Czechia

The stress history of an individual is predicted to impact how they handle sudden increases in environmental temperature. However, our understanding of how prior exposure to commonplace stressors, like salinity and crowding, affects ectotherm heat tolerance is lacking. We hypothesised that brief exposure to mild stress would heighten tolerance to subsequent heat stress, indicative of a cross-tolerance interaction, whereas exposure to severe stress would reduce heat tolerance, reflecting a cross-susceptibility interaction. To test this hypothesis, we assessed how three acute stressors (salinity shock, air exposure, and crowding), commonly experienced by fish, affected the heat tolerance (measured as critical thermal maximum, CTmax) of juvenile Chinook salmon (Oncorhynchus tshawytscha). Fish were exposed to one of the three stressors and left for 24 h of recovery prior to measuring CTmax. This talk will detail how the stress history (salinity shock, air exposure, or crowding) impacts the capacity to withstand a subsequent heat shock. We highlight evidence of cross-tolerance and cross-susceptibility among commonplace stressors, and detail dose-dependent effects.

SEB Conference 2024

Stress history affects heat tolerance in an aquatic ectotherm (Chinook salmon,Oncorhynchus tshawytscha)

cross protection.

ctmax

thermal tolerance

technical paper

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SEB’s Annual Conference is celebrated for creating the perfect composition of research, new discoveries and collaborative connections. Be creative and innovative by exchanging ideas and knowledge with masters of biology from all over the world.

Ammonia is a toxic nitrogenous waste causing ionoregulatory and neuronal dysfunction in aquatic animals. Ammonotelic animals excrete ammonia as is and must have therefore an efficient excretion process in place to keep blood/hemolymph ammonia levels in a tolerable range. While in fish and crustaceans, the excretory mechanism has been investigated in greater detail, the cellular regulation of these processes is rather unknown. To investigate which cellular pathways are involved in ammonia excretion, gills from osmoregulating green crabs were perfused with a hemolymph-like solution containing 500µM NH4Cl, mimicking hemolymph levels found after feeding. Activation of the PKA pathway by adding either Forskolin or 8-Bromo-cAMP, which is known to activate osmoregulatory NaCl uptake in crustaceans, to the perfusion solution caused a significant decrease in the ammonia excretion rate. By contrast, activating the PKG pathway by the addition of 8-Bromo-cGMP, caused an increase of excretion, which was blocked when PKG activity was inhibited via KT5823. When no ammonia was added to either side of the branchial epithelium, metabolic ammonia was released predominantly to the environment. Interestingly, the addition of 8-Bromo-cAMP caused not only an increase of ammoniagenesis, it also promoted that a higher proportion of metabolic ammonia is released towards the hemolymph side, while apical release remained unaltered.

The cGMP/PKG pathway, but not the cAMP/PKA pathway promotes branchial ammonia excretion in the green shore crab

The respiratory and metabolic systems of insects have been shown to exhibit developmental plasticity when exposed to alterations in oxygen availability during development. For example, adult trachea and mitochondria density in Drosophila is dependent on ambient oxygen levels experienced during larval development. Manduca sexta are large, endothermic moths that require elevated thorax temperatures for flight. Here we asked how energy demands of this endothermic insect influenced the developmental plasticity of the metabolic system under either hypoxic or hyperoxic developmental conditions. Manduca sexta were reared in either 10, 21, or 30% oxygen from the larval stage through adults. We examined the plasticity of tracheal and mitochondrial morphology and physiology of the adult moth. Hypoxic reared moths reached smaller sizes as adults while hyperoxic reared moths reached larger adult sizes compared with normoxic reared animals. Both hypoxic and hyperoxic reared moths had significantly longer pupation times than controls. Hypoxic reared moths had lower critical oxygen levels for flight compared with hyperoxic reared moths. Mitochondrial respiration rate in permeabilized flight muscle mitochondria was higher in hypoxic reared moths than in either control or hyperoxic reared moths, but this difference was not observed in isolated mitochondria. Unlike Drosophila, Manduca exhibit no developmental plasticity in mitochondrial densities or tracheal densities in response to hyperoxia and hypoxia. The developing Manduca sexta exhibits more limited plasticity in resopnse to altered oxygen when compared with other insects studied.

Are there constraints on the developmental plasticity of metabolic physiology in an endothermic insect?

Introduction: Piloerection, the phenomenon of hair standing on end, is commonly viewed as an emotional response in humans1, a perspective that potentially overlooks its broader biological significance. Unlike in other mammals where piloerection has clear functional roles, the human response has been labelled vestigial2 due to our lesser hairiness. This study challenges the notion, proposing piloerection as a complex response to environmental stimuli.
Aim and Hypothesis: We aimed to explore whether tactile, thermal, and audio-visual stimuli could trigger human piloerection, hypothesizing it as a multifunctional response to environmental changes rather than a mere emotional or vestigial reaction. We further hypothesized that piloerection influences skin temperature and is more predictably triggered by objective stimuli than by subjective emotional states or perceived coldness.

