Tag Archives: #photosynthesis

New Study Sheds Light on Evolution of Photosynthesis (Botany)

A Rutgers-led study sheds new light on the evolution of photosynthesis in plants and algae, which could help to improve crop production.

The paper appears in the journal New Phytologist.

The scientists reviewed research on the photosynthetic amoeba Paulinella, which is a model to explore a fundamental question about eukaryote evolution: why was there a single origin of algae and plants? That is, why did photosynthesis by primary plastid endosymbiosis not originate multiple times in the tree of life?

Photosynthesis is the process by which plants and other organisms use sunlight to synthesize foods from carbon dioxide and water, which generates oxygen as a byproduct.

Endosymbiosis is a relationship between two organisms wherein one cell resides inside the other. This interaction, when stable and beneficial for the “host” cell, can result in massive genetic innovation. Despite its critical evolutionary role, there is limited knowledge about how endosymbiosis is initially established.

Primary plastid endosymbiosis, which evolved about 1.5 billion years ago, is the process in which a eukaryote — which are organisms such as plants and algae whose cells have a membrane-bound nucleus and tiny organs called organelles — engulfs a prokaryote, which are organisms such as bacteria that lack a membrane-enclosed nucleus. The plastid is a membrane-bound organelle within the cells of plants and algae.

“It turns out that photosynthesis results in enormous risks because it produces harmful chemicals and heat as byproducts that can damage the host cell,” said senior author Debashish Bhattacharya, a Distinguished Professor in the Department of Biochemistry and Microbiology at Rutgers University-New Brunswick. “Therefore, creating a novel organelle is a highly complex process that makes it fleetingly rare in evolution. Paulinella, which is the only known case of an independent plastid primary endosymbiosis other than in algae and plants, offers many clues to this process that helps explain why it is so rare.”

The origin of photosynthesis in algae and plants changed our planet by providing a major source of oxygen and supporting many ecosystems, due to their primary production, of fixed carbon (sugars and lipids). Understanding how this critical process happened will help us potentially engineer it in synthetic systems as well as to improve crop production.

“Because Paulinella is an independent origin of photosynthesis, it provides key clues to how this process occurs and what costs it imposes on the host cell,” said lead author Timothy G. Stephens, a postdoctoral researcher at Rutgers. “The genome of Paulinella contains many independently evolved genes involved in photosynthesis and dealing with the associated stresses that can potentially be engineered in algae and plants could help to improve their ability to withstand stresses such as high light levels or salt stress.”

The findings are explained in two videos:

The study included researchers from the Carnegie Institution.

Featured image: The photosynthetic amoeba Paulinella. © Florian Raunecker


Reference: Stephens, T.G., Gabr, A., Calatrava, V., Grossman, A.R. and Bhattacharya, D. (2021), Why is primary endosymbiosis so rare?. New Phytol. https://doi.org/10.1111/nph.17478


Provided by Rutgers University

Researchers Propose Novel Approach to Enhance Heterogeneous Photosynthesis of Azo- compounds (Chemistry)

Photocatalytic reactions, which allow unlocking some chemical transformations under mild conditions that are unavailable to conventional ground-state pathways, can save energy consumption and improve intrinsic safety of the processes. As a sustainable and low-carbon technology, it has high potential in the commitment to carbon peak and carbon neutrality.

Continuous flow chemistry can, to a large extent, migrate the “light limitation” problem in traditional batch protocols, and the use of heterogeneous photocatalysis can overcome the disadvantages of difficult catalyst recovery in homogeneous systems. However, effective handling of the solid photocatalysis in continuous flow still remains a challenge.

In a study published in Chemical Engineering Journal, a team led by Prof. TANG Zhiyong and Assoc. Prof. ZHANG Jie at Shanghai Advanced Research Institute of the Chinese Academy of Sciences reported a novel approach to utilize the solid photocatalysis in continuous flow without clogging with the employment of gas–liquid-solid segmented flow. This approach, owning to the inner recirculation in liquid segments and the formed thin film, ensures the effective suspension of solid catalysts in flow, resulting in enhanced mass transfer and irradiation.

