energy in lead-acid batteries is attributable to relativistic chemistry but such chemistry was unknown to the researchers who originally proposed the periodic table.

Relativistic chemistry is difficult to study in the superheavy elements, because such elements are generally produced one at a time in nuclear fission reactions and deteriorate quickly. Nevertheless, having the ability to study the chemistry of superheavy elements could uncover new applications for superheavy elements and for common lighter elements, such as lead and gold.

In a recent study in Nature Chemistry, researchers from Osaka University studied how single atoms of superheavy rutherfordium metal react with two classes of common bases. Such experiments will help researchers use relativistic principles to better utilize the chemistry of many elements.

“We prepared single atoms of rutherfordium at RIKEN accelerator research facility, and attempted to react these atoms with either hydroxide bases or amine bases,” explains Yoshitaka Kasamatsu, lead author on the study. “Radioactivity measurements indicated the end result.”

Schematic diagram of online co-precipitation experiment of 261Rf. © Osaka University

Researchers can better understand relativistic chemistry from such experiments. For example, rutherfordium forms precipitate compounds with hydroxide base at all concentrations of base, yet its homologues zirconium and hafnium in high concentrations. This difference in reactivity may be attributable to relativistic chemistry.

“If we had a way to produce a pure rutherfordium precipitate in larger quantities, we could move forward with proposing practical applications,” says senior author Atsushi Shinohara. “In the meantime, our studies will help researchers systematically explore the chemistry of superheavy elements.”

Relativistic chemistry explains why bulk gold metal is not silver-colored, as one would expect based on periodic table predictions. Such chemistry also explains why mercury metal is a liquid at room temperature, despite periodic table predictions. There may be many unforeseen applications that arise from learning about the chemistry of superheavy elements. These discoveries will depend on newly reported protocols and ongoing fundamental studies such as this one by Osaka University researchers.

The article, “Co-precipitation behaviour of single atoms of rutherfordium in basic solutions,” was published in Nature Chemistry at DOI: https://doi.org/10.1038/s41557-020-00634-6

Featured image: Brief overview of the present study © Osaka University


Provided by Osaka University

Plant As Superhero During Nuclear Power Plant Accidents (Botany)

In recent time, HBO’s highly acclaimed and award-winning miniseries Chernobyl highlighted the horror of nuclear power plant accident, which happened in Ukraine in 1986. It is not a fictional series just on TV. As we had seen such a catastrophic nuclear power plant accident in 2011 again caused by natural disaster, Tsunami, in Japan. Both historical nuclear power plant accidents released tons of radioactive cesium to the environment. Consequently, the radioactive cesium found their way to the surrounding land, river, into the plants and animal feed, and eventually to our food cycle and ecosystem. The more detrimental part is their half-life, as 137Cs has half-life of ~30 years. So, it is going to be a serious agricultural, economic, and health problem for such a long time without effective actions. Plant biologists use the technique call phytoremediation to use the plant or manipulate the plant genetically to take up toxic components from soil or make crop plants resilient to such contaminated soil. Over the years, scientists tried to find cesium transporters in plants, and till now mostly ended up with several potassium transporters. It is not surprising if someone thinks about the basic chemistry and periodic table of elements we learnt in the high school. Cesium (Cs) resides in the same group with potassium (K). But potassium is abundant in soil and important for plant growth and development. As a result, manipulating potassium transporter to regulate cesium uptake will cause problem for plant growth in general. In contrast to potassium, cesium is not abundant in the soil and it is toxic for plants. So, the idea of finding potassium-independent cesium transporter, which will transport cesium without affecting potassium, is a long waited one.

Recently, plant biologist Dr. Abidur Rahman’s group from Iwate University, Japan in a collaboration with Dr. Keitaro Tanoi from the University of Tokyo and Dr. Takashi Akihiro from the Shimane University reported two potassium-independent cesium transporters, where these two transporters dedicatedly uptake cesium inside the plant without affecting potassium. Their finding has been published recently in the top tier plant-specific journal from Cell press, Molecular Plant. They have shown that two ATP Binding Cassette (also known as ABC transporter in general and evolutionary abundant across the kingdom) proteins, ABCG33 and ABCG37, uptake cesium inside the cell.

