scholarly journals The functional response of the Antarctic bivalve Laternula elliptica to ocean warming and acidification

2021 ◽  
Author(s):  
◽  
Sonja Hempel
Keyword(s):  
Gene Expression ◽  
Elevated Temperature ◽  
Heat Shock ◽  
Physiological Condition ◽  
Ocean Warming ◽  
Hsp70 Gene ◽  
Time Points ◽  
Laternula Elliptica ◽  
Shock Response ◽  
The Antarctic

<p>Marine life is currently under threat from large-scale, long-term changes to the marine environment. Anthropogenic emissions of greenhouse gases, particularly carbon dioxide (CO₂), are causing ongoing change to global marine systems, particularly through ocean warming and acidification. Greenhouse gases in the atmosphere are trapping radiation and heating the entire Earth surface, including the ocean. At the same time, oceanic uptake of CO₂ through absorption by surface waters is altering ocean chemistry, increasing acidity, reducing availability of carbonate ions (CO₃²⁻), and causing increasing dissolution of calcium carbonate (CaCO₃) structures.  Because atmospheric CO₂ diffuses more readily into cold water, the Southern Ocean (SO) will experience ocean acidification in a matter of decades. Warming in the SO is also occurring rapidly and represents a comparatively greater increase in temperature than elsewhere. SO marine fauna have evolved in constant, stable, cold conditions, and as a result are stenothermal and particularly at risk from ocean warming and acidification. The large infaunal bivalve Laternula elliptica is a prevalent keystone species found throughout the Antarctic benthos in high numbers, and contributes significantly to biodeposition and bentho-pelagic coupling.  This thesis examines how L. elliptica adults are affected over medium-term (5-mo) timescales by SO warming and acidification. Adult L. elliptica collected from Cape Evans in McMurdo Sound, Antarctica, were subjected to combinations of temperatures and pHs predicted for the SO by 2050 and 2100 (Temperatures: -1.4°C (control); -0.5°C; +0.5°C. pHs: pH 8.00 (control); pH 7.85; pH 7.65). L. elliptica were assessed at 5 wk and 5 mo to determine their cellular, metabolic, and whole-organism responses to temperature increase and/or pH decrease. Survival parameters such as final survival percentage, survival curves, and time to 50% survival (LD₅₀) were compared among treatments. L. elliptica survival was severely reduced by warming of only 1-2°C above summer ambient temperatures. Physical and physiological condition indices were calculated to assess health, and show changes in shell and body tissue mass. Physical condition stayed similar amongst all treatments at both time points, while physiological condition decreased significantly at 5 mo with elevated temperature. Oxygen (O₂) consumption was measured as a proxy for standard metabolic rate to show whether animals had acclimatised to conditions. O₂ consumption was significantly negatively correlated with physiological condition, and increased, becoming more variable, with both elevated temperature and lowered pH. This indicated that L. elliptica experienced increased metabolic demand in response to these conditions, and there was a general lack of acclimation to these conditions over time. Overall, pH had no significant effect on survival, metabolic rate, or condition. Heat shock protein 70 (HSP70) gene expression levels were measured to provide a preliminary indication of how the heat shock response of L. elliptica responds to both elevated temperature and reduced pH. Lowered pH appeared to stimulate an up-regulation of HSP70 gene expression at both time points, although this was smaller at 5 mo. L. elliptica did not seem to display a heat shock response at environmentally realistic levels of warming.  Overall, warming resulted in lowered survival and condition loss with no sign of acclimation after 5 mo. These responses occurred at smaller degrees of warming than are typically considered lethal for L. elliptica, indicating that successful longer-term maintenance is more thermally limited than short-term survival in this species. While physical (shell) condition was maintained in undersaturated conditions under both elevated temperature and reduced pH, this maintenance occurred alongside increased O₂ demand. Maintaining the aragonitic shell in combination with increased metabolic activity may have contributed to the decline in physiological (body mass) condition observed in L. elliptica. In combination, the results of this experiment indicate that warming of the SO may be more important than ocean acidification to the survival and functioning of adult L. elliptica.</p>

scholarly journals The functional response of the Antarctic bivalve Laternula elliptica to ocean warming and acidification

2021 ◽  
Author(s):  
◽  
Sonja Hempel
Keyword(s):  
Gene Expression ◽  
Elevated Temperature ◽  
Heat Shock ◽  
Physiological Condition ◽  
Ocean Warming ◽  
Hsp70 Gene ◽  
Time Points ◽  
Laternula Elliptica ◽  
Shock Response ◽  
The Antarctic