Azobenzene and azoxybenzene are important precursors in pigment industry, electronic industry and pharmaceutical industry. In this study, the selective synthesis of azo- compounds from nitrobenzene by graphitic carbon nitride (g-C3N4) photocatalysis was selected as model photocatalytic reaction. Through visual flow experiments, the model reaction under gas-liquid-solid segmented flow was investigated thoroughly. Meanwhile, the effects of flow behavior on the photoreaction performance were quantified.

Besides, the researchers found that the continuous flow could greatly shorten the reaction time. The photocatalytic reaction performance was very sensitive to the gas-liquid-solid segmented flow conditions, which needs to be carefully tuned.

Increasing inert gas fraction resulted in more stable segmented flow with shorter liquid segments and thinker liquid film. The maximum productivity per volume of the continuous photo-microreactor reached 26.1 mmol/h*L. Benefiting from the advantage of “numbering-up”, this value was more than 500 times that of the batch reactor (80 L) reported in the open literature.

These results demonstrated great potential of gas-liquid-solid segmented flow in the field of heterogeneous photocatalysis. This study provides a new route to utilize the heterogenous catalysis in continuous flow, which can be applied to intensify the synthesis of functional materials, fine chemicals and active pharmaceutical ingredients.


Reference: Yuhang Chen, Yaheng Zhang, Hongwei Zou, Minglei Li, Gang Wang, Min Peng, Jie Zhang, Zhiyong Tang, Tuning the gas-liquid-solid segmented flow for enhanced heterogeneous photosynthesis of Azo- compounds, Chemical Engineering Journal, Volume 423, 2021, 130226, ISSN 1385-8947, https://doi.org/10.1016/j.cej.2021.130226. (https://www.sciencedirect.com/science/article/pii/S1385894721018143)


Provided by Chinese Academy of Sciences

An Illuminating Possibility For Stroke Treatment: Nano-photosynthesis (Neuroscience)

Blocked blood vessels in the brains of stroke patients prevent oxygen-rich blood from getting to cells, causing severe damage. Plants and some microbes produce oxygen through photosynthesis. What if there was a way to make photosynthesis happen in the brains of patients? Now, researchers reporting in ACS’ Nano Letters have done just that in cells and in mice, using blue-green algae and special nanoparticles, in a proof-of-concept demonstration.

Strokes result in the deaths of 5 million people worldwide every year, according to the World Health Organization. Millions more survive, but they often experience disabilities, such as difficulties with speech, swallowing or memory. The most common cause is a blood vessel blockage in the brain, and the best way to prevent permanent brain damage from this type of stroke is to dissolve or surgically remove the blockage as soon as possible. However, those options only work within a narrow time window after the stroke happens and can be risky. Blue-green algae, such as Synechococcus elongatus, have been studied previously to treat the lack of oxygen in heart tissue and tumors using photosynthesis. But the visible light needed to trigger the microbes can’t penetrate the skull, and although near-infrared light can pass through, it is insufficient to directly power photosynthesis. “Up-conversion” nanoparticles, often used for imaging, can absorb near-infrared photons and emit visible light. So, Lin Wang, Zheng Wang, Guobin Wang and colleagues at Huazhong University of Science and Technology wanted to see if they could develop a new approach that could someday be used for stroke patients by combining these parts — S. elongatus, nanoparticles and near-infrared light — in a new “nano-photosynthetic” system.

The researchers paired S. elongatus with neodymium up-conversion nanoparticles that transform tissue-penetrating near-infrared light to a visible wavelength that the microbes can use to photosynthesize. In a cell study, they found that the nano-photosynthesis approach reduced the number of neurons that died after oxygen and glucose deprivation. They then injected the microbes and nanoparticles into mice with blocked cerebral arteries and exposed the mice to near-infrared light. The therapy reduced the number of dying neurons, improved the animals’ motor function and even helped new blood vessels to start growing. Although this treatment is still in the animal testing stage, it has promise to advance someday toward human clinical trials, the researchers say.

The authors acknowledge funding from the National Key Basic Research Program of China, the National Natural Science Foundation of China, the Chinese Ministry of Education’s Science and Technology Program, the Major Scientific and Technological Innovation Projects in Hubei Province, and the Joint Fund of Ministry of Education for Equipment Pre-research.

The paper’s abstract will be available on May 19 at 8 a.m. Eastern time here: http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.1c00719.

