Hexbyte Glen Cove Advanced imaging reveals new cellular and molecular details of coral-algae relationship

Hexbyte Glen Cove

A branching Acropora yongei coral. This 40x magnified image was captured using a handheld digital microscope. Credit: Scripps Institution of Oceanography at UC San Diego / Angus Thies.

Researchers at UC San Diego’s Scripps Institution of Oceanography have discovered a novel molecular process that corals use to control the subcellular environment of the algae that live inside them.

A specialized protein controls the fluctuating day-to-night transfer of nitrogen and carbon dioxide through the coral’s to the . The process is important because the coral and algae live in a mutually beneficial relationship called symbiosis. Although the team expected to find the protein, they could not have predicted the day-night changes in the intracellular areas they observed.

“We show that the interface between the animal hosts and the plants that live inside them is a dynamically controlled microenvironment,” said Angus Thies, a doctoral student who works in the laboratory of Scripps Oceanography marine physiologist Martin Tresguerres. Thies and his co-authors, who include scientists at the University of Manitoba in Canada, describe the first direct observations of the cellular interface between corals and their symbiotic algae in the March 11 issue of Science Advances. The study was supported by the National Science Foundation (NSF) through a grant to Tresguerres and a fellowship to Thies.

Until recently, the findings reported in Science Advances would have been nearly impossible to obtain. Tresguerres’s group already had invested years in pioneering how best to prepare corals for microscopy science. What clinched the achievement, though, was the team’s acquisition of an apparatus known as a laser confocal super-resolution system that was funded by the Arthur M. and Kate E. Tode Research Endowment in Marine Biological Sciences at UC San Diego.

This system permitted the team to image the coral membrane that surrounds the algae at a resolution more than double that of the lab’s previous microscope. The new system can isolate features only 120 nanometers apart. A , by comparison, is 90,000 nanometers thick.

“Decades of studies show that corals seem to regulate how much nitrogen they give to their algae,” Tresguerres said. But if the algae receive too much nitrogen, they may grow and multiply too quickly, disrupting the symbiosis.

“Just like humans, coral health and disease can be tracked to the cellular level. When things go right on the cellular level, the coral thrives. And when things go wrong, it usually leads to malfunction or disease, potentially including ‘bleaching.’ What we call the symbiosis interface might be the most important interface, the most important membrane, on the entire reef,” Tresguerres said.

Symbioses form important biological interactions in many living systems. For example, humans have a symbiotic relationship with the bacteria that fill our digestive tract. But there’s a difference.

“In humans, bacteria live outside our cells; for example, in the inside of our intestines and on our skin. But in corals, these algae live inside cells of the host animal itself,” Thies said. “It’s a very tight space. It’s like having a roommate forever and you hope it’s a really good roommate. You want to keep everyone as happy as possible.”

Left: Super-resolution confocal image of a coral host cell and its intracellular symbiotic alga. Right: 3D rendering using Imaris software which allows better visualization of the cellular patterns. Credit: Scripps Institution of Oceanography at UC San Diego

At first glance, corals might look like colorful rocks that sprout pretty little polyps. “They are, in fact, among the most important animals on Earth,” Thies said. Approximately one billion people rely on coral reef ecosystems either directly or indirectly for their food and yet scientists know very little about how corals function at the cellular level.

The Science Advances study identified a cellular mechanism that mediates nitrogen delivery to the symbiotic algae during normal conditions. This is a significant finding because, to understand what happens when a process goes wrong, scientists first need to establish how it works in healthy corals. But how is this process altered by climate change or pollution?

“Perhaps, under certain conditions of climate change, this mechanism is disrupted and can lead to bleaching because the algae do not have enough or they have too much nitrogen,” Tresguerres said. “That opens the door for a lot of research, both by us and also other labs.”

Thies, who received his undergraduate degree in marine biology at UC San Diego in 2017, began working on this project as an undergraduate student in Tresguerres’s laboratory. He has continued the project as an NSF Graduate Fellow and a Scripps Oceanography Doctoral Scholar Fellow.

“Corals are not easy organisms to work with,” Thies said. “Corals require a lot of aquarium care because they’re complicated symbiotic animals. Sometimes, they’re hard to keep happy.” But a team of six UC San Diego undergraduate and graduate students did exactly that, earning an acknowledgment in the Science Advances paper for their efforts.

