Thursday, September 17, 2026

Fungi neutralize spruce defense mechanisms with sugar

A newly discovered detoxification strategy employed by fungi disarms spruce defense compounds by binding a sugar to them, which makes spruce trees more susceptible to bark beetle attacks

Max Planck Institute for Chemical Ecology

Ips typographus — image:
When bark beetles invade spruce trees, they carry various fungal species with them. These fungi multiply in the tunnels, which facilitates the beetles’ invasion.
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Credit: Benjamin Weiss, Max Planck Institute for Chemical Ecology

Well-protected chemically, but not invincible: How fungi and bark beetles penetrate spruce bark

Spruce trees have highly effective chemical defenses against herbivores and pathogens. The phloem, the living bark tissue responsible for transporting nutrients produced in the needles to the roots, is among the chemically best-protected plant tissues. The phloem lies directly beneath the protective bark and surrounds the wood. The phloem tissue contains protective chemical substances, particularly phenolic compounds, which can account for up to five percent of the bark’s dry weight. Nevertheless, numerous fungi—ranging from pathogens to symbionts of bark beetles—successfully colonize this well-defended tissue. "We wanted to understand the biochemical tricks these fungi use to overcome such a hostile chemical environment, especially since some of these fungi may contribute to massive bark beetle infestations destroying European forests," says study lead author Ruo Sun, head of the project group Metabolism of spruce tree defenses.

Fungi can metabolize spruce defense compounds

The research team investigated the metabolism of various fungi using molecular biological techniques and chemical analyses. They analyzed the metabolic products of fungi grown on real spruce bark or artificial culture media. In the process, they discovered that certain fungi produce new, previously unknown compounds—but only when exposed to the chemicals found in spruce. The scientists cultivated large quantities of these fungi, isolated the compounds, and used high-precision methods, such as nuclear magnetic resonance (NMR) spectroscopy, to determine their exact structure. Through this process, the scientists demonstrated that while some fungi break down spruce's toxic defense compounds, the resulting products remain toxic. Only two species of fungi go a step further by attaching a ribose, a simple sugar with five carbon atoms, to these degradation products. This process, known as ribosylation, reduces toxicity and prevents the toxic substances from being reactivated by the metabolism of another organism. The fungus that exhibited the strongest ribosylation ability grew best on spruce bark. This suggests that this ability provides a crucial survival advantage to the fungus.

"One of the major challenges was identifying the sugar component of the molecule as ribose and not glucose or another sugar. The analytical data showed that a pentose, or a sugar with five carbon atoms, was bound. However, based on the data, we could not distinguish between ribose, xylose, and arabinose since they all have the same molecular weight. It was only through extensive nuclear magnetic resonance (NMR) analyses that we were able to confirm the presence of ribose and its exact configuration,” said co-author Baoyu Hu, a doctoral student at the institute.

In ribosylation, the sugar molecule ribose is attached to specific molecules within the cell. This small change can have significant effects on processes such as cell-to-cell communication, DNA repair, and metabolic regulation. Compared to other sugar modifications, such as glucosylation, ribosylation has been less common and less studied. "We suspect it has been overlooked until now because most researchers assumed that detoxification involved the attachment of glucose. Identifying ribose requires chemical analyses, including NMR, to distinguish it from glucose," explains Yoko Nakamura, a research associate in the Department of Natural Product Biosynthesis who conducted the NMR analyses.

Fungal consortia as the key to overcoming spruce defense mechanisms

Not all fungi can neutralize defense compounds that contain ribose. The scientists examined twelve fungal species associated with bark beetles, including some that are not transmitted by beetles. Only two species, Coprinellus radians and Cylindrobasidium ipidophilum, exhibited this ability. This may be because ribosylation requires a great deal of energy. The fungus must "sacrifice" ribose for detoxification, which could hinder its growth. This is why this strategy is found in only a few fungal species, where it is, however, particularly effective.

Researchers have long been familiar with one of the two ribosylating fungi, Cylindrobasidium ipidophilum, found in the tunnels of bark beetles. However, the role of this symbiont remained unclear until now. The study reveals not only the ability to neutralize the spruce's defense mechanisms, but also the underlying mechanisms behind this detoxification. By neutralizing the spruce’s defense substances, it promotes the growth of other fungi associated with bark beetles. "If these fungi break down different parts of the spruce's defense system, they could collectively form a consortium that overcomes the spruce's defense mechanisms, thus holding the key to successful bark beetle colonization," says Jonathan Gershenzon, director of the Department of Biochemistry.

In future studies, the researchers plan to identify the enzyme responsible for ribosylation and determine if this ability exists in other fungal species. They also want to determine if ribosylation influences the composition of the microbiome, or the totality of microorganisms, in the bark beetles’ feeding tunnels and consequently, the beetles’ fitness. These findings could help the forestry sector develop new strategies for controlling bark beetle infestations. One possible approach would be to make specific changes to the microbial communities within spruce trees.

