Belgium

Metabolism lies at the core of life-history theory, and the ability to adapt to fluctuating environmental conditions is key for survival and fitness. Temperature is a pervasive ecological stressor, influencing metabolic rate, development, and energy allocation. Mitochondria play a central role in temperature adaptation by regulating energy transduction and intermediary metabolism, directly impacting growth and reproduction. However, oxidative phosphorylation (OXPHOS) is uniquely vulnerable, as it depends on coordinated expression of mitochondrial (mt) and nuclear (n) genomes, which face distinct evolutionary pressures. Temperature fluctuations challenge this mitonuclear balance, exacerbating intergenomic incompatibilities. Here, I provide evidence that mitonuclear interactions shape metabolic efficiency and resource allocation in response to temperature variation in Drosophila melanogaster populations. Using coevolved and admixed mitonuclear genotypes, I show that temperature stress amplifies mitonuclear mismatches, delaying development, altering metabolism, and reducing fitness. To uncover mechanisms, I will present RNA-Seq data on mitonuclear coexpression under thermal stress, linking genomic regulation to physiological traits. Results indicate that intergenomic epistasis cascades from cellular bioenergetics to organismal performance, with climate change intensifying these incompatibilities and increasing fitness breakdown risks in hybrid populations. Understanding mitonuclear contributions to temperature adaptation is crucial for predicting evolutionary responses to climate change and identifying genetic pathways buffering metabolic stress.

SEB Conference 2025

Temperature adaptation shapes the evolutionary dynamics of mitonuclear interactions

mitochondria

drosophila

adaptation

technical paper

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Skeletal muscle performance is attributed to work producing crossbridge interactions between the contractile proteins, actin and myosin. Myosin kinetics are through to underpin the isotonic force velocity relationship observed in skeletal muscle. Variation in maximum shortening velocity (Vmax ) is attributed to variation in myosin isoform and is thought to dictate organismal performance. However, Vmax  varies in ways that cannot be explained by actin-myosin interactions, decreasing with decreasing muscle recruitment irrespective of the myosin isoform recruited. This effect of recruitment on Vmax  has been suggested to be due to the physical properties of the muscle, such as mass, viscosity and elasticity, limiting its capacity to accelerate and so reach a myosin-defined Vmax . Here we determined the effect of recruitment on Vmax  in 2 anuran plantaris muscles (cane toad and tree frog), with an ~40-fold difference in muscle mass, in vitro. If mass is an important determinant of Vmax , then we would expect a greater effect of recruitment in the larger muscle.  There was a significant effect of recruitment on Vmax  in both muscles (p< .005), and this effect was significantly greater in the larger cane toad muscle (p< .005). This has implications for the scaling of locomotor performance as the ratio between the force available for acceleration and mass to be accelerated systematically declines with increasing body size. Hence, larger species may be limited in their locomotor performance irrespective of the myosin isoform expressed, potentially explaining effects such as the scaling of maximum running speed.

The effects of muscle mass on maximum shortening velocity and the implications for scaling of locomotor performance

The radial lattice spacing (LS) of actin and myosin filaments is a fundamental determinant of muscle force generation, yet its regulation remains an open question. While the assumption of volume constancy provides a phenomenological plausibility check, it lacks a mechanistic basis for LS changes during fiber contraction. We introduce a novel model demonstrating that electrostatic repulsion between charged filaments, governed by Debye-Hückel theory, dictates LS adaptations. Under the simple assumption of energy conservation, the model predicts LS variations across sarcomere lengths with remarkable accuracy, aligning closely with experimental data and outperforming traditional volume-based models.By explaining macroscopic muscle behavior with molecular interactions, the model offers deeper insight into the physics of muscle function. The refined understanding of LS dynamics enhances predictive capabilities in musculoskeletal modeling, with implications for physiology, biomechanics, and robotics. Adaptability to different muscle types further broadens its relevance, offering potential applications in understanding pathological conditions affecting sarcomere structure or the development of targeted drugs.Providing a first-principles explanation for LS regulation, this work challenges conventional assumptions and establishes a new foundation for multi-scale muscle research, from molecular mechanisms to whole-body movement.

