Category: 7. Science

For a decade, scientists have believed that plants sensed temperature mainly through specialized proteins, and mainly at night when the air is cool. New research suggests that during the day, another signal takes over. Sugar, produced in sunlight, helps plants detect heat and decide when to grow.

The study, led by Meng Chen, a University of California, Riverside professor of cell biology, shows that plants rely on multiple heat-sensing systems, and that sugar plays a central and previously unrecognized role in daytime temperature response. The findings, published in Nature Communications, reshape a long-standing view of how plants interact with their environment and could influence future strategies for climate-resilient agriculture.

“Our textbooks say that proteins like phytochrome B and early flowering 3 (ELF3) are the main thermosensors in plants,” Chen said. “But those models are based on nighttime data. We wanted to know what’s happening during the day, when light and temperature are both high because these are the conditions most plants actually experience.”

To investigate, the researchers used Arabidopsis, a small flowering plant favored in genetics labs. They exposed seedlings to a range of temperatures, from 12 to 27 degrees Celsius, under different light conditions, and tracked the elongation of their seedling stems, known as hypocotyls — a classic indicator of growth response to warmth.

They found that phytochrome B, a light-sensing protein, could only detect heat under low light. In bright conditions that mimic midday sunlight, its temperature-sensing function was effectively shut off. Yet, the plants still responded to heat, growing taller even when the thermosensing role of phytochrome B was greatly diminished. That, Chen said, pointed to the presence of other sensors.

One clue came from studies of a phytochrome B mutant lacking its thermosensing function. These mutant plants could respond to warmth only when grown in the light. When grown in the dark, without photosynthesis, they lacked chloroplasts and did not grow taller in response to warmth. But when researchers supplemented the growing medium with sugar, the temperature response returned.

“That’s when we realized sugar wasn’t just fueling growth,” Chen said. “It was acting like a signal, telling the plant that it’s warm.”

Further experiments showed that higher temperatures triggered the breakdown of starch stored in leaves, releasing sucrose. This sugar in turn stabilized a protein known as PIF4, a master regulator of growth. Without sucrose, PIF4 degraded quickly. With it, the protein accumulated but only became active when another sensor, ELF3, also responded to the heat by stepping aside.

“PIF4 needs two things,” Chen explained. “Sugar to stick around, and freedom from repression. Temperature helps provide both.”

The study reveals a nuanced, multi-layered system. During the day, when light is used as the energy source to fix carbon dioxide into sugar, plants also evolved a sugar-based mechanism to sense environmental changes. As temperatures rise, stored starch converts into sugar, which then enables key growth proteins to do their job.

The findings could have practical implications. As climate change drives temperature extremes, understanding how and when plants sense heat could help scientists breed crops that grow more predictably and more resiliently under stress.

“This changes how we think about thermosensing in plants,” Chen said. “It’s not just about proteins flipping on or off. It’s about energy, light, sugar, as well.”

The findings also underscore, once again, the quiet sophistication of the plant world. In the blur of photosynthesis and starch reserves, there’s a hidden intelligence. One that knows, sweetly and precisely, when it’s time to stretch toward the sky.

Cell biology is a world of constant motion and hidden structures. Much of what we know about cells comes from decades of research using microscopes, stains, and models. Yet, even in this well-charted territory, surprises still emerge – enter the “hemifusome.”

This previously unknown organelle may help explain how cells sort, recycle, and discard their internal cargo. This function is vital to life and is often disrupted in instances of genetic disease.

The discovery of this organelle, which was made by scientists at the University of Virginia and the National Institutes of Health (NIH), offers a new lens through which to study the inner workings of the cell.

It also presents a possible turning point for understanding diseases where cellular housekeeping breaks down. Using cutting-edge imaging tools, researchers have caught this organelle in action and outlined its potential impact on health and medicine.

Introducing the hemifusome

The hemifusome is not a static component but a temporary structure that appears and disappears depending on the cell’s needs.

It consists of two vesicles joined together by a partial membrane connection called a hemifusion diaphragm.

In this configuration, the vesicles do not fully merge but maintain a shared boundary that allows them to interact without blending entirely.

