Czechia

Improving crop intrinsic water use efficiency (iWUE) usually comes at the expense of carbon assimilation. Sorghum is a key crop in many vulnerable agricultural systems with higher tolerance to water stress (WS) than other crops. To investigate physiological controls on iWUE and its inheritance in sorghum we screened 90 genotypes selected based on inherited haplotypes from an elite or five exotics lines, which included different aquaporin (AQP) alleles. We found significant variation among key highly heritable gas exchange and hydraulic traits. Plants with a higher proportion of the non-stomatal component of iWUE still maintained iWUE under WS by maintaining photosynthetic capacity, independently of reduction in leaf hydraulic conductance. Haplotypes associated with two AQPs (SbPIP1.1 and SbTIP3.2) influenced iWUE and related traits. These findings expand the range of traits that bridge the trade-off between iWUE and productivity in C4 crops, and provide possible genetic regions that can be targeted for breeding.

SEB Conference Prague 2024

Hydraulic and stomatal controls on water use efficiency in a sorghum sub-population with varying aquaporin alleles

stomatal conductance

aquaporins

water use efficiency

sorghum

photosynthesis

water stress

technical paper

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Teleosts maintain body fluid ionic and acid-base homeostasis through energy-consuming ion transport mechanisms in the gills and other organs. Our serial studies identified a new gill cell type (GR cells) in zebrafish and tilapia, which are rich in glycogen and provide glucose or lactate/pyruvate to neighboring ionocytes. Different types of glucose and monocarboxylate transporters were found to facilitate energy deposition and supply between ionocytes and GR cells. On the other hand, ammonotelic fishes are suggested to rely on ammonia excretion to enhance net acid secretion because ammoniogenesis produces HCO3- to facilitate body fluid acid-base homeostasis. We recently extended our study to understand how ammoniagenesis occurs and is coordinated with ammonia excretion in fish gills. In medaka and other species, we have discovered an undiscovered ammonia-producing cell type that is rich in glutaminase (GLS cells) and located adjacent to the ammonia-excreting ionocytes (NHE cells) in the gills. The unique division of labor between GLS and NHE cells in the gills allows medaka to simultaneously upregulate GLS activity and ammonia excretion shortly after exposure to acidic environments. These findings provide fundamental information to enhance our mechanistic understanding of the energy metabolism underpinning gill ion transport functions and the related physiological adaptations of vertebrates during evolution.



Ion regulation and related energy metabolism in fish gills

The Giant Grouper (Epinephelus lanceolatus) is an important species in aquaculture industry of Taiwan. However, during the fry stage, susceptibility to nerve necrosis virus (NNV) poses a considerable challenge, impacting the industry substantially. Furthermore, as a species inhabiting tropical and subtropical regions, environmental temperature serves as a critical factor influencing grouper physiology, potentially modulating the expression of disease resistance genes. Previous research highlights the importance of interferon in the antiviral pathway, with protein kinase R downstream playing a crucial role in disease and stress resistance. This study aims to investigate the effects of hypothermal stress and NNV on giant grouper through PKR gene expression analysis. The results indicate that low temperatures elevate PKR expression in giant grouper larvae, consequently inhibiting NNV replication. Therefore, low temperatures may assist giant grouper larvae in avoiding NNV infection. This study further explored the effects of hypothermal stress and NNV on grouper protein kinase R expression, offering insights into disease resilience mechanisms.

Effects of Hypothermic Stress on Giant Grouper (Epinephelus lanceolatus) PKR Gene Expression and Antiviral Response Against NNV

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.

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

Embryonic Gulf killifish (Fundulus grandis) exhibit precocial parasympathetic-mediated cardiac control, yet little there is little research concerning their unusually early vagal tone. These embryos feature traits uniquely suited for studying early ANS development as 1) they require no anesthesia, thereby eliminating collateral interference that anesthetics have on the ANS or cardiovascular system, 2) feature a semi-transparent chorion, enabling direct observation of the heart, and 3) possess a fully sequenced and annotated genome conducive to understanding genotype-phenotype relationships. Parasympathetic inhibition of the heart created by a ‘startle’ response is evident as a transient cardiac arrest and can be performed by applying gentle mechanical pressure to the embryos under a glass microscope slip, followed by atropine administration upon positive observation of vagal tone. Habituation assays were performed to determine whether an attenuated vagal response to repeated startle stimuli emerged over time, a further expression of early cardiac control. This included obtaining trace data of cardiac activity using a high-throughput heart monitor system for fish embryos. At 80% to hatch a startle stimulus induces transient bradycardia for ~30-40sec. This parasympathetic response was blocked by 1 mmol atropine. Cardiac activity observed during habituation assays showed a non-diminished susceptibility to induced bradycardia. Embryos as young as 60-70% to hatch (~9 days post-fertilization) exhibit vagal tone through parasympathetic stimulation, signifying the initial vagal innervation of the heart. Exploiting this precocial onset of parasympathetic innervation in Gulf killifish embryos can serve as an interface linking established genotypes to relevant physiological phenotypes.