Featured image: Brain slices of mice that received nano-photosynthetic therapy (right) have fewer damaged neurons, shown in green, than control mice (left). © Adapted from Nano Letters 2021, DOI: 10.10.21/acs.nanolett.1c00719


Reference: Jian Wang, Qiangfei Su, Qiying Lv, Bo Cai, Xiakeerzhati Xiaohalati, Guobin Wang, Zheng Wang, and Lin Wang, “Oxygen-Generating Cyanobacteria Powered by Upconversion-Nanoparticles-Converted Near-Infrared Light for Ischemic Stroke Treatment”, Nano Lett. 2021.
https://doi.org/10.1021/acs.nanolett.1c00719


Provided by American Chemical Society

U-M Researchers Trace Path Of Light in Photosynthesis (Botany)

Three billion years ago, light first zipped through chlorophyll within tiny reaction centers, the first step plants and photosynthetic bacteria take to convert light into food.

Heliobacteria, a type of bacteria that uses photosynthesis to generate energy, has reaction centers thought to be similar to those of the common ancestors for all photosynthetic organisms. Now, a University of Michigan team has determined the first steps in converting light into energy for this bacterium.

“Our study highlights the different ways in which nature has made use of the basic reaction center architecture that emerged over 3 billion years ago,” said lead author and U-M physicist Jennifer Ogilvie. “We want to ultimately understand how energy moves through the system and ends up creating what we call the ‘charge-separated state.’ This state is the battery that drives the engine of photosynthesis.”

Photosynthetic organisms contain “antenna” proteins that are packed with pigment molecules to harvest photons. The collected energy is then directed to “reaction centers” that power the initial steps that convert light energy into food for the organism. These initial steps happen on incredibly fast timescales—femtoseconds, or one millionth of one billionth of a second. During the blink of an eye, this conversion happens many quadrillions of times.

Pictured is a schematic of the charge separation in the heliobacterial reaction center. Image credit: Hoang Nguyen
Pictured is a schematic of the charge separation in the heliobacterial reaction center. Image credit: Hoang Nguyen

Researchers are interested in understanding how this transformation takes place. It gives us a better understanding of how plants and photosynthetic organisms convert light into nourishing energy. It also gives researchers a better understanding of how photovoltaics work—and the basis for understanding how to build them better.

When light hits a photosynthetic organism, pigments within the antenna gather photons and direct the energy toward the reaction center. In the reaction center, the energy bumps an electron to a higher energy level, from which it moves to a new location, leaving behind a positive charge. This is called a charge separation. This process happens differently based on the structure of the reaction center in which it occurs.

In the reaction centers of plants and most photosynthetic organisms, the pigments that orchestrate charge separation absorb similar colors of light, making it difficult to visualize charge separation. Using the heliobacteria, the researchers identified which pigments initially donate the electron after they’re excited by a photon, and which pigments accept the electron.

Heliobacteria is a good model to examine, Ogilvie said, because their reaction centers have a mixture of chlorophyll and bacteriochlorophyll, which means that these different pigments absorb different colors of lights. For example, she said, imagine trying to follow a person in a crowd—but everyone is wearing blue jackets, you’re watching from a distance and you can only take snapshots of the person moving through the crowd.

“But if the person you were watching was wearing a red jacket, you could follow them much more easily. This system is kind of like that: It has distinct markers,” said Ogilvie, professor of physics, biophysics, and macromolecular science and engineering

Pictured is the ultrafast optical setup in the Laboratory for Ultrafast Multidimensional Optical Spectroscopy at the University of Michigan. Image credit: Yin Song and Rong Duan
Pictured is the ultrafast optical setup in the Laboratory for Ultrafast Multidimensional Optical Spectroscopy at the University of Michigan. Image credit: Yin Song and Rong Duan

Previously, heliobacteria were difficult to understand because its reaction center structure was unknown. The structure of membrane proteins like reaction centers are notoriously difficult to determine, but Ogilvie’s co-author, Arizona State University biochemist Kevin Redding, developed a way to resolve the crystal structure of these reaction centers.

To probe reaction centers in heliobacteria, Ogilvie’s team uses a type of ultrafast spectroscopy called multidimensional electronic spectroscopy, implemented in Ogilvie’s lab by lead author and postdoctoral fellow Yin Song. The team aims a sequence of carefully timed, very short laser pulses at a sample of bacteria. The shorter the laser pulse, the broader light spectrum it can excite.

