Czechia

The interaction of widespread stressors such as nitrate pollution and increasing temperatures associated with climate change are likely to affect aquatic ectotherms such as amphibians. The metamorphic and physiological traits of amphibian larvae during the critical onset of metamorphosis are particularly susceptible to these stressors. We conducted a common-garden experiment using Rana temporaria larvae subjected to four constant acclimation temperatures (18, 22, 26, 28 °C) crossed with three environmentally relevant nitrate concentrations (0, 50, 100 mg × L-1) to investigate the interactive and individual effects of these stressors on metamorphic (i.e., growth and development) and physiological traits (i.e., metabolism and heat tolerance) at the onset of metamorphosis. Larvae exposed to elevated nitrate concentrations and thermal stress displayed increased metabolic rates but decreased developmental rate, highlighting interactive effects of these stressors. However, nitrate pollution alone had no effect on either metamorphic or physiological traits, suggesting that detoxification processes were sufficient to maintain homeostasis but not in combination with increased acclimation temperatures. Furthermore, larvae exposed to nitrate displayed diminished abilities to exhibit temperature-induced plasticity in metamorphosis timing and heat tolerance, as well as reduced acclimation capacity in metabolic rate and heat tolerance to higher temperatures. These results highlight the importance of considering the exposure to multiple stressors when investigating how natural populations respond to global change.

SEB Conference 2024

Navigating ontogenetic pathways: amphibian developmental plasticity in a changing world

acclimation capacity

global warming and envrionmental pollution

developmental plasticity

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technical paper

Maintaining pH homeostasis is not only require for the biomineralization process of marine calcifiers but also essential to their adaptation streitige against the environmental challenge such as ocean acidification. The calcareous endoskeleton of sea urchin larva, which benefits from years development of gene regulatory networks, ex vivo tissue engineering technique and in vivo gene manipulation approaches, becomes a powerful model for biomineralization research. Based on the model organism Strongylocentrotus purpuratus, our research group discovered a serial transporters and enzymes that are critical to cytosolic pH (pHi) regulation in skeletogenic cells. The cytosolic bicarbonate sensor soluble adenylyl cyclase (sAC) is one of these factors which might play the central role regulating intracellular pH homeostasis. The cAMP signaling triggered by activated sAC may further stimulates the channel activity and gene expression of pH effectors in skeletogenic cell. In order to investigate the interaction between cAMP signaling and pH-regulating transporters, we developed skeletogenic cell-specific gene expression approaches. According to our preliminary results, the activity of sAC is possibly regulated through its alternative splicing, and the splicing event is stimulated by skeleton regeneration. Further evidences are required to clarify the regulation of sAC splicing event and cytosolic pH homeostasis that initiated by cAMP signaling. The present study demonstrates a canonical cellular stress response that a sensory factor reacts to environmental stimulation through post-transcriptional modification.

Soluble adenylyl cyclase regulates intracellular pH homeostasis of calcifying cells in the sea urchin larva.

A marine biogeographic and phylogeographic break around 30°S along the shores of the southeastern Pacific coincides with a mesoscale change in coastal upwelling regime. Prior ecological and genetic evidence indicated that dispersal limitation was the leading mechanism maintaining the break. Recent evidence of large environmental heterogeneity between sites along the transitional zone provides support for a niche-based mechanism as the underlying driver. To test this hypothesis, we examined patterns of phenotypic plasticity under contrasting thermal conditions for species belonging to several taxa and multiple trophic levels, which were sourced from local populations spanning the biogeographic break. We pooled plasticity patterns with data from similar studies over multiple sites spanning the break and examined their joint spatial structure and its relationship with environmental heterogeneity. We observed that regardless of taxa and trophic level, individuals from populations within the biogeographic break showed higher phenotypic plasticity. Similarly, the spatial structure in neutral genetic markers for this diverse set of benthic species, which either spanned the transition zone or found the edge of their geographic ranges around it, hints at the presence of local adaptation. Our results suggest that evolutionary novel ecological interactions are taking place under environmental conditions that challenge species’ physiological limits. The species that span the transition zone are able to persist locally likely through a net influx of propagules; the strong selective pressure highlighted by plasticity patterns, together with our tentative evidence for local adaptation, suggests that the region may represent an area of special interest for future conservation efforts

Spatial patterns in phenotypic plasticity across a marine biogeographic transition zone: an eco-evolutionary driver?

