“The results are highly relevant for combating fungal infections in clinical practice, veterinary medicine and agriculture,” says Professor Ulrich Kück, Senior Professor in General and Molecular Botany at RUB. He cooperated for the project with the Bochum researcher Dr. Tim Dahlmann and the team headed by Professor Dr. Joe Heitman, who is currently based at Duke University in North Carolina and has been a visiting professor at RUB on several occasions.

Number of fungal infections on the rise

“In the western hemisphere, the number of people with a lowered immune defence is increasing, because life expectancies are rising rapidly and treatment with immunosuppressants after organ transplants is becoming more common,” explains Ulrich Kück. “This is associated with an increase in fungal infections.” Cryptococcus neoformans is one of the most significant human pathogenic fungi responsible for so-called cryptococcosis. It triggers acute infections in immunocompromised patients; and the mortality rate may be as high as 70 per cent. This is because fungal strains that are resistant to the drugs often evolve in hospitals, which makes treatment more difficult. So far, it was unclear which cellular and genetic mechanisms lead to this resistance.

So-called transposons, however, were known to play a role in the resistances. Transposons are jumping genes, i.e. DNA segments that can change their position in the genome and thus affect the function of genes. If a transposon jumps into a gene that’s critical for susceptibility to a drug, it’s possible for resistance to emerge. The mobility of the transposons is controlled by regulatory RNAs, so-called small interfering RNA, or siRNA for short.

RNA mechanism causes resistance

In their current study, the researchers discovered gene mutations in resistant isolates that led to siRNA control being switched off. By introducing an intact copy of the gene, it was possible to restore siRNA control; as a result, the researchers were able to prevent the transposons from jumping and shed light on the cause of resistance. Due to their small size, the gene segments that code for siRNAs are not easy to find in the genome. Tim Dahlmann managed to locate them with special bioinformatic analyses. By identifying the resistance mechanisms, it will be possible to use them for the treatment of mycoses in humans in the future.

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Materials provided by Ruhr-University Bochum. Original written by Julia Weiler. Note: Content may be edited for style and length.

A bacterial syringe delivers a deadly enzyme

The mechanism of action of Tc toxins has only recently been uncovered to a greater extent by the work of Stefan Raunser’s team in structural biology at the MPI Dortmund. “Unraveling the structure of the Tc toxin subunits and their assembly by cryo electron microscopy (cryo-EM) enabled us to understand the key steps of toxin activation and membrane penetration,” says Raunser. The scientists showed that the subunits of the Tc toxin complex work together like a syringe: once the subunits are assembled, structural changes in the complex trigger the opening of a cocoon which contains a toxic enzyme, which is then secreted in a unique injection mechanism via a channel into the host cell. There, it unfolds its deadly effect by disturbing the regulation of the cell’s cytoskeleton, which consists of a network of polymerized actin (F-actin) filaments involved in many essential cellular processes.

Setting up the opponent by reducing the striking distance

“For a long time, we struggled with obtaining a complete picture of the intoxication process, since we lacked the structural data of the secreted enzymes, one of which is TccC3,” reflects Raunser. Until recently, it was only known that TccC3 transfers an ADP-ribose group to actin promoting its aberrant polymerization, which leads to actin filament clumping. “TccC3 is what we call a “difficult” system for structural investigations due to its size and high flexibility,” says Hartmut Oschkinat. “Only by applying solution NMR, could we overcome this challenge and visualize the protein’s 3D structure for the first time.” By fusing two further cryo-EM snapshots of TccC3 bound to F-actin and of the modified F-actin alone, the scientists have uncovered the enzyme’s unique mechanism of action. “TccC3 acts like a boxer who sets up his opponent to make him vulnerable to the attack” says Stefan Raunser. In the first step, the enzyme binds to a region between two consecutive actin subunits of F-actin. TccC3 then opens a gate, which brings the molecule NAD+ that contains the ADP-ribose group within striking distance to a reactive site on actin. Once the bulky ADP-ribose group is transferred to F-actin, it is no longer accessible for its depolymerizing factors, whereby F-actin can no longer be broken down and thus clumps.