“This is like discovering a new recycling center inside the cell,” said researcher Seham Ebrahim, Ph.D., of UVA’s Department of Molecular Physiology and Biological Physics.

“We think the hemifusome helps manage how cells package and process material, and when this goes wrong, it may contribute to diseases that affect many systems in the body.”

These hemifused vesicles appear in two configurations. In the direct form, a smaller vesicle is attached to the outer side of a larger one, whereas in the flipped version, the smaller vesicle is embedded on the inner, or luminal, side.

In both cases, a dense particle called a proteolipid nanodroplet anchors the structure at the junction, possibly guiding its formation and stability.

How the hemifusome appears

To study hemifusomes, researchers turned to cryo-electron tomography (cryo-ET). This imaging method freezes cells rapidly, preserving them close to their natural state.

Unlike traditional electron microscopy, which can distort or destroy delicate structures, cryo-ET allows scientists to see cellular architecture as it truly exists.

By scanning the outer edges of four mammalian cell types, COS-7, HeLa, RAT-1, and NIH/3T3, the team identified hundreds of hemifusomes. These organelles made up nearly 10 percent of all membrane-bound vesicles in those regions.

Their consistency across cell types suggests they are not rare anomalies but common cellular components.

“You can think of vesicles like little delivery trucks inside the cell,” said Ebrahim, of UVA’s Center for Membrane and Cell Physiology. “The hemifusome is like a loading dock where they connect and transfer cargo. It’s a step in the process we didn’t know existed.”

What makes the hemifusome unique

Hemifusomes stand out not just for their shape, but for what’s inside them. The larger vesicle usually contains granular material, similar to what is seen in endosomes and ribosome-associated vesicles.

But the smaller vesicle shows a smooth, translucent interior. This likely reflects a protein-free or dilute aqueous solution, setting it apart from other vesicles in the cell.

The hemifusion diaphragm itself is unusually large, about 160 nanometers in diameter, far bigger than the 10 nanometer diaphragms seen in standard vesicle fusion events. These extended diaphragms appear stable, not fleeting, suggesting they may be designed to last.

In some cases, the diaphragm grows large enough to engulf the entire smaller vesicle into the larger one’s bilayer, creating a lens-like shape known in simulations as dead-end hemifusion. Seeing this in actual cells challenges the idea that such formations are purely theoretical.

Anchors and architects of the organelle

One consistent feature at the heart of hemifusomes is the dense proteolipid nanodroplet, or PND. About 42 nanometers in diameter, these droplets are lodged at the rim of the hemifusion site.

Their content, lipids and proteins, suggests they may help build or stabilize the hemifused structure.

These PNDs have never been observed in such a role before. Some appear free in the cytoplasm, others are embedded in membranes. Researchers propose that PNDs may serve as scaffolds for assembling new vesicles.

As the PND integrates into a membrane, it may kickstart the formation of the smaller vesicle seen in hemifusomes.

This process, described as de novo vesiculogenesis, stands apart from classical vesicle fusion. The presence of a unique, translucent vesicle and the absence of known docking steps indicate the hemifusome may follow its own assembly path.

Given their location and size, hemifusomes resemble some endosomal structures. To investigate this further, the researchers traced the journey of gold nanoparticles, common markers used to map endocytic activity.

The particles entered known endosomes and lysosomes but never appeared inside hemifusomes. This absence suggests that hemifusomes do not belong to the classical endocytic pathway.

Instead, they may represent a separate system operating independently of the cargo sorting carried out by proteins like ESCRT. This distinction may have wide implications for how we understand vesicle traffic inside cells.

Multivesicular bodies and disease

Some hemifusomes evolve into more complex structures. The study observed compound hemifusomes that contained multiple vesicles, all partially fused.

These could be early versions of multivesicular bodies (MVBs), which cells use to break down and recycle internal material.

In the canonical model, ESCRT proteins form inward buds that eventually pinch off inside a larger vesicle. But in hemifusomes, vesicles grow inward through hemifusion and expand with the help of PNDs.

This alternative route might explain how MVBs form in ways not covered by traditional theories.

One such condition affected by these pathways is Hermansky-Pudlak syndrome. It is a genetic disorder marked by defects in pigmentation, lung function, vision, and bleeding. Cellular recycling issues are central to the disease.