Dissolved oxygen is a key environmental parameter for aquatic life. In two sets of experiments we evaluated the effect of long-term changes in the dissolved oxygen environment on the morpho-physiology and behaviour of the weakly electric fish Petrocephalus degeni. First, we captured fish from a severely hypoxic habitat in Uganda and acclimated them to normoxic conditions for up to 73 days while measuring respirometric and morpho-physiological traits in the field. In the second experiment, we used fish that had been kept under normoxic conditions for over two years in the laboratory. We assessed their hypoxia avoidance behaviour as well as physiological traits before and after 56 days of exposure to hypoxic conditions (15% air saturation). We found that gill size changed significantly in both experiments. Blood haemoglobin concentration was only affected during normoxia acclimation. Other traits, such as critical oxygen tension and hypoxia avoidance behaviour, were unaffected by the acclimation treatment. Our results suggest that P. degeni remain remarkably hypoxia tolerant throughout acclimation to different oxygen environments. Plasticity in respiratory traits that are directly associated with oxygen extraction and carrying capacity likely facilitates the homeostasis of higher-level traits linked to hypoxia tolerance, such as critical oxygen tension and hypoxia avoidance, by optimizing energetic trade-offs in different dissolved oxygen environments.

Plasticity in respiratory traits and stable hypoxia tolerance in a weakly electric fish exposed to long-term changes in dissolved oxygen environment

Healthy microbiota is very important for its host although defining it can be challenging because the composition of the microbiota is very diverse and highly variable depending on, for example, environment, genetics, and host health status. Drastic changes in environment or lifestyle can lead to the imbalance of microbiota. This can be problematic as healthy microbiota have myriad positive functions, including protection of a host from invasion of pathogenic bacteria and modulation of the immune system. We studied the effects of environmental conditions (water temperature and oxygen concentration) on zebrafish skin microbiota. We found that genotype did not have an effect on skin microbiota composition and extreme changes in water temperature only had a relatively minor effect. We further demonstrated that zebrafish skin microbiota composition changed when water temperature and oxygen concentration were altered but these perturbations did not permanently shift skin microbiota composition. Finally, we compared gut microbiota composition of healthy horses and horses suffering from inflammatory bowel disease (IBD). We show that IBD did not cause a dysbiosis in the entire gut microbiota but only approximately 200 OTUs (less than 1% of all analyzed OTUs) showed a significant increase or decrease in response to IBD. However, a metabolomic analysis revealed that the functioning of microbiota differed between healthy and IBD-horses. Overall, our results show that while zebrafish skin and horse gut microbiota appear robust and resilient to perturbations. However, a closer look revealed that the abundance of certain pathogenic bacteria was increased and microbiota metabolic were functions altered.

The robustness and resilience of skin and gut microbiota

Inter-individual variability is the range of phenotypes produced between conspecifics within a population, and such variability is ubiquitously observed among animals. Investigating inter-individual variability can help develop a more comprehensive understanding of how phenotypes respond to environmental change. The Baja California chorus frog (Pseudacris hypochondriaca) is a thermally robust species found in a variety of ecosystems that differ in temperature and elevation throughout its latitudinal range (∼1400 km) from Santa Barbara County, California to Baja California, Mexico. We aimed to investigate how inter-individual variability in developmental traits changes within and between temperatures. Chorus frog eggs were incubated as eggs and tadpoles at 15°C or 22°C. Once tadpoles reached Gosner Stage 33 (hind limb toe differentiation), oxygen consumption rate (V̇O2), swimming speed, and morphology were measured. Average time to stage, wet mass, dry gut-free mass and body length all decreased at 22°C, while mass-specific V̇O2 and swimming speed increased. We observed decreased variability at 22°C compared to 15°C in time to reach stage, wet mass, dry gut-free mass and body length. In contrast, variability in mass-specific V̇O2 increased at 22°C and variability in swimming speed was unchanged between temperatures. Overall, the effect of temperature on inter-individual variability is trait-specific and should be explored further to understand the implications of temperature-induced plasticity.

Inter-individual variability in developmental traits in tadpoles of the Baja California chorus frog (Pseudacris hypochondriaca) in response to temperature

Cell division plane (CDP) orientation and cell growth directionality, determine tissue patterning and organ formation. A core component of CDP orientation is the preprophase microtubule band (PPB). It is known that PPB is physically associated with the plasma membrane (PM) requiring recruitment of scaffold proteins with affinity towards specific PM lipids and for proteins associated with microtubules. The mechanisms underlying the determination of CDP orientation are being vigorously studied. Yet, the specific identity and the role of PM lipids in the recruitment of scaffold proteins remain elusive. Sterols, a major lipid group forming nanodomains at the PM, play vital roles in cellular processes such as endocytosis, cell polarity and, cell expansion. Moreover, early studies on Arabidopsis sterol biosynthesis mutants have described severe developmental defects. However, no mechanism of implication of sterol biosynthesis deficiency in the determination of cell division has yet been proposed. Here, we have revisited the role of structural sterol biosynthesis on Arabidopsis vegetative growth and tissue patterning, as contrasted defects arising from compromised production of brassinosteroids, focusing on how CDP specific microtubule arrays are formed. Sterol biosynthesis mutants cpi1-1 and smt2smt3 showed defective vegetative phenotypes and disrupted histological pattern, as exemplified in the root. Aberrant mitosis with ectopic cell divisions. The smt2smt3 showed more severe phenotype than cpi1-1 indicating a possible role of structural phytosterols in the determination of CDP. Pharmacological treatments with sterol biosynthesis inhibitors phenocopied the sterol biosynthesis mutants. To conclude, cell division abnormalities are due to sterol biosynthesis pathway rather than brassinosteroids biosynthesis.