Each time the laser pulse hits the sample, the light excites the reaction centers within. The researchers vary the time delay between the pulses, and then record how each of those pulses interacts with the sample. When pulses hit the sample, its electrons are excited to a higher energy level. The pigments in the sample absorb specific wavelengths of light from the laser—specific colors—and the colors that are absorbed give the researchers information about the energy level structure of the system and how energy flows through it.

“That’s an important role of spectroscopy: When we just look at the structure of something, it’s not always obvious how it works. Spectroscopy allows us to follow a structure as it’s functioning, as the energy is being absorbed and making its way through those first energy conversion steps,” Ogilvie said. “Because the energies are quite distinct in this type of reaction center, we can really get an unambiguous look at where the energy is going.”

Getting a clearer picture of this energy transport and charge separation allows the researchers to develop more accurate theories about how the process works in other reaction centers.

“In plants and bacteria, it’s thought that the charge separation mechanism is different,” Ogilvie said. “The dream is to be able to take a structure and, if our theories are good enough, we should be able to predict how it works and what will happen in other structures—and rule out mechanisms that are incorrect.”

Featured image: Pictured is the ultrafast optical setup in the Laboratory for Ultrafast Multidimensional Optical Spectroscopy at the University of Michigan. Image credit: Yin Song and Rong Duan


More information:


Provided by University of Michigan

The Ion Balance Influences The Efficiency Of Photosynthesis (Botany)

New role for ion transport proteins: As LMU biologist Hans-Henning Kunz shows, they are involved in gene regulation in chloroplasts.

Chloroplasts are the plants’ photosynthesis factories. They originally come from cyanobacteria that were “hijacked” by a host cell in the course of evolution and absorbed into the interior of the cell. Because of this history of origin, they are surrounded by a double envelope membrane and still have their own genome. Scientists led by Professor Hans-Henning Kunz from the LMU Biozentrum have now shown for the first time that ion transport proteins in the chloroplast membrane are involved in the regulation of these genes and thus play an important role in the control of photosynthesis.

An inner membrane in the chloroplast is the actual place of photosynthesis. However, it is surrounded by the inner envelope membrane, which, among other things, houses ion transport proteins that are responsible for regulating the ion balance in the so-called stroma. The stroma is the plasmatic basic substance inside the organelle, in which both the DNA of the chloroplast and its protein factories – the ribosomes – are located. For photosynthesis to proceed correctly, it is essential that the genes in the cell nucleus and in the chloroplasts work in a coordinated manner. “In the model plant Arabidopsis thaliana , we have now been able to demonstrate that the ion balance in the stroma influences this communication,” says Kunz.

The biologist had previously observed that chloroplast development is delayed and the plant takes care when the genes for two ion transport proteins are switched off. “Our experiments have now shown that helper proteins encoded in the cell nucleus without these ion transporters have difficulty binding their partner RNA in the chloroplast,” says Kunz. This prevents so-called RNA maturation, an important intermediate step in the transmission of the information contained in the chloroplast genes to the ribosomes. This defect was particularly pronounced in the RNA from which the ribosomes of the chloroplast are built. “Correspondingly, there are fewer functioning ribosomes, which severely impaired protein synthesis in the mutants,” says Kunz.

According to the scientists, their new findings can help protect photosynthesis more efficiently in difficult environmental conditions and thus better adapt crops to climate change. “Ion transporters could be an important tool here,” says Kunz. “Photosynthesis is very dependent on the biochemical environment in the stroma, and these transporters have a major influence on it. Only if we understand their complex functionality and structure in detail do we have the opportunity to manipulate them and make them usable. ”
The Plant Cell 2021

Featured image: Prof. Hans-Henning Kunz in the greenhouse. | © LMU


Reference: Rachael Ann DeTar, Rouhollah Barahimipour, Nikolay Manavski, Serena Schwenkert, Ricarda Höhner, Bettina Bölter, Takehito Inaba, Jörg Meurer, Reimo Zoschke, Hans-Henning Kunz, Loss of inner-envelope K+/H+ exchangers impairs plastid rRNA maturation and gene expression, The Plant Cell, 2021;, koab123, https://doi.org/10.1093/plcell/koab123


Provided by LMU Munchen

Mystery of Photosynthetic Algae Evolution Finally Solved (Botany)

Scientists have identified the protein that was the missing evolutionary link between two ancient algae species – red algae and cryptophytes.