Although the Tresguerres lab studies many different organisms, what they find in one organism often appears in another one no matter how distantly related. Even though corals, sharks, and algae may share some of the same enzymes—highly specialized proteins—, each organism puts them to different uses. Even two separate coral species that dwell at the same depth might employ quite different adaptations.

Proteins and enzymes serve as cellular building blocks that Tresguerres compared to LEGO bricks. In a , many enzymes support symbiosis. Similar enzymes in an Osedax worm, which feeds on whale carcasses, help the worm eat through bone. And in shark and stingray gills, similar enzymes are involved in maintaining blood acidity within healthy levels.

“I find Evolution fascinating, especially at the cellular level,” Tresguerres said. “The proteins are the same, but then they partner with other proteins or they’re in different cellular compartments and put in a wildly different function.”

Besides Thies and Tresguerres, the research team included Alex R. Quijada-Rodriguez, Haonan Zhouyao, and Prof. Dirk Weihrauch of the University of Manitoba, Canada.



More information:
Angus Thies et al, A Rhesus channel in the coral symbiosome membrane suggests a novel mechanism to regulate NH3 and CO2 delivery to algal symbionts, Science Advances (2022). DOI: 10.1126/sciadv.abm0303. www.science.org/doi/10.1126/sciadv.abm0303

Citation:
Advanced imaging reveals new cellular and molecular details of coral-algae relationship (2022, March 11)
retrieved 13 March 2022
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Hexbyte Glen Cove Realtime imaging of female gamete formation in plants thumbnail

Hexbyte Glen Cove Realtime imaging of female gamete formation in plants

Hexbyte Glen Cove

Development of the female gamete was observed over 20 hours, clearly showing the division of the nuclei and formation of the egg, central and synergid cells. Credit: Issey Takahashi

Scientists from Nagoya University, Yokohama City University and Chubu University have developed a system which enables the live imaging of the formation of the female gamete in plants.

In flowering plants, the sperm cell and egg cell meet and fertilization takes place in the flower. While are made in the pollen, are made in the ovule, the structure that becomes the seed. However, as the ovule is buried deep within the pistil, it has thus far been impossible to observe the formation of the egg cell in living plants.

The team, led by Dr. Daisuke Kurihara and Dr. Tetsuya Higashiyama of Nagoya University Institute of Transformative Bio-Molecules (WPI-ITbM), Dr. Daichi Susaki of Yokohama City University Kihara Institute for Biological Research and Dr. Takamasa Suzuki of Chubu University College of Bioscience and Biotechnology, using the ovule culturing technology that they had developed previously, succeeded in capturing images of the egg cell being formed inside the ovule. On top of that, they were able to isolate the egg cell and its neighboring , and by analyzing the genes expressed in these few cells, identify how the cells adjoining the egg cell determine its fate.

Living things which carry out sexual reproduction produce offspring via a fertilization process involving male and female gametes. In animals, the female gamete (the egg) is produced by meiosis, a type of cell division that halves the number of chromosomes present in the cell. However, the process in flowering plants is rather more lengthy. Following meiosis, karyomitosis (nuclear division) takes place three times within the cell, resulting in the production of a single cell with eight . This cell then divides, producing cells with a variety of different roles including two gametes, the egg cell and central cell, and the synergid cells. However, it was not yet understood precisely how the two female gametes were produced among the seven new cells that result from this process of division.

Using an ovule culturing method that they had developed previously, the research team attempted the observation in real time of the formation of the female gamete in Arabidopsis thaliana. They saw that when the first nuclear division takes place, the resulting two nuclei go to the opposite ends of the cell. Dividing again into four, the nuclei then line up along the edge of the cell. Finally, dividing again into eight, the plasma membranes are constructed around the nuclei, forming the cells which are attached to the two gametes (the egg cell and central cell). Having observed 157 cases of this division, they found that the nuclei close to where the pollen tube penetrates would become the nuclei of the synergid, egg and central cells, demonstrating that the position of the nuclei within the cell has a strong correlation with cell fate.

Continuing, in order to find out when the various cells’ fates are determined, they analyzed the time at which expression of the specific transcription factor myb98, important for the differentiation and function of the synergid cells, commenced. They found that myb98 begins to be expressed very shortly after the nuclei divide into 8 and are enclosed by the plasma membranes. Given that the specific transcription factor for the egg cell can also be found in the egg cell at the same early stage, it can be considered that cell fate is determined immediately after the formation of the plasma membranes, or possibly even earlier.

The time at which cell fate is determined is significant because it gives us an insight into how plants remain adaptable to environmental conditions by flexibly changing cell fate and thus ensuring the survival of crucial cells such as gametes.

