Plants save energy when absorbing potassium

University of Würzburg

 

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Plants have two separate potassium uptake systems, the transporter HAK5 and the channel AKT1. Depending on the potassium concentration in the soil, one or the other system is responsible for the uptake of potassium into the roots. This ensures a constant supply of potassium even when potassium availability varies.

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Credit: Tobias Maierhofer / University of Wuerzburg

Potassium is one of the nutrients that plants need in large quantities. However, the amount of potassium in the soil can vary greatly: potassium-poor soils can contain up to a thousand times less of this nutrient than potassium-rich soils. To be able to react flexibly to these differences, plants have developed mechanisms with which they adapt their potassium uptake to the respective soil condition.

Like the cells of the human body, plant cells also work with an operating potassium concentration of around 100 millimolar. If the roots find a potassium source with a significantly lower concentration or only traces of it, they can only absorb the potassium into their cells by expending energy. This is achieved by the interaction between the potassium ion channel AKT1 and the potassium transporter HAK5.

Research is Relevant for Plant Breeding

‘Although HAK5 has been known since the late 1990s, its transport mechanism has so far remained largely unknown,’ says Professor Rainer Hedrich from Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany. A team led by the Würzburg biophysicist now wanted to elucidate this mechanism: ‘Knowledge about this is important when it comes to breeding crops that also produce yields on non-fertilised or only lightly fertilised fields, i.e. that can manage with less fertiliser.’

In their experiments, the Würzburg research group led by first authors Tobias Maierhofer and Sönke Scherzer benefited from their extensive experience with the potassium channel AKT1. The group now describes their results in detail in the journal Nature Communications.

Establishing a pH Gradient Costs Energy

For the AKT1 channel to transport potassium into the cells, higher soil potassium concentrations are required. The normal electric field of the cell membrane is sufficient as an energy source. The HAK5 transporter, on the other hand, already works at low soil potassium levels. In addition to the electric field, it needs the energy of the pH gradient. The plant must build up this gradient across the cell membranes, and this costs energy.

Further experiments showed that the potassium transporter HAK5 and the potassium channel AKT1 co-operate in an energy-saving manner when the potassium concentration in the soil fluctuates.

Transporter Must Have a Potassium Sensor

At high concentrations, the energy-guzzling transporter HAK5 is switched off. This means that the transporter must have a potassium sensor. In their search for the sensor, the Frankfurt structural biologist Inga Hänelt and her Würzburg colleague Thomas Müller made progress: they found a mutant of the transporter in which the affinity for potassium is 100 times lower.

‘Now it is important to explore in more detail the molecular reactions that trigger the mutation,’ says Rainer Hedrich, describing the next research goals. He also wants to find out how potassium transport into the root cell is mechanically and energetically coupled to proton transport.

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Journal

Nature Communications

DOI

10.1038/s41467-024-52963-6 

Method of Research

Experimental study

Subject of Research

Cells

Article Title

Arabidopsis HAK5 under low K+ availability operates as PMF powered high-affinity K+ transporter

 

Galápagos finches could be singing a different song after repeated drought—one that leads to speciation

Summary author: Becky Ham

American Association for the Advancement of Science (AAAS)

Galápagos finches use their beaks to crush seeds and sing songs, so what happens to their musical trills when their beaks change to respond to new menus available under drought? Jeffrey Podos and Katie Schroeder found that the song might not remain the same after six cumulative future drought events that would likely reshape the finch beak. The projected changes in male mating songs could be so significant that they provide a pathway for ecological speciation, the researchers suggest. The researchers tested this idea by digitally modifying male mating songs of Darwin’s medium ground finches (Geospiza fortis) to sound like they might if beaks grew bigger under one, three or six cumulative future drought events. They then tested these “ghost of finches future” songs by playing them back to today’s male finches, as if the singers of the ghost songs were intruding on the males’ territory. Current males did not show signs of recognizing songs produced after six cumulative future drought events, treating the unseen producers of these songs as if they were no longer mating rivals. The study provides a better idea of how much “ecological change, and matched evolution of beaks and songs, would be required to elevate barriers to reproductive isolation,” the researchers write.