Onset of Cardiovascular Regulation by Vagal Innervation of the Heart in Embryonic Gulf Killifish Embryos (Fundulus grandis)

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

Protein-protein interaction (PPI) network topology determines properties of genes, such as expression levels, or levels of evolutionary constraint. When genes are central to a network they are more likely to be conserved and highly expressed, whereas genes that are able to change in response to evolutionary pressures but expressed at lower levels are located on the periphery of the network. We used transcriptomic data of zebrafish (Danio rerio) embryos to compare the PPI properties of the response to two environmental stressors (heat, UVR and combination). We show that genes with stress response Gene Ontology are situated centrally to the PPI network. The transcriptomic response to heat occupied central and peripheral positions within the reference network, whereas UV response occupied central and intermediate positions. Prefacing UVR with heat led to a downshift of DEGs, which could explain the hormetic effect of heat stress. In addition, when only considering genes specific to each stressor, heat responsive DEGs were located more peripherally, and uniquely UV responsive DEGs were located intermedially in the PPI. Overall, these results support the idea that the stress response must have both conserved and derived aspects, in order to respond to stress generally but to also allow for specialisation, which we show to be reflected in the PPI network architecture. These properties can aid in better understanding the organismal response to diverse and co-occurring environmental stressors.

The protein-protein interaction network architecture of the environmental stress response in zebrafish embryos

Wildfire prevalence has increased drastically around the world, exacerbated by climate change, resulting in devastation to ecosystems and the organisms therewithin. Australian bushfires are of particular concern given Australia’s extensive biodiversity and numerous endemic species. While terrestrial impacts are often the primary concern for fires, the aquatic environment is also at risk. Ash from fires can directly descend into aquatic environments or be introduced as runoff, and which can release heavy metals and contaminants such as polyaromatic hydrocarbons. The physiological effects of bushfire ash on aquatic animals are not well understood, nor is their subsequent coping and recovery ability. Two native Australian freshwater species, the long-armed shrimp (Macrobrachium australiense) and the blue yabby (Cherax destructor), were selected to examine their physiological responses following exposure to Australian bushfire ash. We found that the shrimp were significantly more sensitive to ash than the crayfish. Metabolic oxygen consumption was measured, and the enzymatic activity of cytochrome c oxidase and lactate dehydrogenase were assessed in three tissue types (gills, hepatopancreas and muscle). Thus, insight is gained into the species method of cellular respiration. The sensitivity and effects of ash exposure are important to adequately evaluate the effects of bushfires. The ability for animals to contend with ash exposure will allow for identification of critical areas where monitoring and conservation efforts should be made following bushfires.

Swimming in ash: Comparing physiological responses of two freshwater crustaceans to Australian bushfire ash

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.

Rice is one of the major global food crops. Although the overall yield of rice has been increasing, the growing population and adverse climatic changes pose huge challenges for their sustained production in the future. Therefore, systematic approaches are highly required to explore their effects on cereal crops’ phenotypic and cellular responses. It could be achieved by combining the available multiple high throughput data such as genomics, metabolomics, proteomics and transcriptomics, thereby analyzing the possible biochemical adaptations to several abiotic and biotic stresses, and subsequently improving the crop yield. Concurrently, the advent of constraint-based metabolic reconstruction and analysis paves way to characterize cellular physiology under various stresses via the mathematical network models. We have employed similar systems biology approach, and initially developed a core mathematical model of rice to characterize cellular behaviour and metabolic states under various abiotic stress conditions. The core model was then further expanded to reconstruct a fully compartmentalized genome scale metabolic model. Subsequently, transcriptomics and metabolomics data were systematically integrated with the model to identify the potential candidate regulatory genes as new breeding targets for improving rice production. In addition, we have also reconstructed a genome-scale metabolic model of Xanthomonas oryzae pathovar oryzae (Xoo) that causes leaf blight in rice leading to severe yield losses. In future, in silico model-guided framework can be further extended by including comprehensive genome-scale model of rice and its leaf microbiome for characterizing their interactions. This may allow us to systematically devise new strategies to control leaf blight in rice.

Plant systems biology: application to rice for understanding cellular phenotype to guiding crop improvement under abiotic and biotic stress conditions

Quantifying trade-offs between life history traits is complex. In particular, the extent of trade-offs between reproduction and somatic maintenance remains difficult to quantify in wild animals. Using the dynamic nature of telomeres may help to elucidate this process. Telomere length (TL) is generally associated with longevity, as it tends to shorten with age, and can thus serve as a biomarker associated with future survival. However, TL varies widely among individuals within a population, as it can be influenced by individual and environmental factors. An increased reproductive effort appears to accelerate telomere erosion, making TL a potential biomarker to describe the trade-off between reproduction and future survival. On the other hand, TL partially explains individual performance, with longer telomeres being associated with higher reproductive success.
This study investigates the factors contributing to TL variation among female Tree swallows (Tachycineta bicolor) from a wild population in southern Québec, Canada. Specifically, it assesses the effects of individual (ex. age, reproductive traits) and environmental (ex. habitat quality, density) factors on TL variation within and between females over the course of a breeding season in this species. Our results improve our understanding of telomere dynamics in wildlife populations and their potential use as biomarkers of reproductive performance.

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Ion regulation and related energy metabolism in fish gills

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