Understanding the hemifusome may help explain these disruptions and lead to future treatments.

A new model for vesicle formation

The study proposes a full model where PNDs trigger the formation of translucent vesicles that partially fuse with larger ones, forming hemifusomes.

These structures may then bud inward, transforming into flipped hemifusomes. Over time, they could scission off as free vesicles inside MVBs.

In contrast to the ESCRT system, which requires tight protein coordination, this mechanism relies on structural and biophysical cues.

It also sidesteps the need for large lipid donations from other organelles, solving a long-standing puzzle in vesicle formation research.

“This is just the beginning,” Ebrahim said. “Now that we know hemifusomes exist, we can start asking how they behave in healthy cells and what happens when things go wrong. That could lead us to new strategies for treating complex genetic diseases.”

What comes next

The implications of this discovery stretch far beyond cell biology. By offering a new pathway for how cells build and manage internal compartments, the hemifusome challenges decades of assumptions.

It also invites new thinking about disease, especially conditions where cells fail to manage their waste.

Future research will focus on identifying what proteins guide hemifusome formation and how PNDs are created.

Scientists also want to know if these structures exist in other parts of the cell, not just at the periphery. Advanced imaging tools and genetic models will be key to answering these questions.

In a field where many believed the major organelles were already mapped, the hemifusome serves as a reminder. The cell still holds secrets. And some of them could lead to cures.

The study is published in the journal Nature Communications.

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An unexpectedly strong solar storm rocked our planet on April 23, 2023, sparking auroras as far south as southern Texas in the U.S. and taking the world by surprise. 

Two days earlier, the Sun blasted a coronal mass ejection (CME) — a cloud of energetic particles, magnetic fields, and solar material — toward Earth. Space scientists took notice, expecting it could cause disruptions to Earth’s magnetic field, known as a geomagnetic storm. But the CME wasn’t especially fast or massive, and it was preceded by a relatively weak solar flare, suggesting the storm would be minor. But it became severe.

Using NASA heliophysics missions, new studies of this storm and others are helping scientists learn why some CMEs have more intense effects — and better predict the impacts of future solar eruptions on our lives.

A paper published in the Astrophysical Journal on March 31 suggests the CME’s orientation relative to Earth likely caused the April 2023 storm to become surprisingly strong.

The researchers gathered observations from five heliophysics spacecraft across the inner solar system to study the CME in detail as it emerged from the Sun and traveled to Earth.

They noticed a large coronal hole near the CME’s birthplace. Coronal holes are areas where the solar wind — a stream of particles flowing from the Sun — floods outward at higher than normal speeds.

“The fast solar wind coming from this coronal hole acted like an air current, nudging the CME away from its original straight-line path and pushing it closer to Earth’s orbital plane,” said the paper’s lead author, Evangelos Paouris of the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland. “In addition to this deflection, the CME also rotated slightly.”

Paouris says this turned the CME’s magnetic fields opposite to Earth’s magnetic field and held them there — allowing more of the Sun’s energy to pour into Earth’s environment and intensifying the storm.

Meanwhile, NASA’s GOLD (Global-scale Observations of Limb and Disk) mission revealed another unexpected consequence of the April 2023 storm at Earth.

Before, during, and after the storm, GOLD studied the temperature in the middle thermosphere, a part of Earth’s upper atmosphere about 85 to 120 miles overhead. During the storm, temperatures increased throughout GOLD’s wide field of view over the Americas. But surprisingly, after the storm, temperatures dropped about 90 to 198 degrees Fahrenheit lower than they were before the storm (from about 980 to 1,070 degrees Fahrenheit before the storm to 870 to 980 degrees Fahrenheit afterward).

“Our measurement is the first to show widespread cooling in the middle thermosphere after a strong storm,” said Xuguang Cai of the University of Colorado, Boulder, lead author of a paper about GOLD’s observations published in the journal JGR Space Physics on April 15, 2025.

The thermosphere’s temperature is important, because it affects how much drag Earth-orbiting satellites and space debris experience.