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Journal

Science

DOI

10.1126/science.adj4478 

Article Title

Ecological speciation in Darwin’s finches: Ghosts of finches future

Article Publication Date

11-Oct-2024

How playing songs to Darwin’s finches helped UMass Amherst biologists confirm link between environment and the emergence of new species

Long-term scientific effort to empirically link evolution to environmental change succeeds thanks to songs from future finches

University of Massachusetts Amherst

 

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The beaks of Darwin's medium ground finches can evolve to crush the shells of hard seeds.

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Credit: Andrew Hendry

AMHERST, Mass. – They say that hindsight is 20/20, and though the theory of ecological speciation — which holds that new species emerge in response to ecological changes — seems to hold in retrospect, it has been difficult to demonstrate experimentally, until now. In research recently published in Science, biologists from the University of Massachusetts Amherst have identified a key connection between ecology and speciation in Darwin’s finches, famous residents of the Galápagos Islands, Ecuador. Prior work on these birds had established that birds’ beaks adapt to changing ecological environments, and that beak changes affect how the birds sing. But, until this paper, no one has yet been able to experimentally show that such changes drive the emergence of new species. The innovative key to this discovery? The ghosts of future finches.

Research recently published in Science by biologists from UMass has identified a connection between ecology and speciation in Darwin’s finches, famous residents of the Galápagos Islands, Ecuador. Prior work on these birds had established that birds’ beaks adapt to changing ecological environments, and that beak changes impact how the birds sing. The new study shows that beak-driven changes to song themselves can impact species recognition, and thus drive the separation of species.

“I started working with these birds 25 years ago,” says Jeffrey Podos, professor of biology at UMass Amherst and the paper’s senior author. “In my very first publication on the finches, back in 2001, I showed that changes in the beaks of Darwin’s finches leads to changes in the songs they sing, and I speculated that, because Darwin’s finches use songs to attract mates, then song changes related to beak evolution could perhaps catalyze ecological speciation.”

But, at the time, Podos had no smoking-gun experimental evidence with which to prove his hypothesis that environmentally driven changes to beak shapes were driving the emergence of new finch species. Part of the difficulty is that speciation is an historical process, which makes it tricky to document.  Being able to watch it unfold as it happens would be like catching lightning in a bottle. As a workaround, Podos devised an experimental study that built on simulations, and he had some helpful leads to work with.

He knew, for instance, that beaks can either evolve powerfully to crush hard seeds or they can remain more delicate thereby enabling the faster movements necessary for more elaborate singing. “It takes serious motor performance to sing an intricate song, like that of the swamp sparrow,” says Podos, “and a big, powerful beak is just too clunky to manage the movements required.”

Thanks to decades’ worth of quantitative research that the wider biology community has conducted on the exact changes that the beaks of Darwin’s finches undergo due to different environmental changes, Podos realized that he could model how beaks would change into the future. In this case, he chose drought as the ecological driver, which tends to select for thicker-beaked finches. And he also knew that he could both predict, and then simulate, the songs of the finches as they would change through successive future episodes of drought.

“Essentially, we engineered the calls of future finches,” says Podos.

In general, the thicker the beak, the slower the songs and the narrower the bandwidth of the frequencies. Each subsequent drought event is predicted to render beaks that are increasingly thicker, which further should further slow the rate and decrease the bandwidths of the songs.

Finally, Podos and his team returned to the specific population of Darwin’s medium ground finches and played them the calls of the future finches.

“We found that there were no changes in the finches’ responses to our modified calls even when the simulated songs had changed by the equivalent of three drought events,” says Katie M. Schroeder, the paper’s co-author who participated in this research during her doctoral training under Podos at UMass Amherst. “But by six drought events, the had changed so much that the finches barely responded at all.”

These findings suggest that, because of the links between beaks and song, an entirely new species of Darwin’s medium ground finches could evolve in response to six major Galápagos droughts.

“Our research is not a conceptual revolution,” says Podos, “but it is an empirical, experimental confirmation of ecological speciation and its plausibility.”

This research was supported by the Charles Darwin Research Station and Galápagos National Park Service and the U.S. National Science Foundation.