An evolutionary mystery that had eluded molecular biologists for decades may never have been solved if it weren’t for the COVID-19 pandemic.

“Being stuck at home was a blessing in disguise, as there were no experiments that could be done. We just had our computers and lots of time,” says Professor Paul Curmi, a structural biologist and molecular biophysicist with UNSW Sydney.

Prof. Curmi is referring to research published this month in Nature Communications that details the painstaking unravelling and reconstruction of a key protein in a single-celled, photosynthetic organism called a cryptophyte, a type of algae that evolved over a billion years ago.

Up until now, how cryptophytes acquired the proteins used to capture and funnel sunlight to be used by the cell had molecular biologists scratching their heads. They already knew that the protein was part of a sort of antenna that the organism used to convert sunlight into energy. They also knew that the cryptophyte had inherited some antenna components from its photosynthetic ancestors – red algae, and before that cyanobacteria, one of the earliest lifeforms on earth that are responsible for stromatolites.

But how the protein structures fit together in the cryptophyte’s own, novel antenna structure remained a mystery – until Prof. Curmi, PhD student Harry Rathbone and colleagues from University of Queensland and University of British Columbia pored over the electron microscope images of the antenna protein from a progenitor red algal organism made public by Chinese researchers in March 2020.

Unravelling the mystery meant the team could finally tell the story of how this protein had enabled these ancient single-celled organisms to thrive in the most inhospitable conditions – metres under water with very little direct sunlight to convert into energy.

A cryogenic electron microscopy map of a cryptophyte-like protein found in red algae. The red indicates the elusive protein that was re-used by cryptophytes in their own antenna. Picture: UNSW

Prof. Curmi says the major implications of the work are for evolutionary biology.

“We provide a direct link between two very different antenna systems and open the door for discovering exactly how one system evolved into a different system – where both appear to be very efficient in capturing light,” he says.

“Photosynthetic algae have many different antenna systems which have the property of being able to capture every available light photon and transferring it to a photosystem protein that converts the light energy to chemical energy.”

By working to understand the algal systems, the scientists hope to uncover the fundamental physical principles that underlie the exquisite photon efficiency of these photosynthetic systems.  Prof. Curmi says these may one day have application in optical devices including solar energy systems.

Eating for two

To better appreciate the significance of the protein discovery, it helps to understand the very strange world of single-celled organisms which take the adage “you are what you eat” to a new level.

As study lead author, PhD student Harry Rathbone explains, when a single-celled organism swallows another, it can enter a relationship of endosymbiosis, where one organism lives inside the other and the two become inseparable.

“Often with algae, they’ll go and find some lunch – another alga – and they’ll decide not to digest it. They’ll keep it to do its bidding, essentially,” Mr Rathbone says. “And those new organisms can be swallowed by other organisms in the same way, sort of like a matryoshka doll.”

In fact, this is likely what happened when about one and a half billion years ago, a cyanobacterium was swallowed by another single-celled organism. The cyanobacteria already had a sophisticated antenna of proteins that trapped every photon of light. But instead of digesting the cyanobacterium, the host organism effectively stripped it for parts – retaining the antenna protein structure that the new organism – the red algae – used for energy.

And when another organism swallowed a red alga to become the first cryptophyte, it was a similar story. Except this time the antenna was brought to the other side of the membrane of the host organism and completely remoulded into new protein shapes that were equally as efficient at trapping sunlight photons.

Evolution

As Prof. Curmi explains, these were the first tiny steps towards the evolution of modern plants and other photosynthetic organisms such as seaweeds.

“In going from cyanobacteria that are photosynthetic, to everything else on the planet that is photosynthetic, some ancient ancestor gobbled up a cyanobacteria which then became the cell’s chloroplast that converts sunlight into chemical energy.

“And the deal between the organisms is sort of like, I’ll keep you safe as long as you do photosynthesis and give me energy.”

One of the collaborators on this project, Dr Beverley Green, Professor Emerita with the University of British Columbia’s Department of Botany says Prof. Curmi was able to make the discovery by approaching the problem from a different angle.