“When the thermosphere cools, it contracts and becomes less dense at satellite altitudes, reducing drag,” Cai said. “This can cause satellites and space debris to stay in orbit longer than expected, increasing the risk of collisions. Understanding how geomagnetic storms and solar activity affect Earth’s upper atmosphere helps protect technologies we all rely on — like GPS, satellites, and radio communications.”

To predict when a CME will trigger a geomagnetic storm, or be “geoeffective,” some scientists are combining observations with machine learning. A paper published last November in the journal Solar Physics describes one such approach called GeoCME.

Machine learning is a type of artificial intelligence in which a computer algorithm learns from data to identify patterns, then uses those patterns to make decisions or predictions.

Scientists trained GeoCME by giving it images from the NASA/ESA (European Space Agency) SOHO (Solar and Heliospheric Observatory) spacecraft of different CMEs that reached Earth along with SOHO images of the Sun before, during, and after each CME. They then told the model whether each CME produced a geomagnetic storm.

Then, when it was given images from three different science instruments on SOHO, the model’s predictions were highly accurate. Out of 21 geoeffective CMEs, the model correctly predicted all 21 of them; of 7 non-geoeffective ones, it correctly predicted 5 of them.

“The algorithm shows promise,” said heliophysicist Jack Ireland of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who was not involved in the study. “Understanding if a CME will be geoeffective or not can help us protect infrastructure in space and technological systems on Earth. This paper shows machine learning approaches to predicting geoeffective CMEs are feasible.”

During a severe geomagnetic storm in May 2024 — the strongest to rattle Earth in over 20 years — NASA’s STEREO (Solar Terrestrial Relations Observatory) measured the magnetic field structure of CMEs as they passed by.

When a CME headed for Earth hits a spacecraft first, that spacecraft can often measure the CME and its magnetic field directly, helping scientists determine how strong the geomagnetic storm will be at Earth. Typically, the first spacecraft to get hit are one million miles from Earth toward the Sun at a place called Lagrange Point 1 (L1), giving us only 10 to 60 minutes advanced warning.

By chance, during the May 2024 storm, when several CMEs erupted from the Sun and merged on their way to Earth, NASA’s STEREO-A spacecraft happened to be between us and the Sun, about 4 million miles closer to the Sun than L1.

A paper published March 17, 2025, in the journal Space Weather reports that if STEREO-A had served as a CME sentinel, it could have provided an accurate prediction of the resulting storm’s strength 2 hours and 34 minutes earlier than a spacecraft could at L1.

According to the paper’s lead author, Eva Weiler of the Austrian Space Weather Office in Graz, “No other Earth-directed superstorm has ever been observed by a spacecraft positioned closer to the Sun than L1.”

By Vanessa Thomas
NASA’s Goddard Space Flight Center, Greenbelt, Md.

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Octopuses can taste with their arms, and a new study reveals that specifically, they’re tasting chemical cues from microbes that grow on the surface of objects like dead crabs and living octopus eggs. These ‘flavors’, it turns out, can signal which prey is worth pursuing, or which egg isn’t going to make it.

Octopus arms bristle with neurons that inform these fascinating animals’ behaviors, sometimes even independently of their brains. Sensory receptors in their arms enable them to ‘taste by touch’, which is essential to how they decide what to nurture, what to hunt, and what isn’t worth their time.

That’s important information for these opportunistic hunters, who forage mainly at night and in shadowy crevices.

“If a microbial strain could activate a receptor, then it could generate a neural signal that tells the octopus: This is something I care about,” says Harvard University biochemist Rebecka Sepela, who led the research.

Related: Male Octopuses Stun Females With Venom to Survive Mating, Study Finds

“The microbiome is acting almost like a chemical translator. It integrates environmental signals – like changes in temperature or nutrient levels – and outputs molecules that inform the octopus how to behave.”

Proving this to be the case was an ambitious mission. The team isolated 295 different strains of bacteria from ‘biologically meaningful’ surfaces in the natural environments of wild-caught California two-spot octopuses (Octopus bimaculoides). Those meaningful surfaces included food and family: the shells of fiddler crabs (Leptuca pugilator), and egg casings of the octopus’s own offspring.