 

Science has prepared a media kit, which is available at https://www.eurekalert.org/press/scipak/.

Additional images and audio recordings are available at this Google Drive link.

 

The mating song of a male Darwin's medium ground finch. (AUDIO)

Caption

The mating song of a male Darwin's medium ground finch.

Credit

Jeff Podos

How drought drives speciation 

Each drought event should increase the beak depth, which should in turn drive changes to the Darwin's medium ground finch song (l). The right panel gives a graphical representation of simulated beak changes and a spectrogram showing the corresponding projected changes in vocal performance.

Credit

Podos et al. 2024.

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Journal

Science

DOI

10.1126/science.adj4478 

Article Title

Ecological Speciation in Darwin’s Finches: Ghosts of Finches Future

Article Publication Date

10-Oct-2024

 

From chaos to structure

How a bunch of seemingly disorganized cells go on to form a robust embryo

Peer-Reviewed Publication

Institute of Science and Technology Austria

 

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The ISTA professor and theoretical physicist investigates how cells behave at the right place and time during embryo development.

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Credit: Nadine Poncioni/ISTA

Pipetting liquids into tiny test tubes, analyzing huge datasets, poring over research publications—all these tasks are part of being a scientist. But breaking this routine is essential. Time away from the usual work environment can spark creative ideas. Lab retreats, for instance, offer a great setting where researchers can engage with other peers, often leading to new collaborations.

The latter was true for Bernat Corominas-Murtra and Edouard Hannezo from the Institute of Science and Technology Austria (ISTA). Fascinated by a dataset showcased during a poster session at a collaborative retreat research group in Spain, Corominas-Murtra started a lively discussion with fellow researcher Dimitri Fabrèges, a postdoc from the research group of Professor Takashi Hiiragi at the Hubrecht Institute in Utrecht, The Netherlands. What started as a conversation has now turned into a publication in Science.

The international team of researchers has built a comprehensive atlas of early mammalian morphogenesis—the process of an organism developing shape and structure—analyzing how mouse, rabbit, and monkey embryos develop in space and time. Based on this atlas, they see that individual events such as cell divisions and movements are highly chaotic, yet the embryos as a whole end up looking very similar to one another. With this dataset, they propose a physical model that explains how a mammalian embryo builds structure from chaos.

From one to many

In animals, embryonic development starts when an egg cell is fertilized. This event triggers an array of consecutive cell divisions, known as cleavages. In a nutshell, a single cell divides into two, then two become four, four become eight, and so forth. Eventually, the bulk of cells form into a very organized structure called the blastocyst, from which all future organs and tissues develop. The entire process is termed morphogenesis.

“These early steps of embryonic development are key, as they set the stage for all subsequent developmental processes,” explains Edouard Hannezo. In some animals, for instance, in C. elegans—a transparent roundworm and one of the most studied model organisms by developmental biologists—the divisions in the early embryo are extremely well regulated and orientated the same way across different embryos, giving rise to organisms that all have the same number of cells. In mammalian species, however, it seems like divisions are much more random, both in timing and orientation. This raises the question of how reproducible mammalian embryonic development proceeds despite this disorder.

A detailed embryo map

To address this question, the Hiiragi group set out to image and quantitatively analyze many different embryos, to compare their similarities both within and between different mammalian species, from mice to rabbits and monkeys. Dimitri Fabrèges and colleagues created a so-called ‘morphomap’—a map to visualize high-dimensional morphological data. “It’s an imaging analysis pipeline showing how embryos behave in time and space—a precise atlas of an embryo’s morphogenesis,” explains Hannezo.

The map allowed the scientists to quantitatively analyze the developmental process by addressing questions such as the inter-embryo variability of development. With this dataset, the scientists were able to define what ‘normal’ morphogenesis looks like.

Fabrèges presented the morphomap at the lab retreat in Spain. The data showed that the first divisions after fertilization were not regulated across mice, rabbits, and monkeys. The cells divided randomly until they reached the 8-cell stage, a stage where all embryos suddenly started to look the same. “After looking very different in the first stages, embryos seemed to converge toward each other’s shape at the end of the 8-cell stage,” Hannezo continues. But how come? What brings structure to this chaos?