Journal

The ISME Journal

DOI

10.1093/ismejo/wrag230

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Fungi associated with Norway spruce and its bark beetles detoxify spruce defense compounds by conjugation to α-ribose

Article Publication Date

14-Sep-2026

Study: Why colder temps can be better for removing ice

University of Texas at Dallas

BK5A0160 — image:
University of Texas at Dallas mechanical engineering research associate Dr. Yao Ren exposes an ice-covered metal surface to dry ice to cool it further. Researchers found that a material’s thermal properties play a critical role in determining whether ice remains attached to a surface — a discovery that may lead to the design of future deicing systems for aircraft and wind turbines.
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Credit: The University of Texas at Dallas

Deicing technologies often rely on heat to melt ice. But University of Texas at Dallas researchers have found that, under extreme cold, making ice even colder can weaken its grip on surfaces.

“Our work shows that under extremely cold conditions, rapid cooling can actually make ice much easier to remove,” said Dr. Hongbing Lu, professor of mechanical engineering and the Louis Beecherl Jr. Chair in the Erik Jonsson School of Engineering and Computer Science.

The discovery, published online May 29 in the journal Newton, reveals that a material’s thermal properties play a critical role in determining whether ice remains attached to a surface. The finding could guide the design of future deicing systems for aircraft, wind turbines and other applications in extreme cold.

Lu, who directs the Mechanics of Advanced Materials Laboratory, is a co-corresponding author of the study with Dr. Xianming “Simon” Dai, associate professor of engineering technology and industrial distribution at Texas A&M University and a former associate professor of mechanical engineering at UT Dallas.

Ice accumulation on aircraft, wind turbines and power infrastructure can ground flights, reduce energy production and damage equipment. While heating can be an effective method for removing ice, supplying enough heat in very cold environments can be difficult and energy intensive.

In addition to using heat to melt ice, deicing procedures also can involve changing the chemistry of surfaces to prevent ice from sticking. Those methods, however, become less effective in extremely cold conditions, when ice still can form strong bonds with the surface.

Cracks formed in the ice on this metal sample show how rapidly cooling ice can weaken its grip on the surface in extreme-cold conditions.

UT Dallas researchers made their discovery while conducting experiments to develop ice-resistant surfaces for cold environments.

The team cooled ice on metal, glass and plastic surfaces to minus 76 degrees Fahrenheit (minus 60 degrees Celsius) to investigate whether rapid temperature changes could weaken ice adhesion. Many materials, including solid ice, contract as they get colder, but how much they change size depends on the material.

Metal and glass have similar thermal expansion properties, so researchers expected the ice to behave similarly on both surfaces. Instead, the ice released easily from the cooled metal but remained firmly attached to the glass.

At first, the result didn’t make sense.

“It puzzled us for a long time,” Lu said.

As team members looked for explanations for the unexpected behavior, they determined that the thermal conductivity of the surface played a critical role in whether the ice would detach.

In particular, the way a surface transfers heat determines the temperature change at the ice-surface interface. In general, materials that transfer heat more efficiently can cool the ice more rapidly.

“We determined that the observed behavior is the result of differences in thermal conductivity of the substrate,” Lu said. “So, simply put, the ice touching steel gets colder much faster than ice touching glass.”

Because the metal conducted heat more efficiently than glass or plastic, the ice on the metal surface cooled and contracted more than on the other surfaces. This created stresses that fractured the ice, reducing its adhesion to nearly zero.

“The ice wants to shrink more than the steel does, but because they are bonded together, the steel holds it back, putting the ice under tensile stress,” Lu said.

The study’s findings challenge conventional thinking by showing that the speed at which a surface conducts heat is an important factor in determining whether ice will detach.

“On a surface with very high thermal conductivity, we don’t want to warm the ice — we may actually want to cool it,” Lu said. “The larger temperature drop creates greater stresses in the ice, which, combined with the mismatch in how the materials contract, can cause the ice to fracture.”

The researchers developed a model that predicts how different materials will behave during rapid cooling, which could help engineers design future deicing systems.

The researchers also tested composite materials relevant to aircraft and wind turbine blades and found that carbon fiber composites, which have higher thermal conductivity than glass fiber composites, created weaker ice interfaces, making ice easier to detach.

Although additional research will be needed before the approach could be incorporated into practical deicing systems, the findings suggest that in extremely cold environments, making ice colder rather than warmer may be a better approach.

“Conventional wisdom says we need to introduce heat,” Lu said. “In some cases, however, the colder the better.”

Other UT Dallas-affiliated authors of the article were Jyotirmoy Sarma MS’18, PhD’22; Dylan Boylan PhD’25; and mechanical engineering research associate Dr. Yao Ren; from Texas A&M, postdoctoral researcher Deepak Monga PhD’24 and graduate student Meiying He contributed to the work.

Lu received funding for the research from the U.S. Department of Energy (DOE) (NA0003962, NA0003525) and the National Science Foundation (NSF) (2219347). Dai received support from the Army Research Office (W911NF1910416), DOE (EE0011217), the Defense Advanced Research Projects Agency (D23AP00160) and the NSF (2044348).

Dr. Yao Ren holds an ice-covered metal sample to demonstrate how the ice forms cracks when exposed to even colder temperatures.

Cracks formed in the ice on this metal sample show how rapidly cooling ice can weaken its grip on the surface in extreme-cold conditions.

Credit

The University of Texas at Dallas