“This study highlights how we can solve the agricultural issues around us with basic research and why the basic research should be funded”. This study also demonstrates the power of collaborations to answer the scientific questions” said the group leader Dr. Abidur Rahman.

“Arif Ashraf,one of the lead authors who conducted the study as part of his graduate study in the Iwate University and currently a postdoc at the University of Massachusetts Amherst, said that how the basic plant biology research can solve real-life problem around us” He added, “In this study, we combined plant physiology, molecular biology, cell biology with in planta transport assay using radioactive cesium, and heterologous system such as yeast, as well”.

These transporters are first step forward towards the basic understanding of potassium-independent cesium transport in plant and promise for future bioremediation. Based on their current finding and proposed model, it suggests that possibly more potassium-independent cesium transporters are yet to discover in plant. Abidur lab is working on finding other unknown cesium transporters. Deciphering the basic mechanism and finding more transporters in this regard will help to develop phytoremediation technique possible and translate this mechanism from model plant to crop plants, as these reported transporters are also conserved in crop plants and other species.

Featured image: Proposed model suggested by researchers, where ABCG33 and ABCG37 uptake cesium inside the plant cell in a potassium-independent manner © Abidur Rahman


Reference: Mohammad Arif Ashraf, Takashi Akihiro et al., “ATP Binding Cassette Proteins ABCG37 and ABCG33 function as potassium-independent cesium uptake carriers in Arabidopsis roots”, Molecular Plant, 2021. https://doi.org/10.1016/j.molp.2021.02.002


Provided by Iwate University, Japan

How Bacteria Hunt Bacteria? (Biology)

Predator-prey relationships between bacteria could provide ideas for new antibacterial strategies.

The research team led by Dr. Christine Kaimer from the Microbial Biology department at Ruhr-Universität Bochum (RUB) has taken a close look at predatory bacteria, which feed on other bacteria. Through microscopic examinations and protein analyses, they characterized the strategies used by the soil bacterium Myxococcus xanthus: It combines several mechanisms to kill structurally different prey bacteria, and also works in groups where necessary. These observations might be useful for the future development of new antibacterial strategies. The team reports in the journal Applied and Environmental Microbiology on 12 February 2021.

Bacterial groups in search of food

We commonly know predator-prey relationships from the animal kingdom, but they are also a survival strategy of certain bacteria: bacterial predators actively kill bacteria of other species in order to feed on them. The predatory species include many myxobacteria, which are widespread in the soil and display unique behavioural patterns: many cells assemble into large groups and go in search of food together or, in the event of nutrient limitation, build three-dimensional fruiting bodies. “The motility mechanisms of myxobacteria are very well investigated, but there are still many unanswered questions on the molecular processes of predation and their significance in complex bacteria communities,” says Christine Kaimer.

The Bochum-based biology team is investigating bacterial predation behaviour using the model of the soil bacterium Myxococcus xanthus, which is known to use a wide range of different microorganisms as prey. “We wondered, which mechanisms these predators use to kill structurally different prey bacteria,” explains Kaimer. “To address this, we carefully observed the predation behaviour of M. xanthus against different prey under the microscope and also compared the efficacy of the different protein fractions of the predator cells.”

Direct contact or contact in combination with proteins

The experiments have shown that several mechanisms are combined in different ways: the prey cells are initially killed by a predator cell in direct cell-cell contact. For gram-negative prey bacteria with a thin cell wall, this is sufficient to dissolve the cell and access the nutrients inside. To break down gram-positive prey bacteria with a thick cell wall, the predator needs additional proteins, which are realeased into the surrounding area. “The formation of larger predator groups seems to be particularly important for this,” explains Christine Kaimer.