An embryonal Rubik’s cube—cell cluster optimizes its packing

Corominas-Murtra and Hannezo, both theoretical physicists, were fascinated by this dataset and set out to understand this process from a theoretical standpoint.

However, an embryo’s shape is highly complex, making it difficult to determine what it means for two embryos to be similar or different. The scientists discovered that they could effectively approximate the full complexity of the structure of an embryo simply by studying the configurations of the cell-to-cell contacts. “We think that we can derive most of the important details about the morphology of an embryo by understanding the arrangements of cells or knowing which cells are physically connected—similar to connections in a social network. This approach significantly simplifies data analysis and comparisons between different embryos,” says Corominas-Murtra.

Using this information, the scientists created a simple physical model for how embryos converge to a reproducible shape. The model shows that physical laws drive embryos to form a specific morphology shared among mammals.

By destabilizing most cell arrangements except a few selective ones that lower the surface energy of the embryo, physical interactions between cells can guide the formation toward a defined shape. In other words, cells tend to stick more and more together and this seemingly simple process actually drives the embryo through successive rearrangements to the most optimal packing. It’s like embryos solve their own Rubik’s cube.

No chaos, no structure

The results provide a detailed look at how the development of mammalian embryos is governed by variability and robustness. Without chaos, there is no structure; one needs the other. Both are essential parts of what constitutes ‘normal’ development. “We’re finally starting to have tools to analyze the variability of morphogenesis, which is crucial to understanding the mechanisms of developmental robustness,” Hannezo summarizes. Randomness seems to be a primary force in the generation of complexity in the living world.

By gaining more knowledge of what normal looks like, scientists also gain insights into abnormalities. This can be very helpful in areas, such as disease research, regenerative medicine, or fertility treatments. In the future, this knowledge can assist in selecting the healthiest embryo for in vitro fertilization (IVF), thereby improving the implantation success rate.

The schematic shows that the 4-cell stage embryo gives rise to many different shapes. At the beginning of the 8-cell stage, the embryos are driven toward the most optimal packing due to simple physical laws.

Credit

Fabrèges & Corominas Murtra et al. / Science

Journal

Science

DOI

10.1126/science.adh1145 

Method of Research

Computational simulation/modeling

Subject of Research

Cells

Article Title

Temporal variability and cell mechanics control robustness in mammalian embryogenesis

Article Publication Date

11-Oct-2024

 EMOTIONAL PLAGUE

New Lancet Commission calls for urgent action on self-harm across the world

University of Bristol

Self-harm remains neglected worldwide, with at least 14 million episodes yearly. A new Lancet Commission, led by University of Bristol researchers, urges policy action on societal drivers and health services’ response to this pressing issue. The report, involving an international team of experts, is published today [9 October].

Self-harm is not a psychiatric diagnosis; it is a behaviour shaped by society, culture, and individual factors. The social determinants of health, particularly poverty, heavily influence the distribution of self-harm within communities.

This new report highlights that at least 14 million episodes of self-harm occur each year[1], with the greatest burden felt in low- and middle-income countries (LMICs) and a higher incidence among young people. However, the authors suggest that this figure is likely an underestimate as people who self-harm often do not present to health services and there are few routine surveillance systems.

The authors also describe how attitudes lacking empathy, including in healthcare settings, can compound stigma around self-harm and keep people from seeking help. The report’s authors call on governments to recognise the public health impact of self-harm, and the need for mainstream and social media outlets need to report and publicise information about self-harm responsibly and sympathetically.

Paul Moran, Professor of Psychiatry and Head of the Centre for Academic Mental Health in the Bristol Medical School: Population Health Sciences (PHS) at the University of Bristol, and the Commission’s lead author said: “Self-harm signals deeper distress and affects millions globally, especially young people, yet it remains neglected due to stigma and lack of resources. This must change so that more people receive compassionate, tailored support.”