Looking to the future, the research team’s focus will be on discovering how the cell fate change is accomplished, and explaining its . Once the molecular mechanism has been analyzed, it is expected that this field of research will contribute to the development of methods to increase plant fertilization rates and environmental resistance, offering the prospect of solving key issues in food supply that affect millions of people around the world.



More information:
Daichi Susaki et al, Dynamics of the cell fate specifications during female gametophyte development in Arabidopsis, PLOS Biology (2021). DOI: 10.1371/journal.pbio.3001123

Citation:
Realtime imaging of female gamete formation in plants (2021, April 2)
retrieved 5 April 2021
from https://phys.org/news/2021-04-

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Hexbyte Glen Cove New imaging method views soil carbon at near-atomic scales thumbnail

Hexbyte Glen Cove New imaging method views soil carbon at near-atomic scales

Hexbyte Glen Cove

Credit: CC0 Public Domain

The Earth’s soils contain more than three times the amount of carbon than is found in the atmosphere, but the processes that bind carbon in the soil are still not well understood.

Improving such understanding may help researchers develop strategies for sequestering more carbon in soil, thereby keeping it out of the atmosphere where it combines with oxygen and acts as a greenhouse gas.

A new study describes a breakthrough method for imaging the physical and chemical interactions that sequester carbon in soil at near atomic scales, with some surprising results.

The study, “Organo-organic and Organo-mineral Interfaces in Soil at the Nanometer Scale,” was published Nov. 30 in Nature Communications.

At that resolution, the researchers showed—for the first time—that soil carbon interacts with both minerals and other forms of carbon from organic materials, such as bacterial cell walls and microbial byproducts. Previous imaging research had only pointed to layered interactions between carbon and minerals in soils.

“If there is an overlooked mechanism that can help us retain more carbon in soils, then that will help our climate,” said senior author Johannes Lehmann, the Liberty Hyde Bailey Professor in the School of Integrative Plant Science, Soil and Crop Sciences Section, in the College of Agriculture and Life Sciences. Angela Possinger Ph.D. ’19, who was a graduate student in Lehmann’s lab and is currently a postdoctoral researcher at Virginia Tech University, is the paper’s first author.

Since the resolution of the new technique is near atomic scale, the researchers are not certain what compounds they are looking at, but they suspect the carbon found in soils is likely from metabolites produced by soil microbes and from microbial cell walls. “In all likelihood, this is a microbial graveyard,” Lehmann said.

“We had an unexpected finding where we could see interfaces between different forms of carbon and not just between carbon and minerals,” Possinger said. “We could start to look at those interfaces and try to understand something about those interactions.”

The technique revealed layers of carbon around those organic interfaces. It also showed that nitrogen was an important player for facilitating the chemical interactions between both organic and mineral interfaces, Possinger said.

As a result, farmers may improve soil health and mitigate climate change through sequestration by considering the form of nitrogen in soil amendments, she said.

While pursuing her doctorate, Possinger worked for years with Cornell physicists—including co-authors Lena Kourkoutis, associate professor of applied and , and David Muller, the Samuel B. Eckert Professor of Engineering in Applied and Engineering Physics, and the co-director of the Kavli Institute at Cornell for Nanoscale Science—to help develop the multi-step method.

The researchers planned to use powerful electron microscopes to focus electron beams down to sub-atomic scales, but they found the electrons modify and damage loose and complex soil samples. As a result, they had to freeze the samples to around minus 180 degrees Celsius, which reduced the harmful effects from the beams.

“We had to develop a technique that essentially keeps the soil particles frozen throughout the process of making very thin slices to look at these tiny interfaces,” Possinger said.

The beams could then be scanned across the sample to produce images of the structure and chemistry of a sample and its complex interfaces, Kourkoutis said.

“Our physics colleagues are leading the way globally to improve our ability to look very closely into material properties,” Lehmann said. “Without such interdisciplinary collaboration, these breakthroughs are not possible.”.

The new cryogenic electron microscopy and spectroscopy technique will allow researchers to probe a whole range of interfaces between soft and hard materials, including those that play roles in the function of batteries, fuel cells and electrolyzers, Kourkoutis said.



More information:
Angela R. Possinger et al. Organo–organic and organo–mineral interfaces in soil at the nanometer scale, Nature Communications (2020). DOI: 10.1038/s41467-020-19792-9

Citation:
New imaging method views soil carbon at near-at