In addition to this discovery, the scientists’ findings have helped formulate an explanation for the strikingly high efficiency of the enzyme. When the enzyme detaches from F-actin, its gate mechanism prevents a futile rebinding to the already modified actin as preparation for the next attack. “It is amazing how all these mechanisms evolved to increase the toxins potency to the max. And nature did quite a good job since botulinum toxins, ricin and other biotoxins are still considered the most toxic substances known,” Raunser concludes.

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Materials provided by Max Planck Institute of Molecular Physiology. Note: Content may be edited for style and length.

Cured and processed meats, such as salami and bacon, are often treated with nitrite or nitrate salts to keep them looking and tasting fresh. Though nitrate is relatively stable, it can be converted to the more reactive nitrite ion in the body. When in the acidic environment of the stomach or under the high heat of a frying pan, nitrite can undergo a reaction to form nitrosamines, which have been linked to the development of various cancers. Some methods to determine nitrite levels in foods already exist, but they are not very consumer-friendly and often require expensive and laborious techniques and instruments. To help consumers make more informed decisions, Saúl Vallejos, José M. García and colleagues wanted to develop an easy-to-use nitrite quantification system.

To accomplish this, the researchers developed a film they called “POLYSEN,” which stands for “polymeric sensor,” made of four monomers and hydrochloric acid. Disks punched from the material were placed on meat samples for 15 minutes, allowing the monomer units and acid in the film to react with nitrite in a four-step azo coupling reaction. The disks were then removed and dipped in a sodium hydroxide solution for one minute to develop the color. When nitrite was present, the film’s yellowish hue deepened with higher nitrite levels in the food. To quantitate the color change, the researchers created a smartphone app that self-calibrates when a chart of reference disks is photographed in the same image as the sample disks.

The team tested the film on meats they prepared and treated with nitrite, in addition to store-bought meats, and found that the POLYSEN-based method produced results similar to those obtained with a traditional and more complex nitrite detection method. In addition, POLYSEN complied with a European regulation for migration of substances from the film to the food. The researchers say the new approach could be a user-friendly and inexpensive way for consumers to determine nitrite levels in foods.

The authors acknowledge funding from La Caixa Foundation and the Spanish Agencia Estatal de Investigación. They also acknowledge the support and collaboration of the company Inforapps.

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Materials provided by American Chemical Society. Note: Content may be edited for style and length.

Rice researchers set up aMicrosoft HoloLens as a mixed-reality sensor to feed VegSense, their application to measure understory vegetation, plant life that grows between the forest canopy and floor.

A proof-of-concept study by graduate student Daniel Gorczynski and bioscientistLydia Beaudrot shows VegSense could be a suitable alternative to traditional classical field measurements at a low cost.

Their study in Methods in Ecology and Evolution shows the hardware-software combination excels at quantifying relatively mature trees in the wild, which is one measure of a forest’s overall health.

Gorczynski came up with the idea to try HoloLens, commonly marketed as a productivity tool for manufacturing, health care and education. He developed the open-source software for the device and noted that while the combination is less effective at picking up saplings and small branches, there’s ample room for improvement.

Gorczynski said he was introduced to mixed-reality sensing while an undergraduate at Vanderbilt University and recognized its potential for biological studies. “It seemed sort of like a natural fit,” he said. Gorczynski brought the idea to Beaudrot in 2019 shortly after his arrival at Rice.

The combination of stock hardware and custom software cost far less than systems based onlidar (for “light detection and ranging”) most often used in three-dimensional field studies, said Gorczynski, who developed VegSense on a platform geared more toward 3D games and interactive experiences than hard science.