These findings provide an important starting point to further reveal bacterial predation mechanisms. In the future, the researchers hope to gain insights into the dynamic interactions in bacterial communities and possibly obtain impulses for the development of new antibacterial strategies.Funding

The work was funded by a start-up grant from the Mercator Research Center Ruhr (MERCUR An-2016-0033) and the German Research Foundation (DFG research grant Ka 3361/3-1).

Featured image: This is what it looks like when a bacterium preys. © Biologie der Mikroorganismen


Reference: Kirstin Arend, Janka Schmidt, Tim Bentler, Carina Lüchtefeld, Daniel Eggerichs, Hannah Hexamer, Christine Kaimer: Myxococcus xanthus predation of gram-positive or gram-negative bacteria is mediated by different bacteriolytic mechanisms, in: Applied and Environmental Microbiology, 2021, DOI: 10.1128/AEM.02382-20


Provided by Ruhr Universität Bochum

HKU Planetary Scientists Discover Evidence For a Reduced Atmosphere on Ancient Mars (Planetary Science)

Both Earth and Mars currently have oxidising atmospheres, which is why iron-rich materials in daily life develop rust (a common name for iron oxide) during the oxidation reaction of iron and oxygen. The Earth has had an oxidising atmosphere for approximately two and a half billion years, but before that, the atmosphere of this planet was reducing – there was no rust. 

The transition from a reduced planet to an oxidised planet is referred to as the Great Oxidation Event or GOE. This transition was a central part of our planet’s evolution, and fundamentally linked to the evolution of life here – specifically to the prevalence of photosynthesis that produced oxygen. Planetary geologists at HKU have discovered that Mars underwent a great oxygenation event of its own – billions of years ago, the red planet was not so red.  

The discovery was published recently in Nature Astronomy in a paper led by research postgraduate student Jiacheng LIU and his advisor Associate Professor Dr Joe MICHALSKI, both affiliated with the Research Division for Earth and Planetary Science and Laboratory for Space Research. The researchers used infrared remote sensing and spectroscopy to measure the molecular vibration of the material on the Martian surface from orbit, in order to reveal the mineralogy and geochemistry of ancient rocks on Mars. Through detailed comparisons of infrared remote sensing data and data collected in the laboratory here on Earth, the team showed that ancient rocks on Mars exposed at the surface had been weathered under reducing conditions, indicating a reduced atmosphere did exist. 

Many people are aware that Mars is cold and dry now, but ~ 3.5 billion years ago, it was warmer and wetter. It was warm enough to allow the formation of river channels, lakes and minerals that formed by interaction with water. Scientists who have used mathematical models to constrain the conditions of an early Martian atmosphere, have concluded that greenhouse warming occurred, but they also concluded from their models that the greenhouse must have included reduced gases rather than carbon dioxide, implied that a reducing atmosphere might have existed. Yet until now, there has not been any evidence that the reduced atmosphere of early Mars actually occurred. This work indicates that it did exist.

A 3-dimensional view of weathered bedrock shows the exposure of Fe-rich red rocks beneath Fe-depleted blue-toned rocks in a crater wall. © University of Hong Kong

This project involved detailed infrared remote sensing of Mars, using infrared spectroscopy to map minerals in exposed, weathered rock units. The work was built on detailed analysis of weathered volcanic rocks in Hainan Island in southwestern China, where thick sequences of basalt, similar to volcanic rocks on Mars occur. Jiacheng Liu analysed the altered rocks systematically using infrared spectroscopy in the laboratory and produced a paper on that research published recently in Applied Clay Science

“Jiacheng has carried out a truly excellent PhD project, built on careful analysis in the laboratory and application of those laboratory results to remote sensing of Mars,” Dr Michalski commented, “Jiacheng has built on his detailed work on samples from Hainan Island to show that similar mineralogical trends occurred in rocks on Mars.”