Report

‘The Lancet Commission on self-harm’ by Paul Moran, Helen Christensen et al. in The Lancet

 

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Journal

The Lancet

Method of Research

Commentary/editorial

Article Title

The Lancet Commission on self-harm

Article Publication Date

9-Oct-2024

 

Hot dragonfly summer: species with darker wings have evolved to withstand heat and attract partners

Researchers found that male dragonflies with dark coloration on their wings have evolved to tolerate higher temperatures, possibly a decisive advantage in a warming world

Frontiers

 

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Infrared-spectrum image of an ornamented dragonfly from the genus Tramea. Lighter colors indicate hotter temperatures, ranging from 27 to 35 degrees Celsius across the image. Image: Noah Leith. 

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Credit: Image: Noah Leith

Temperature determines where species can live and if they are threatened by a warming climate. So, for a long time, biologists studied how heat tolerance affects survival. Yet, less is known about how thermal traits influence reproduction, which is directly linked to extinction risk.

Now, researchers in the US have examined if males of dragonfly species that produce sexual signals in the form of dark coloration on their wings are more resistant to heat. They published their results in Frontiers in Ethology.

“We show that dragonfly species that have evolved dark breeding coloration on their wings have also evolved the ability to tolerate high temperatures,” said Dr Noah Leith, a biologist at the University of Pittsburgh. “This finding paves the way for a whole new field of research exploring interactions between thermal traits and sexual signals.”

Dark spots, hot dragonflies

In dragonflies – same as in many animals – sexual signals can help them effectively locate mates, identify the correct species to mate with, and decide when to back out of mating contests.

Producing extensive dark wing coloration, though, comes at a cost. Dark ornaments absorb extra heat, increasing dragonflies’ body temperature. This can cause physiological stress or lead to males abandoning reproductive territories. “We see time and time again that animals will put their lives on the line to reproduce, even if it means encountering potentially lethal temperatures,” Leith said.

The researchers examined the wing coloration of 14 dragonfly species living in tropical climates and five species living in temperate climates. They found that species that possess dark, heat-absorbing wing coloration have evolved to be able to withstand higher heat stress before reaching critical thermal maxima. “This enhanced ability to tolerate high body temperatures is likely crucial for shaping how dragonflies may respond to the changing climates of the future,” Leith explained.

Beat the heat

Dark wing ornaments cause additional heating of 1°C to 2°C, which roughly equals the increased thermal maxima of ornamented species. Of the species studied, the arch-tipped glider (Tauriphila argo), a tropical species with very dark wing color patches near their core body, could tolerate the highest temperatures. Generally, this pattern of co-evolution was even stronger in tropical species.

Previous research showed that due to rising temperatures worldwide, some ornamented dragonfly species are evolving reduced wing coloration. The present results, however, suggest that even if those species lose their coloration, they will still have a leg up on adaptation to climate change because they’ve already evolved to tolerate hotter temperatures, the researchers said.

Preventing extinction

The study is one of the first to test whether thermal tolerance co-evolves with reproductive traits. “Our finding is particularly exciting because dark sexual coloration has evolved over and over across the tree of life and causes a wide variety of other animals to absorb extra heat too—from reptiles, to lions, and fruit flies,” Leith pointed out.

In a rapidly warming world, being able to predict which species are vulnerable to extinction is essential to preserving biodiversity, the researchers said. “Looking at vulnerability in only one aspect of animals’ lives is insufficient. We need a more nuanced understanding of how animals respond to changing environments as whole, complex organisms, in which their reproductive traits might influence their chances of surviving a heat wave, and vice versa,” Leith said.

While the researchers noted that looking at 19 species was plenty for their analysis, they said that there are thousands of dragonfly species. Future research should examine if similar patterns exist in other species, as well as in different types of animals. “It would be fantastic to someday test if heat tolerance co-evolves with sexual traits across life on Earth,” Leith concluded.

Ornamented dragonfly 

Visible-spectrum image of a dragonfly with dark wing coloration form the genus Tramea. Image: Noah Leith.

Credit

Image: Noah Leith.

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Journal

Frontiers in Ethology

DOI

10.3389/fetho.2024.1447637 

Method of Research

Observational study

Subject of Research

Animals

Article Title

Heat-absorbing sexual coloration co-adapts with increased heat tolerance in dragonflies

Article Publication Date

10-Oct-2024