Filaments repel while muscles propel: A bio-physical explanation of lattice spacing

As global warming progresses, organismal pace-of-life (POL) traits evolve in response to shifting climates. A new hypothesis states that, apart from the food digestive metabolism, the mitochondrial phenotype (efficiency and density) contributes to POL-variations across thermal regimes. We investigated the thermal evolution and plasticity of the POL and its underlying mechanisms by making use of the southward range expansion of the damselfly Ischnura elegans, from France into warmer regions of Spain. Alongside the ancestral French region, we studied two Spanish regions: a ‘new edge’ region founded 10 years ago (Salamanca) and an ‘old edge’ region founded 70 years ago (Murcia-Alicante). In a common garden experiment, larvae and adults from all regions were exposed to French and Spanish summer temperatures. Our results confirmed that the old edge region evolved a faster POL than the ancestral region when exposed to Spanish temperatures. As hypothesized, the old edge individuals had higher mitochondrial and digestive efficiencies supporting their evolved fast POL. Additionally, the larvae and adults showed higher mitochondrial densities, further sustaining this pace. In contrast, the new edge region showed unexpectedly maladaptive traits, exhibiting a slower POL than the ancestral region when exposed to Spanish temperatures. These individuals increased their food intake, likely prioritizing energy allocation toward repair mechanisms to cope with thermal stress. Our findings suggest that the traditional POL framework, which links food intake to fast POL traits, may require refinement as we show for the first time that the mitochondrial phenotype is a driver of the POL during thermal evolution.

Energized and efficient: digestive efficiency and mitochondrial phenotype underlie the rapid evolution of a faster pace-of-life in a range-expanding species

Environmental temperature affects organisms’ physiology, behaviour and reproduction with costs for fitness and survival. Under climate change, extreme weather events are predicted to increase in frequency and intensity, yet it is not well known how organisms adjust to these rapid variations. Short-term fluctuating temperatures can alter an endotherms’ thermoregulatory capacity, which can be influenced by energy metabolism. On the organismal level, metabolic rate can vary with rapid temperature variations, especially outside the thermoneutral zone, and at the cellular level, mitochondrial function adjusts to meet energy demands. We investigated if repeated exposure to short-term thermal fluctuations can hinder or alleviate metabolic costs of responding to cold temperatures. To achieve this, wild great tits (Parus major) were caught in late autumn and separated into three groups: control, heatwave, and cold spell. First, all birds were kept in a controlled ambient temperature (16°C). Birds in the heatwave and cold spell groups were then subjected to three short-term temperature fluctuations (for 48 hours, 7 days apart), with temperature increasing or decreasing by 10°C from the ambient temperature. Overnight whole-body metabolic rate (basal metabolic rate and metabolic rate below thermoneutrality) and mitochondrial function were assessed at the beginning and end of the experiment. Additionally, after the first wave, daytime metabolic rate was measured below thermoneutrality to study immediate changes. The results of this study could provide insights into how animals can cope with increased climate instability, by investigating the responses to temperature fluctuations and capacity for metabolic plasticity, at both the whole-body and cellular level.

AThe impact of short-term temperature fluctuations on whole-body metabolism and mitochondrial function

How birds flap their wings, or their kinematics, vary between species, but also individual birds show variation between their wingbeats depending on the flight conditions. Understanding the aerodynamic effects of different wing kinematics can help us explain when and why birds select certain kinematics. A crucial aspect of flapping flight is the transition between successive up- and down-strokes. The pitching motion that occurs at these stages of the flapping cycle, and potential interactions between the wings, may have a large impact on the force production. This is well known for hovering flight but has not been extensively studied in forward flight.
In this presentation, we discuss experiments that were conducted using a robotic, flapping wing in a wind tunnel. The wing kinematics used different timings for the pitching motion in relation to the transition between strokes, and the flapping motion was centered around different mean elevation angles. By measuring the flow behind the wing and analyzing the obtained velocity field, we computed the aerodynamic forces produced by the flapping robot. Our results show that these understudied kinematic parameters affect the absolute and relative production of lift and thrust in flapping flight. Notably, since they have different impacts on the horizontal and vertical forces, they could explain differences in flapping strategies observed in birds at different speeds and in different conditions. The results of this research can thus contribute to understanding bird flight, but also to the design and control of flapping drones.

Aerodynamic effects of the transition between strokes in bird flight, wind tunnel study with a robotic wing

Bio-inspiration has led to the development of technical solutions by replicating principles or structures observed in living organisms to create more efficient machines. In turn, these robots can serve as scientific tools to study animal locomotion.
In this context, subterranean animals like moles exhibit a distinct morphology adapted to their specialized lifestyle. Being strictly fossorial, mole species are particularly interesting for studying burrowing performance and adaptations. Our main goal is to explore the relationship between morpho-functional patterns and burrowing performance in moles species while developing a bio-inspired project that integrates and utilizes our biological data. To deepen our understanding, we will design a bio-inspired "mole robot."
Here we present the first step in the transition between biology and mechanics, focusing on the joint level. To achieve this, we conducted anatomical dissections to accurately describe the musculoskeletal characteristics of moles. These results enabled us to precisely define the insertion zones of the muscles and joints in the forelimbs. These biological joints were then translated into mechanical counterparts to design the kinematic chain of the mole robot. Our original data provide a concrete illustration of a crucial step linking biology and robotics.