“Those microbes produce molecules that allow the octopus to tell the difference,” Sepela says. “Microbes are chemical factories. They constantly take in environmental cues and produce molecules that reflect their surroundings.”

The shells of living crabs, for instance, are surprisingly sterile, while those of decaying crabs are quickly colonized by a dense tapestry of bacteria.

Octopus egg casings tended to by a mother octopus have a curated balance of microbes, but when discarded, this is thrown off by an overgrowth of spiral-shaped bacteria.

The screening – in which Sepela’s team painstakingly tested how octopus sensory receptors reacted to each of the nearly 300 strains – revealed that just a few of these microbes, found on decaying prey or unhealthy eggs, activated the octopuses’ receptors.

To test these signals in action, octopuses who were actively brooding a clutch of eggs were given a collection of egg mimics, some marred with the spiral bacteria. The octopuses tended to these false eggs for a while, except for those bacterially marked as ‘bad eggs’, which were quickly discarded.

The researchers were even able to identify which specific molecules the octopuses responded to. This chemical ‘language’ is enabled by molecules that, despite the submarine environment, are not readily washed away from the surface on which they are formed.

While the research focuses on octopuses, Sepela and her colleagues believe this sort of chemical signaling may apply to many other kinds of microbiomes; even our own.

“This might seem like a very specific case… but what we’re seeing is actually a general rule about how organisms sense microbiomes,” says Harvard cell physiologist Nicholas Bellono.

“Across life, evolution, and organ systems, microbes are essential – and this study shows another example of how deeply they influence physiology and behavior.”

This research was published in Cell.

On the younger, black-rock islands of the Galápagos archipelago, wild-growing tomatoes are doing something peculiar. They’re shedding millions of years of evolution, reverting to a more primitive genetic state that resurrects ancient chemical defenses.

These tomatoes, which descended from South American ancestors likely brought over by birds, have quietly started making a toxic molecular cocktail that hasn’t been seen in millions of years, one that resembles compounds found in eggplant, not the modern tomato.

In a study in Nature Communications, scientists at the University of California, Riverside, describe this unexpected development as a possible case of “reverse evolution,” a term that tends to be controversial amongst evolutionary biologists.

That’s because evolution isn’t supposed to have a rewind button. It’s generally viewed as a one-way march toward adaptation, not a circular path back to traits once lost. While organisms sometimes re-acquire features similar to those of their ancestors, doing so through the exact same genetic pathways is rare and difficult to prove.

However, reversal is what these tomato plants appear to be doing.

“It’s not something we usually expect,” says Adam Jozwiak, a molecular biochemist at UC Riverside and lead author of the study. “But here it is, happening in real time, on a volcanic island.”

The key players in this chemical reversal are alkaloids. Tomatoes, potatoes, eggplants, and other nightshades all make these bitter molecules that act like built-in pesticides, deterring insect predators, fungi, and grazing animals.

While the Galápagos are famous as a place where animals have few predators, the same is not necessarily true for plants. Thus, the need to produce the alkaloids.

The researchers began this project because alkaloids in crops can be problematic. In high concentrations they are toxic to humans, hence the desire to understand their production and reduce them in the edible parts of fruits and tubers.

“Our group has been working hard to characterize the steps involved in alkaloid synthesis, so that we can try and control it,” Jozwiak says.

What makes these Galápagos tomatoes interesting isn’t just that they make alkaloids, but that they’re making the wrong ones, or at least, ones that haven’t been seen in tomatoes since their early evolutionary days.

The researchers analyzed more than 30 tomato samples collected from distinct geographic locations across the islands. They found that plants on eastern islands produced the same alkaloids found in modern cultivated tomatoes. But on western islands, the tomatoes were churning out a different version with the molecular fingerprint of eggplant relatives from millions of years ago.

That difference comes down to stereochemistry, or how atoms are arranged in three-dimensional space. Two molecules can contain exactly the same atoms but behave entirely differently depending on how those atoms are arranged.

To figure out how the tomatoes made the switch, the researchers examined the enzymes that assemble these alkaloid molecules. They discovered that changing just four amino acids in a single enzyme was enough to flip the molecule’s structure from modern to ancestral.