Assistant Professor Dr Ryan MCKENZIE from Research Division for Earth and Planetary Science is also impressed by these findings. “This is a rather remarkable study with findings that will significantly impact how we understand the early evolution of terrestrial planets and their surface environments. The transition from a reducing to oxidising atmosphere on Earth ~2.5 billion years ago was only possible because the existence of life, as oxygen is a waste product of metabolic processes like photosynthesis. Without microbes producing oxygen, it would not accumulate in our atmosphere, and we could not be here. While there are certainly differences in the local conditions Mars and Earth have been subjected to during their evolutionary histories, my mind can’t help but start thinking about what Jiancheng’s results may mean for a potential early Martian biosphere,” Dr McKenzie remarked.

As China’s first mission to Mars Tianwen-1 is underway – has successfully arrived in Mars orbit on February 10 and set to land on Mars in May 2021, scientists are preparing for an exciting year of Mars exploration and discovery. This work demonstrates how spectroscopy and remote sensing lead to fundamental discoveries of significant importance for understanding Mars’ history. As we begin to understand the most ancient history of Mars, researchers are ready to directly search of any signatures that life might have once existed on ancient Mars, and HKU plans to be at the centre of this great scientific adventure. 

Featured image: The blue-toned rocks in the upper-left of the image are depleted in iron because it was removed during weathering on ancient Mars. This is geological evidence that iron was lost from the rocks in reduced conditions. © University of Hong Kong


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Provided by University of Hong Kong

Cloudy Eyes Caused By Protein Imbalance (Medicine)

Cataracts: new model explains origins of the eye condition

Cataracts are the most common eye ailment in humans. However, the exact processes leading to this condition are not fully understood. A team of researchers headed by the Technical University of Munich (TUM) has now discovered that the composition of the protein solution plays a decisive role. Their conclusions are contrary to prevailing opinion in the field.

The cells in the lens consist of a highly concentrated protein solution that is normally clear. “When the balance of the proteins in the lens is destroyed, they clump together and the lens becomes cloudy,” says Prof. Johannes Buchner of the Chair of Biotechnology at TUM. This results in the condition known as cataracts.

The clouding can have different causes. Because the proteins in the lens are formed in the embryo and are not replaced, damage can accumulate over the years, ultimately causing the lens to cloud over. That is why cataracts occur mainly in older people. But some individuals have a genetic predisposition to the eye condition, in which proteins in the lens mutate. In these cases, cataracts are present at birth or appear during childhood.

Unstable proteins eliminated immediately

The scientists studied strains of mice affected by hereditary cataracts. They worked with the research group surrounding Jochen Graw, an expert in eye lenses who until 2019 was a professor at the Institute of Development Genetics at Helmholtz Zentrum München.

Until now, the prevailing view said that only the defective proteins in the eye were reacting with one another and forming clumps. But Buchner’s team has now shown that, in the mice with “genetic cataracts”, this was not the case. “We discovered that the mutated, unstable proteins in the lens were not there,” says Buchner. “They are eliminated immediately.” Instead the ‘healthy’ proteins clump together. “Our model, based on these new insights, says that the balance between the various proteins, or their ratios to one another, is important. When one of these components is missing, the remaining ones interact and form clumps.” 

Important step for cataract treatment

Many studies have been carried out to understand the causes of cataracts. “But never before has there been such a comprehensive investigation of the lenses in mice, comparing wild populations and mutants,” says Buchner. The new insights are an important step in the search for new treatment methods for cataracts. The most common method is surgery, in which artificial lenses are implanted in the eye. 

“If you understand exactly what is happening, you can also think about ways that might use medication to disrupt the bad interactions,” says Buchner. “But we have a long way to go – and first we need to show that the proposed model also applies to the lens in the human eye.”

Featured image: In cataracts, the lens of the eye, which is actually clear, becomes cloudy.Image: Uli Benz / TUM


Publications:

Schmid, P.W.N., Lim, N.C.H., Peters, C. et al.:
Imbalances in the eye lens proteome are linked to cataract formation.
Nat Struct Mol Biol 28, 143–151 (2021). https://www.nature.com/articles/s41594-020-00543-9


Provided by TUM