Experimental Design: We exposed participants to a variety of tactile, thermal, and audio-visual stimuli to induce piloerection. Through observing 1198 piloerection events in eight participants, we examined cardiovascular (ECG, cardiac impedance, respiration) and skin and core temperature responses to diverse stimuli, alongside participants' self-reported emotions and subjective feelings of coldness vs warmness. 

Results: Results indicated that audio-visual stimuli inducing a stronger sympathetic response and tactile stimuli inducing a parasympathetic response. Challenging its classification as vestigial, piloerection episodes were associated with changes in skin temperature (see Figure 1) and this change was stronger for more intense episodes of piloerection (B = -.98, p < .001). Finally, environmental conditions (e.g. ambient temperature: sr2 = .53, p < .001) were more reliable predictors of piloerection than participants' subjective reports (e.g. self-reported coldness: sr2 = .02, p = .107) , challenging its treatment as a purely affective response in humans.

Conclusion: This research fundamentally challenges the prevailing understanding of piloerection in humans, presenting it not as an emotional artifact but as a nuanced physiological response to a variety of environmental stimuli. By demonstrating that human piloerection mirrors its function in other species, this study highlights the evolutionary continuity of physiological responses across species. The implications of these findings suggest a need to reconsider the role of piloerection in human physiology and psychology, from a marker of emotional states3 to a broader indicator of sensory and environmental engagement.


Diverse stimuli induce piloerection and yield varied autonomic responses in humans

Since the introduction of global shipping lanes, the European green crab (Carcinus maenas) has become a highly successful invasive species, colonizing every continent except for Antarctica. First sighted in San Francisco Bay, CA in 1989, the invasive green crab population quickly spread to Vancouver Island, BC in less than 10 years. Upon introduction, a comparatively high tolerance to fluctuations in temperature and salinity allows C. maenas to outcompete native crustacean species for habitats and resources. Given that nearly 30% of the Canadian Pacific Coastline is considered marine protected area, harbouring critical native species and habitats, understating the factors influencing the survival and spread of C. maenas may be vital in mitigating their harm. Additionally, the estuarine coastline of Vancouver Island offers a highly variable environment, with salinity ranging anywhere from full strength sea water, to dilute freshwater inputs. Here, using a multi-stressor approach, we evaluated the upper thermal tolerance of the green crab in combination with variable salinity. In particular, we investigated how changes in environmental salinity influenced the critical thermal maximum (CTmax) of the green crab. First, six male crabs were assigned to each of the following treatment groups, 100% salinity, 50% salinity, 20% salinity, and acute 0% salinity, then CTmax was assessed. Interestingly, no significant differences in CTmax were found in response to changes in environmental salinity, exhibiting a CTmax of approximately 37.6 ± 0.3 °C. In response to changes in salinity, heart rate, temperature induced maximum metabolic rate, resting metabolic, and freshwater LT50 are also evaluated at various temperatures. This research offers valuable information regarding C. maenas’ tolerance to environmental stress related to variable estuarine environments, which may play a vital role in predicting and thus mitigating their invasive success on the Canadian Pacific Coastline.

The influence of variable salinity on invasive green crab (C. maenas) survival in Canadian Pacific estuaries.

Experimental variation is a multi-faceted phenomenon leading to both intra-experimental and inter-experimental incongruencies. Such variation often manifests in nonreproducibility of experiments which is rightfully regarded as an issue in experimental sciences. Nonreproducibility has been attributed to inadequate reporting of methods, sloppiness/honest error, and even misconduct. We hypothesized that, within the field of animal physiology, the most parsimonious explanation for nonreproducibility is inadequate reporting of key methodological details. We analyzed 84 research articles published in five primarily organismal animal physiology journals and assessed compliance for 34 reporting variables referring to biology, experimentation, and data collection/analysis. Our study shows that about one third of necessary information on the methodology is missing. We thus assume that at least within the life sciences, underreporting of key variables can lead to a lack of reproducibility that is independent of the rigor of the study, but rather reflects the lack of rigor of the journal article preparation as well as peer review and publishing.