“Paul’s novel approach was to search for ancestral proteins on the basis of shape rather than similarity in amino acid sequence,” she says.

“By searching the 3D structures of two red algal multi-protein complexes for segments of protein that folded in the same way as the cryptophyte protein, he was able to find the missing puzzle piece.”

Featured image: A computer model of the novel protein structure in the cryptophyte’s antenna that traps sunlight energy. Picture: UNSW


Reference: Rathbone, H.W., Michie, K.A., Landsberg, M.J. et al. Scaffolding proteins guide the evolution of algal light harvesting antennas. Nat Commun 12, 1890 (2021). https://doi.org/10.1038/s41467-021-22128-w https://www.nature.com/articles/s41467-021-22128-w


Provided by UNSW

Photosynthesis Could Be As Old As Life Itself (Botany)

Researchers find that the earliest bacteria had the tools to perform a crucial step in photosynthesis, changing how we think life evolved on Earth.

The finding also challenges expectations for how life might have evolved on other planets. The evolution of photosynthesis that produces oxygen is thought to be the key factor in the eventual emergence of complex life. This was thought to take several billion years to evolve, but if in fact the earliest life could do it, then other planets may have evolved complex life much earlier than previously thought.

“Now, we know that Photosystem II shows patterns of evolution that are usually only attributed to the oldest known enzymes, which were crucial for life itself to evolve.”

— Dr Tanai Cardona

The research team, led by scientists from Imperial College London, traced the evolution of key proteins needed for photosynthesis back to possibly the origin of bacterial life on Earth. Their results are published and freely accessible in BBA – Bioenergetics.

Lead researcher Dr Tanai Cardona, from the Department of Life Sciences at Imperial, said: “We had previously shown that the biological system for performing oxygen-production, known as Photosystem II, was extremely old, but until now we hadn’t been able to place it on the timeline of life’s history.

“Now, we know that Photosystem II shows patterns of evolution that are usually only attributed to the oldest known enzymes, which were crucial for life itself to evolve.”

Early oxygen production

Photosynthesis, which converts sunlight into energy, can come in two forms: one that produces oxygen, and one that doesn’t. The oxygen-producing form is usually assumed to have evolved later, particularly with the emergence of cyanobacteria, or blue-green algae, around 2.5 billion years ago.

While some research has suggested pockets of oxygen-producing (oxygenic) photosynthesis may have been around before this, it was still considered to be an innovation that took at least a couple of billion years to evolve on Earth.

The new research finds that enzymes capable of performing the key process in oxygenic photosynthesis – splitting water into hydrogen and oxygen – could actually have been present in some of the earliest bacteria. The earliest evidence for life on Earth is over 3.4 billion years old and some studies have suggested that the earliest life could well be older than 4.0 billion years old.

Colonies of cyanobacteria under the microscope ©  Ye.Maltsev/Shutterstock

Like the evolution of the eye, the first version of oxygenic photosynthesis may have been very simple and inefficient; as the earliest eyes sensed only light, the earliest photosynthesis may have been very inefficient and slow.

On Earth, it took more than a billion years for bacteria to perfect the process leading to the evolution of cyanobacteria, and two billion years more for animals and plants to conquer the land. However, that oxygen production was present at all so early on means in other environments, such as on other planets, the transition to complex life could have taken much less time.

Measuring molecular clocks

The team made their discovery by tracing the ‘molecular clock’ of key photosynthesis proteins responsible for splitting water. This method estimates the rate of evolution of proteins by looking at the time between known evolutionary moments, such as the emergence of different groups of cyanobacteria or land plants, which carry a version of these proteins today. The calculated rate of evolution is then extended back in time, to see when the proteins first evolved.

“We could develop photosystems that could carry out complex new green and sustainable chemical reactions entirely powered by light.”

— Dr Tanai Cardona

They compared the evolution rate of these photosynthesis proteins to that of other key proteins in the evolution of life, including those that form energy storage molecules in the body and those that translate DNA sequences into RNA, which is thought to have originated before the ancestor of all cellular life on Earth. They also compared the rate to events known to have occurred more recently, when life was already varied and cyanobacteria had appeared.

The photosynthesis proteins showed nearly identical patterns of evolution to the oldest enzymes, stretching far back in time, suggesting they evolved in a similar way.