Field tests at Houston’s Memorial Park showed that at least for mature trees, the smaller solution is just as good. In their case study, VegSense easily detected 48 of 50 such trees in the target area, a circle about 30 feet in diameter that Gorczynski walked, looking up, down and around to build the 3D database. (“Imagine an asterisk with a circle around it,” he said, describing the data-capture pattern.)

“For this study, we wanted to be really deliberate in trying to replicate more traditional understory vegetation structure measurements,” Gorczynski said. “We tried to get that level of detail.”

What he sees as he scans the environment is a holograph-like grid pattern that tracks the surfaces of vegetation. “What’s really cool about that is you can see what the scanner is picking up, but also the spots you missed,” Gorczynski said. “The idea is to get the mesh to cover as much of the vegetation as possible because that’s what gets you the best scan.”

“The results were so nice that Dan quickly wrote it up for publication,” Beaudrot said, noting that Gorczynski expanded his validation of the gear during a subsequent field trip to Tanzania, the focus of one of 15 tropical forests in a recent rainforest study by the Rice group.

“This device can facilitate a lot of great ecological research, particularly because it’s so cost-effective,” she said. “Collecting vegetation information on the forest floor right now is really hard to do without a lot of manual labor, or a really expensive lidar system.”

“So this is a groundbreaking, cost-effective device,” Beaudrot said. “It’s not going to give you the same resolution data that lidar will, but this is just the first application. We hope making VegSense open-source to the ecological research community will spur all the potential ways it can be developed.”

Northrop Grumman, Conservation International and Rice supported the research.

Video: https://youtu.be/dBHfxvhMChU

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Materials provided by Rice University. Original written by Mike Williams. Note: Content may be edited for style and length.

The discovery involves a once maligned collection of molecules called reactive oxygen species (ROS), which are produced by anything that uses oxygen, like animals, people and plants. But Ron Mittler at MU has uncovered a redeeming quality of ROS — their role as a communication signal that can indicate whether plants are stressed out.

“When stressors from heat and drought are added together, plants don’t have ground water to draw from, so they close the stomata [leaf pores], and this makes the leaves become really hot,” said Mittler, whose appointment is in the College of Agriculture, Food and Natural Resources. “This is why the combination of drought and heat is really dangerous, because the leaf temperature is much higher than with a plant subjected to just heat. The change can be anywhere between two and four degrees, and that can make the difference between life and death.”

Plant stress is also tied to crop loss, but existing analytical research on the subject has typically focused on how crops react to just one stressor. However, Mittler said a plant’s survival rate will dramatically decrease as the number of stressors continues to increase to three to six different stressors. The key, he said, is to keep ROS levels in check. Either too much or too little can be damaging, but an optimum level of ROS can be considered safe for life.

Hooked on science

Born and raised in Israel, Mittler wanted to be a veterinarian while growing up. But, after enrolling at the Hebrew University of Jerusalem, he recalls spending a summer in the late 1980s as an undergraduate student working in an agriculture lab, where he got “hooked” on science — particularly the role of ROS in plants. Mittler has been studying ROS ever since.

“At the time, we were trying to identify why certain cell lines were more resistant to salinity than others,” he said. “That was my first-ever scientific research problem. But then I started to work on desert plants, and from there on reactive oxygen species and blue green algae.”

“Reactive oxygen species signaling in plant stress responses,” was published in Nature Reviews Molecular Cell Biology, a journal of Nature. Other authors include Sara Zandalinas and Yosef Fichman at MU; and Frank Van Breusegem at Ghent University in Belgium.

This study was supported by funding from the National Science Foundation (IOS-2110017, IOS-1353886, MCB-1936590 and IOS-1932639), the National Institutes of Health, the University of Missouri Interdisciplinary Plant Group, University of Missouri, Research Foundation — Founders (project G0D7914N) and the Excellence of Science Research (project 30829584). The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding agencies.

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Materials provided by University of Missouri-Columbia. Note: Content may be edited for style and length.