Burrowing performance in moles: a bio-inspired study from biological to mechanical joint

Predicting gene function is indispensable to our understanding of biology. However, these predictions hinge on large collections of experimentally characterized genes, the compilation of which is not only labor-intensive and time-consuming but rendered near-impossible given the volume and diversity of scientific literature. Here, we tackle this challenge by deploying the textmining capacities of Generative Pre-trained Transformer (GPT) to process over 70,000 plant biology articles. Our approach unveiled over 5,000,000 functional relationships between a wide array of biological entities—genes, metabolites, tissues, and others—with a remarkable accuracy of over 85%. We encapsulated these findings in PlantConnectome, a user-friendly database, and demonstrated its diverse utility by providing insights into gene regulatory networks, protein-protein interactions, as well as developmental and stress responses. We believe that this innovative use of AI in the life sciences will significantly accelerate and direct research, drive powerful gene function prediction methods and help us keep up to date with the rapidly growing corpus of scientific literature.

PlantConnectome: knowledge graph encompassing >70,000 plant articles

Deep Learning-Based Data Driven Yield Estimation for Capsicum Grown in Glasshouses

Anthropogenic CO2  emissions are leading to rising global temperatures and increasingly extreme weather events. High vapour pressure deficit (VPD), which often occurs during heatwaves, reduces stomatal opening, which could negate crop photosynthetic gains associated with higher atmospheric CO2  concentrations. Studying the interactive effects of increased CO2  and VPD using free-air concentration enrichment (FACE) under field conditions is challenging due to technical difficulties associated with regulating temperature and moisture content. To bypass this limitation, we conducted high-VPD (3.14 kPa) heatwave experiments on spring wheat (Triticum Aestivum) at high temperatures (37 °C) and low relative air humidity (50%) in climate-controlled growth chambers set to ambient (450 ppm) or elevated (720 ppm) CO2  concentration.
We find that elevated CO2  concentration combined with high-VPD treatment leads to higher saturating light photosynthesis and maximum rate of rubisco carboxylation (Vcmax ), but this is also associated with much greater evaporative demand than might be expected. Transpiration and thermal profiling within chambers revealed high CO2  grown plants often had higher levels of water-flux and cooler leaves than ambient CO2  equivalent plants, and overall this resulted in higher plant water usage. Light-shift assays showed that photosynthetic performance was tightly linked with stomatal performance during heatwaves at either CO2  concentration, with stomatal conductance only reducing by 37-38% during complete darkness for both CO2  treatments, which could have considerable implications for future water-use efficiency. Together, our results highlight that high CO2  and rising VPD together could aid photosynthetic performance, but this will be at the expense of higher water usage.

Saving FACE: Utilising growth chambers to study rising CO2 concentration and VPD impacts on wheat photosynthesis and water usage

Insects, as ectothermic organisms, display a remarkable ability to thrive in a wide range of thermal conditions, a key factor contributing to their success in colonizing various environments. They are thus ideal models for studying the effects of temperature on metabolic processes. Insects employ diverse strategies to survive cold winters, including entering diapause, migrating, and producing antifreeze compounds. Some insects, however, remain active throughout the winter, relying on specialized adaptations to maintain their metabolic functions. These overwintering insects, such as certain Drosophila species and eusocial honeybees, leverage a variety of physiological and cellular mechanisms to regulate their energy expenditure and sustain their cellular processes despite the challenging cold environments they inhabit. Mitochondria, as the hub of cellular metabolism, play a crucial role in these overwintering strategies. In this presentation, I will examine the mechanistic changes in mitochondrial functions, structure, and regulation that enable these insects to do so. Specifically, I will discuss the adjustments in oxygen consumption with different oxidative subtrates, reactive oxygen species metabolism, and ATP generation, as well as modifications in mitochondrial structure and ultrastructure, observed in the overwintering insects Drosophila suzukii and Apis mellifera during seasonal transitions. The understanding of these cellular and metabolic adjustments are crucial to gain valuable insights into the physiological mechanisms underlying insect cold tolerance and survival strategies.

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