First author of the study Thomas Oliver, from the Department of Life Sciences at Imperial, said: “We used a technique called Ancestral Sequence Reconstruction to predict the protein sequences of ancestral photosynthetic proteins.

“These sequences give us information about how the ancestral Photosystem II would have worked and we were able to show that many of the key components required for oxygen evolution in Photosystem II can be traced to the earliest stages in the evolution of the enzyme.”

Directing evolution

Knowing how these key photosynthesis proteins evolve is not only relevant for the search for life on other planets, but could also help researchers find strategies to use photosynthesis in new ways through synthetic biology.

Dr Cardona, who is leading such a project as part of his UKRI Future Leaders Fellowship, said: “Now we have a good sense of how photosynthesis proteins evolve, adapting to a changing world, we can use ‘directed evolution’ to learn how to change them to produce new kinds of chemistry.

“We could develop photosystems that could carry out complex new green and sustainable chemical reactions entirely powered by light.”

Top image: Cyanobacteria on a water surface © Kletr/Shutterstock


Reference: ‘Time-resolved comparative molecular evolution of oxygenic photosynthesis’ by Thomas Oliver, Patricia Sanchez-Baracaldo, Anthony W. Larkum, A. William Rutherford, and Tanai Cardona is published in BBA – Bioenergetics.


Provided by Imperial College London

The Hidden Machinery of a Photosynthetic Giant Revealed (Botany)

A team of international researchers from Osaka University in Japan and Ruhr-Universität Bochum (RUB) solved the structure of monomeric photosystem I by cryo-electron microscopy.

Photosynthesis is the fundament of almost all live on earth, and yet it is not understood down to the last detail. An international research team has now unravelled one of its secrets. The researchers from Ruhr-Universität Bochum (RUB), Osaka University, Japan, and Kafrelsheikh University, Egypt, have successfully isolated a rare manifestation of photosystem I and studied it in detail. The study provided new insights into the transport of light-energy in this giant photosynthetic protein complex. The collaborative work is published online in the journal “Communications Biology” on March 8th, 2021.

The power of photosynthesis

Photosynthesis represents the only biological process, which converts the energy of sunlight into chemically stored energy. On molecular level, the photosynthetic key enzymes called photosystems are responsible for this conversion process. Photosystem I (PSI), one of the two photosystems, is a large membrane protein complex that can be present in different forms – as monomers, dimers, trimers or even tetramers.

New isolation technique helps revealing the structure of monomeric PSI

Although the structure of trimeric PSI from the thermophilic cyanobacterium Thermosynechococcus elongatus was solved 20 years ago, it was not yet possible to obtain the corresponding structure of monomeric PSI. Major bottleneck was the low natural abundance of this specific PSI form. Therefore, a new extraction method was developed by the researchers at RUB, which enabled selective isolation of PSI monomers with high yield. The isolated protein complex was characterized in detail at RUB by mass-spectrometry, spectroscopy and biochemical methods, whereas the research team at Osaka University was able to solve its structure by cryo-electron microscopy.

Teamwork between chlorophylls and lipids might enable uphill energy transfer

The atomic structure of monomeric PSI provides novel insights into the energy transfer inside the protein complex as well as on the localization of so-called red chlorophylls – specially arranged chlorophylls, closely interacting with each other and thus enabling the absorption of low-energy far red light, which normally cannot be used for photosynthesis. Interestingly, the structure revealed that the red chlorophylls seem to interact with lipids of the surrounding membrane. This structural arrangement might indicate that additional thermal energy is used to make far red light accessible for photosynthesis.

Long-run cooperation bears further fruits

The collective research was carried out in the framework of the International Joint Research Promotion Program 824, a cooperation agreement between the Faculty of Biology and Biotechnology at RUB and the Institute of Protein Research (IPR) at Osaka University, established in 2017. The Promotion Program further consolidated the active, long-term collaboration between the Laboratory of Professor Genji Kurisu at IPR and the Bochum project group “Molecular Mechanisms of Photosynthesis” headed by Professor Marc Nowaczyk.

A recently established LabExchange program at the Faculty of Biology and Biotechnology with Osaka University gives RUB students additional possibilities to perform their research projects in the land of the rising sun.