They proved it by synthesizing the genes coding for these enzymes in the lab and inserting them into tobacco plants, which promptly began producing the old compounds.

The pattern wasn’t random. It aligned with geography. Tomatoes on the eastern, older islands, which are more stable and biologically diverse, made modern alkaloids. Those on the younger, western islands where the landscape is more barren and the soil is less developed, had adopted the older chemistry.

The researchers suspect the environment on the newer islands may be driving the reversal.

“It could be that the ancestral molecule provides better defense in the harsher western conditions,” Jozwiak says.

To verify the direction of the change, the team did a kind of evolutionary modeling that uses modern DNA to infer the traits of long-extinct ancestors. The tomatoes on the younger islands matched what those early ancestors likely produced.

Still, calling this “reverse evolution” is bold. While the reappearance of old traits has been documented in snakes, fish, and even bacteria, it’s rarely this clear, or this chemically precise.

“Some people don’t believe in this,” Jozwiak says. “But the genetic and chemical evidence points to a return to an ancestral state. The mechanism is there. It happened.”

And this kind of change might not be limited to plants. If it can happen in tomatoes, it could theoretically happen in other species, too. “I think it could happen to humans,” he says. “It wouldn’t happen in a year or two, but over time, maybe, if environmental conditions change enough.”

Jozwiak doesn’t study humans, but the premise that evolution is more flexible than we think is serious. Traits long lost can re-emerge. Ancient genes can reawaken. And as this study suggests, life can sometimes find a way to move forward by reaching into the past.

“If you change just a few amino acids, you can get a completely different molecule,” Jozwiak says.

“That knowledge could help us engineer new medicines, design better pest resistance, or even make less toxic produce. But first, we have to understand how nature does it. This study is one step toward that.”

Source: UC Riverside

A recent study led by researchers at SapienCE has revealed that ochre—previously considered primarily a symbolic pigment—played a crucial role in the production of sophisticated stone tools by early modern humans in Blombos Cave, South Africa, during the Middle Stone Age (MSA), between 90,000 and 70,000 years ago.

While examining previously excavated artifacts at the SapienCE laboratory in Cape Town, archaeologist Elizabeth Velliky discovered an ochre fragment bearing wear patterns distinct from the typical grinding marks used for pigment production. Intrigued, she presented the artifact to colleagues Francesco d’Errico, Karen van Niekerk, and Christopher Henshilwood. Their examination confirmed the fragment had been deliberately shaped and used in a previously undescribed way. As they continued to sort through more discoveries, further ochre artifacts with the same marks appeared—seven in total—resulting in a reassessment of the use of ochre in early human life.

Published in Science Advances, the study reports the initial direct archaeological evidence that ochre was specifically crafted into retouching tools for lithic implements. Experimental research and replication studies by d’Errico and colleagues revealed that these ochre “retouchers” were used for pressure flaking and direct percussion—advanced methods in shaping stone tools. These methods are highly dexterous and mentally demanding, especially for the production of the Still Bay points: bifacial tools renowned for their symmetry and refined forms.

Notably, the ochre artifacts show signs of rejuvenation, indicating that they were maintained in good condition over time, a characteristic typical of personal or curated tools. “The sophistication of these pressure flakers implies that they were the personal property of expert toolmakers,” d’Errico said. “They may have functioned not only as practical instruments but also as indicators of identity and technical prowess.”

This discovery contradicts common assumptions that ochre’s primary role in the cultures of ancient people was symbolic—ritual, or body painting. Instead, it speaks to the pigment’s functional versatility. Earlier ethnographic and experimental studies had hinted at ochre’s use in such processes as hide tanning or hafting adhesives, but definitive archaeological evidence had remained elusive—until now.

Henshilwood, director of SapienCE, emphasized the significance of the find: “We now have evidence that ochre was not only a medium for symbolic expression but also a key material in specialized tool production, reflecting a level of technological sophistication previously associated with much later periods.”

Van Niekerk, a co-author and director of the Blombos Cave excavations, commented that this discovery adds another piece of evidence to how early Homo sapiens were behaviorally modern. “This discovery will add another layer to our understanding of the behavioral modernity of early Homo sapiens in southern Africa,” she said.