<p>Marine life is currently under threat from large-scale, long-term changes to the marine environment. Anthropogenic emissions of greenhouse gases, particularly carbon dioxide (CO₂), are causing ongoing change to global marine systems, particularly through ocean warming and acidification. Greenhouse gases in the atmosphere are trapping radiation and heating the entire Earth surface, including the ocean. At the same time, oceanic uptake of CO₂ through absorption by surface waters is altering ocean chemistry, increasing acidity, reducing availability of carbonate ions (CO₃²⁻), and causing increasing dissolution of calcium carbonate (CaCO₃) structures.  Because atmospheric CO₂ diffuses more readily into cold water, the Southern Ocean (SO) will experience ocean acidification in a matter of decades. Warming in the SO is also occurring rapidly and represents a comparatively greater increase in temperature than elsewhere. SO marine fauna have evolved in constant, stable, cold conditions, and as a result are stenothermal and particularly at risk from ocean warming and acidification. The large infaunal bivalve Laternula elliptica is a prevalent keystone species found throughout the Antarctic benthos in high numbers, and contributes significantly to biodeposition and bentho-pelagic coupling.  This thesis examines how L. elliptica adults are affected over medium-term (5-mo) timescales by SO warming and acidification. Adult L. elliptica collected from Cape Evans in McMurdo Sound, Antarctica, were subjected to combinations of temperatures and pHs predicted for the SO by 2050 and 2100 (Temperatures: -1.4°C (control); -0.5°C; +0.5°C. pHs: pH 8.00 (control); pH 7.85; pH 7.65). L. elliptica were assessed at 5 wk and 5 mo to determine their cellular, metabolic, and whole-organism responses to temperature increase and/or pH decrease. Survival parameters such as final survival percentage, survival curves, and time to 50% survival (LD₅₀) were compared among treatments. L. elliptica survival was severely reduced by warming of only 1-2°C above summer ambient temperatures. Physical and physiological condition indices were calculated to assess health, and show changes in shell and body tissue mass. Physical condition stayed similar amongst all treatments at both time points, while physiological condition decreased significantly at 5 mo with elevated temperature. Oxygen (O₂) consumption was measured as a proxy for standard metabolic rate to show whether animals had acclimatised to conditions. O₂ consumption was significantly negatively correlated with physiological condition, and increased, becoming more variable, with both elevated temperature and lowered pH. This indicated that L. elliptica experienced increased metabolic demand in response to these conditions, and there was a general lack of acclimation to these conditions over time. Overall, pH had no significant effect on survival, metabolic rate, or condition. Heat shock protein 70 (HSP70) gene expression levels were measured to provide a preliminary indication of how the heat shock response of L. elliptica responds to both elevated temperature and reduced pH. Lowered pH appeared to stimulate an up-regulation of HSP70 gene expression at both time points, although this was smaller at 5 mo. L. elliptica did not seem to display a heat shock response at environmentally realistic levels of warming.  Overall, warming resulted in lowered survival and condition loss with no sign of acclimation after 5 mo. These responses occurred at smaller degrees of warming than are typically considered lethal for L. elliptica, indicating that successful longer-term maintenance is more thermally limited than short-term survival in this species. While physical (shell) condition was maintained in undersaturated conditions under both elevated temperature and reduced pH, this maintenance occurred alongside increased O₂ demand. Maintaining the aragonitic shell in combination with increased metabolic activity may have contributed to the decline in physiological (body mass) condition observed in L. elliptica. In combination, the results of this experiment indicate that warming of the SO may be more important than ocean acidification to the survival and functioning of adult L. elliptica.</p>

scholarly journals tRNA thiolation links translation to stress responses in Saccharomyces cerevisiae

2015 ◽  
Vol 26 (2) ◽  
pp. 270-282 ◽  
Author(s):  
Jadyn R. Damon ◽  
David Pincus ◽  
Hidde L. Ploegh
Keyword(s):  
Gene Expression ◽  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
Elevated Temperature ◽  
Heat Shock ◽  
Stress Responses ◽  
Wild Type ◽  
Trna Modifications ◽  
Shock Response ◽  
Tightly Coupled

Although tRNA modifications have been well catalogued, the precise functions of many modifications and their roles in mediating gene expression are still being elucidated. Whereas tRNA modifications were long assumed to be constitutive, it is now apparent that the modification status of tRNAs changes in response to different environmental conditions. The URM1 pathway is required for thiolation of the cytoplasmic tRNAs tGluUUC, tGlnUUG, and tLysUUU in Saccharomyces cerevisiae. We demonstrate that URM1 pathway mutants have impaired translation, which results in increased basal activation of the Hsf1-mediated heat shock response; we also find that tRNA thiolation levels in wild-type cells decrease when cells are grown at elevated temperature. We show that defects in tRNA thiolation can be conditionally advantageous, conferring resistance to endoplasmic reticulum stress. URM1 pathway proteins are unstable and hence are more sensitive to changes in the translational capacity of cells, which is decreased in cells experiencing stresses. We propose a model in which a stress-induced decrease in translation results in decreased levels of URM1 pathway components, which results in decreased tRNA thiolation levels, which further serves to decrease translation. This mechanism ensures that tRNA thiolation and translation are tightly coupled and coregulated according to need.