Impairment of sterol biosynthesis affects cell division and cell division plane orientation

Nitrogen is one of the most limiting nutrients for plant growth and is required in large amounts due to its role as a building block for essential molecules such as nucleic acids, chlorophyll, and proteins. As such, nitrogen application in the form of synthetic fertilizers is required to significantly increase crop yield and sustain a growing world population. We recently described the buzz root hairless mutant in Brachypodium distachyon. RNAseq analysis found an upregulation of nitrate transporters, NRT1.1A, NRT1.1B, and CIPK23 in the buzz mutant. In addition, RNAscope revealed partial colocalization of BUZZ mRNA and NRT1.1A in root hair tips. BUZZ also appears to mediate both primary and lateral root growth in a nitrate-dependent manner. Since evidence showing a direct link between root hairs and nitrogen acquisition is lacking in grasses, identifying additional components involved in nitrate acquisition as well as root hair growth can assist in efforts to improve NUE in cereal crops. We evaluated primary nitrate-responsive genes in the buzz mutant and found upregulation of NRT1.1, NRT2.1, TGA4, and NR1 in low nitrate conditions. We further determined nitrate uptake and nitrate use efficiency in buzz versus wild-type plants with normal root hairs. We also report the identification of five proteins that interact with BUZZ and functionally characterize them. Taken together, these data provide the foundational evidence of a heretofore unidentified genetic network that underlies nitrate responses in grasses and that also challenges the importance of root hairs in the uptake of this essential nutrient.

BUZZed on Nitrate: The effect of a root hairless mutant on nitrate acquisition in the model grass Brachypodium distachyon

Phenotypic plasticity, both within and between generations, allows organisms to respond to a changing world. Here, we aim to investigate how paternal phenotypes interact to shape offspring life-histories, focussing on two ubiquitous animal experiences: ageing and feeding. We present preliminary results from an ongoing experiment using Drosophila melanogaster: a full-factorial design, where fathers were fed one of two diets (control and higher-sucrose) and male and female offspring collected when fathers were young (one week) and old (five weeks). These offspring were then assigned to diets either matching or mismatching those of their fathers, and their survival and weekly reproductive output measured. We find complex interactions between paternal age, paternal diet, and offspring diet shape different aspects of offspring life-history, in a sex-specific manner. This investigation illuminates how organisms cope with environmental variation over their own lifespans and between generations, exploring the myriad forms of information parents transfer to their offspring, and the conditions under which this occurs.

Paternal age and environment effects on offspring life-history traits and fitness in Drosophila melanogaster

Parental age effects occur when offspring of older parents are of lower quality than offspring of younger parents. I will (1) present my research group’s evidence for parental age effects on offspring lifespan, reproduction, and fitness in aquatic plants in the genus Lemna (duckweeds); and (2) discuss the theoretical consequences for these effects on the evolution of senescence.

Parental age effects and offspring fitness in a clonally reproducing aquatic plant

Telomere length in early life is predictive of longevity in many species and reduced early life telomere length in offspring of older mothers has been linked to the reduced longevity frequently found in offspring of older breeders (the Lansing Effect). It is currently unknown whether such telomere reduction may persist beyond a single generation, as would be the case if germline transmission is involved. To test this, we performed a within-grandmother, multi-generational study using zebra finches. Our results indicate that shorter telomeres persist in offspring whose grandmothers were old at the time of their mother´s birth, despite their mother having been a young breeder. Our data highlight the need to look beyond a single generation to explain the causes of inter-individual variation in ageing rates and optimal reproductive schedules.

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Soluble adenylyl cyclase regulates intracellular pH homeostasis of calcifying cells in the sea urchin larva.

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Capacity for rapid thermal acclimation differs between life stage and species in fish

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Next from SEB Conference 2024

Soluble adenylyl cyclase regulates intracellular pH homeostasis of calcifying cells in the sea urchin larva.

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Capacity for rapid thermal acclimation differs between life stage and species in fish

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PRESENTATIONS

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