Funding

The research was funded by the German Research Foundation within the framework of GRK 2341 (Microbial Substrate Conversion), by the Platform Project for Supporting Drug Discovery and Life Science Research (BINDS) from AMED, a Grants-in-Aid for Scientific Research from MEXT-KAKENHI, the Cyclic Innovation for Clinical Empowerment from AMED, and the International Joint Research Promotion Program from Osaka University.

Featured image: Marc Nowaczyk and Anna Frank (right) explore photosynthesis. © RUB, Marquard


Reference: Orkun Çoruh, Anna Frank, Hideaki Tanaka, Akihiro Kawamoto, Eithar El-Mohsnawy, Takayuki Kato, Keiichi Namba, Christoph Gerle, Marc M. Nowaczyk, Genji Kurisu: Cryo-EM structure of a functional monomeric Photosystem I from Thermosynechococcus elongatus reveals ‘red’ chlorophyll cluster, in: Communications Biology, 2021, DOI: 10.1038/s42003-021-01808-9


Provided by RUB

Scientists Discovery Ends Long-standing Photosynthesis Controversy (Botany)

New findings overturn conventional thinking about the location of a key plant enzyme involved in photosynthesis

Scientists have pinpointed the location of an essential enzyme in plant cells involved in photosynthesis, according to a study published today in eLife.

The findings overturn conventional thinking about where the enzyme resides in plant cells and suggest a probable role in regulating energy processes as plants adapt from dark to light conditions.

During photosynthesis, plants convert carbon into energy stores through ‘electron transport’, involving an enzyme called ferredoxin:NADP(H) oxidoreductase, or FNR.

Plants can switch rapidly between two types of electron transport – linear electron flow (LEF) and cyclic electron flow (CEF) in response to environmental conditions. The transfer of FNR between membrane structures in the chloroplast, where photosynthesis takes place, has been linked to this switch.

“Current dogma states that FNR carries out its function in the soluble compartment of the chloroplast, but evidence suggests that the activity of FNR increases when it is attached to an internal membrane,” explains first author Manuela Kramer, a PhD student at the School of Biological and Chemical Sciences, Queen Mary University of London, UK. “We needed to find out precisely where FNR is located in the chloroplast, how it interacts with other proteins, and how this affects its activity in order to understand its role in switching between electron transport processes.”

The researchers used immuno-gold staining to pinpoint FNR in more than 300 chloroplasts from 18 individual Arabidopsis plants. The staining density of FNR was five times higher in the internal membrane system of the chloroplast (thylakoids) than in the soluble compartment (stroma), where it did not rise above background levels. This significantly higher labelling in the membrane proved that chloroplasts contain little soluble FNR, and confirmed for the first time where the enzyme is located.

To understand more about FNR’s location, the team generated plants where the enzyme is specifically bound to different proteins called ‘tether proteins’. In Arabidopsis plants with decreased FNR content, they substituted three versions of FNR from maize, each with a different capacity for binding to the tether proteins TROL and Tic62. They found that rescue with maize FNR types that strongly bound to the Tic62 tether protein resulted in much higher density of gold FNR labelling in specific, lamellar membrane regions of the thylakoids. This suggests that the distribution of FNR throughout the chloroplast in plant cells is dependent on binding to the tether proteins.

Finally, the team tested how FNR location affects electron transport, by comparing electron flow rates when plants were adapted to the dark with electron flow after their acclimatisation to light. In normal dark-adapted plants, a short exposure to light resulted in a switch to higher CEF activity. However, this was not seen in plants lacking strong interaction between FNR and the tether proteins, suggesting these plants lack the ability to switch on CEF. After light acclimatisation, both the wild-type and mutant plants had similar, decreased CEF activity, suggesting that the impact of FNR is related to light-dependent changes in the interactions between the enzyme and tether proteins.

“Our results show a link between the interaction of FNR with different proteins and the activity of an alternative photosynthetic electron transport pathway,” concludes senior author Guy Hanke, Senior Lecturer in Plant Cell and Molecular Biology at the School of Biological and Chemical Sciences, Queen Mary University of London. “This supports a role for FNR location in regulating photosynthetic electron flow during the transition of plants from dark to light.”


Reference:

  1. Plant Biology

Regulation of photosynthetic electron flow on dark to light transition by Ferredoxin:NADP(H) Oxidoreductase interactions“, Manuela Kramer et al. Research Article  Mar 9, 2021.


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