Addressing Nonreproducibility: Examining Methodological Reporting in Animal Physiology Studies

Plants are sessile organisms adapting constantly to environmental fluctuations through spatial and temporal transcriptional responses. We used the latest generation of MS2 RNA labelling system combined with microfluidics to monitor impact of modification of phosphate supply by live transcription imaging. MS2/MCT system is based on a fusion between GFP and the coat protein of bacteriophage MS2 (MCP-GFP), which recognizes a specific RNA stem-loop inserted in multiple copies into a reporter RNA. This enabled quantitative measurements of the transcriptional activity of single loci in living Arabidopsis plants, providing direct visualization of transcriptional regulation within entire organs. Using phosphate responsive genes as model, we found that active genes displayed high transcription initiation rates and frequently clustered together in endo-replicated cells. We also observed large differences between alleles of single cells and in agreement, intrinsic noise was larger than extrinsic variations. Moreover, we established that the transcriptional repression triggered in roots by phosphate, a crucial macronutrient limiting plant development, occurred with unexpected fast kinetics in the range of minutes, and with striking heterogeneity between neighboring cells. Access to single cells RNA polymerase II dynamics within live plants will benefit the study of numerous signaling processes.

RNA live imaging: interest for plant biology

Temperature is a key determinant of plant distribution and phenology. Warmer temperatures due to climate change have already altered the flowering times of wild plants, and crop yields decline significantly with additional temperature stress. Despite the importance of temperature on plant growth and development, little is understood of the mechanisms of temperature sensing in plants. We have identified thermosensory nodes that can account for key warm temperature responses for both stress and developmental pathways. We have found that protein phase change appears to play a role in several temperature response pathways, and I will describe some of these in Arabidopsis thaliana.

Temperature sensing in plants

Plants experience heat stress (HS) at temperatures where growth and development are negatively affected. Survival from HS is dependent on the upregulation of hundreds of genes with protective functions for protein and cellular homeostasis such as heat shock proteins (HSPs). The majority of these genes are regulated by the family of HS transcription factors (HSF). In tomato, HsfA1a is the master regulator of HS response. Additional HSFs, such as HsfA2 and HsfA7 are important for HS acclimation and memory, the ability of a plant to store the information of a past HS incident and optimize the response in case of a new one. Class B HSFs act as co-activators and co-repressors and regulate the intensity and the timely attenuation of the stress response to optimize recovery. In addition to transcription, RNA splicing is another important mechanism for regulation of gene expression under HS conditions. Our results suggest that thermotolerance requires the coordinated but also independent activity of transcription factors and splicing regulators to optimize the cellular reprogramming required for survival under high temperatures.

Heat stress transcription factors and splicing regulators: brothers in arms to survive heat

Genome specific association study (GSAS) for exploration of intravarietal variability in hemp (Cannabis sativa)

Trubanová Nina (1); Isobe Sachiko (2); Shirasawa, Kenta (2); Watanabe, Akiko (2); Melzer, Rainer (1, 3), Schilling, Susanne (1, 3)

1 School of Biology and Environmental Science, University College Dublin, Science Centre West, Belfield, Dublin 4, Republic of Ireland; 2 Laboratory of Plant Genetics and Genomics, Department of Frontier Research and Development, Kazusa DNA Research Institute; 3 UCD Earth Institute, University College Dublin

Hemp (Cannabis sativa L.) stands out as a versatile crop with substantial economic potential. However, its intravarietal phenotypic and genetic variability remain inadequately elucidated. In the context of advancing crop improvement efforts, our research addresses this gap by employing an innovative genome-specific association study (GSAS) framework.
The GSAS methodology involves the streamlined generation of a single phenotyped population, the selection of alleles heterozygous in the parent plant, and the application of a model conducive to the polygenic association of studied traits. Through extensive exploration of plant growth, development, and reproductive patterns, along with genetic variability analysis of a population derived from a single plant, we identified statistically significant single nucleotide variants and haplotypes associated with studied traits.
Here presented study highlights the potential of the GSAS approach for utilising genomics and phenomics to significantly advance our understanding of the genetic determination of intravarietal phenotypic variability in hemp and other highly heterozygous crops. The findings from prospective GSAS studies hold promise for marker-assisted breeding, enabling the development of new cultivars with enhanced uniformity and improved performance in traits relevant to various applications, ranging from pharmaceuticals to the manufacturing of materials with superb properties, adaptable to various climates.

Genome specific association study (GSAS) for exploration of intravarietal variability in hemp (Cannabis sativa)

This talk is split into two parts. I will first examine whether there is sufficient evidence for male ejaculate senescence across the animal kingdom. I will present data from a meta-analysis we conducted on 379 studies, to quantify the effects of advancing male age on ejaculate traits across 157 species of non-human animals. This work shows that there is high heterogeneity in the available data, hence I will try to tease apart the factors that might explain this variation. In the second part of the talk, I will focus on ejaculate and reproductive senescence in the model organism Drosophila melanogaster and try to identify the molecular drivers, contributing factors and fitness consequences of advancing male age for the male, its female mate and for its offspring.

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The cGMP/PKG pathway, but not the cAMP/PKA pathway promotes branchial ammonia excretion in the green shore crab

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