Adaptive evolution of the heat-shock response in the Antarctic psychrophilic ciliate, Euplotes focardii: hints from a comparative determination of the hsp70 gene structure

2007 ◽  
Vol 19 (2) ◽  
pp. 239-244 ◽  
Author(s):  
Antonietta La Terza ◽  
Valerio Passini ◽  
Sabrina Barchetta ◽  
Pierangelo Luporini
Keyword(s):  
Heat Shock ◽  
Promoter Region ◽  
Regulatory Region ◽  
Thermal Response ◽  
Transcription Activation ◽  
Hsp70 Gene ◽  
Shock Response ◽  
The Antarctic ◽  
Comparative Determination

AbstractThe Antarctic psychrophilic ciliate Euplotes focardii manifests a dramatic reduction in the activation of its hsp70 gene in response to a heat-shock, while oxidative and chemical stresses activate the transcription of this gene to appreciable extents. To investigate the genetic causes of this eccentric behaviour of E. focardii in the hsp70 gene transcription activation, we carried out a comparative structural analysis of this gene between E. focardii and another Antarctic Euplotes, E. nobilii, which manifests a psychrotrophic behaviour and an inducible thermal response. No substantial difference was detected in the organization of the hsp70 5' promoter region, both species bearing canonical regulatory cis-acting elements deputed to bind transcriptional trans-activating factors. Adenine-rich elements favouring mRNA degradation were instead detected in the hsp70 3' regulatory region of E. nobilii, but not in that of E. focardii. These observations lend further support to the hypothesis that the causes of the Euplotes focardii unresponsiveness to thermal stress resides in some structural, or functional modifications of transcriptional trans-activating factors.

scholarly journals The HSP70 heat shock response in the Antarctic fish Harpagifer antarcticus

Polar Biology ◽  
2007 ◽  
Vol 31 (2) ◽  
pp. 171-180 ◽  
Author(s):  
Melody S. Clark ◽  
Keiron P. P. Fraser ◽  
Gavin Burns ◽  
Lloyd S. Peck
Keyword(s):  
Heat Shock ◽  
Heat Shock Response ◽  
Antarctic Fish ◽  
Shock Response ◽  
The Antarctic

The heat shock response: A case study of chromatin dynamics in gene regulation

2013 ◽  
Vol 91 (1) ◽  
pp. 42-48 ◽  
Author(s):  
Sheila S. Teves ◽  
Steven Henikoff
Keyword(s):  
Gene Expression ◽  
Gene Regulation ◽  
Heat Shock ◽  
Heat Shock Response ◽  
Control Of Gene Expression ◽  
Pol Ii ◽  
Chromatin Dynamics ◽  
Regulatory Processes ◽  
Shock Response ◽  
Rate Limiting

Recent studies in transcriptional regulation using the Drosophila heat shock response system have elucidated many of the dynamic regulatory processes that govern transcriptional activation and repression. The classic view that the control of gene expression occurs at the point of RNA polymerase II (Pol II) recruitment is now giving way to a more complex outlook of gene regulation. Promoter chromatin dynamics coordinate with transcription factor binding to maintain the promoters of active genes accessible. For a large number of genes, the rate-limiting step in Pol II progression occurs during its initial elongation, where Pol II transcribes 30–50 bp and pauses for further signals. These paused genes have unique genic chromatin architecture and dynamics compared with genes where Pol II recruitment is rate limiting for expression. Further elongation of Pol II along the gene causes nucleosome turnover, a continuous process of eviction and replacement, which suggests a potential mechanism for Pol II transit along a nucleosomal template. In this review, we highlight recent insights into transcription regulation of the heat shock response and discuss how the dynamic regulatory processes involved at each transcriptional stage help to generate faithful yet highly responsive gene expression.

scholarly journals Genetic determinants of HSP70 gene expression following heat shock

2010 ◽  
Vol 19 (24) ◽  
pp. 4939-4947 ◽  
Author(s):  
Narelle Maugeri ◽  
Jayachandran Radhakrishnan ◽  
Julian C. Knight
Keyword(s):  
Gene Expression ◽  
Heat Shock ◽  
Hsp70 Gene ◽  
Genetic Determinants

Ubiquitin gene expression in Dictyostelium is induced by heat and cold shock, cadmium, and inhibitors of protein synthesis

1988 ◽  
Vol 90 (1) ◽  
pp. 51-58 ◽  
Author(s):  
A. Muller-Taubenberger ◽  
J. Hagmann ◽  
A. Noegel ◽  
G. Gerisch
Keyword(s):  
Gene Expression ◽  
Protein Synthesis ◽  
Heat Shock ◽  
Differential Expression ◽  
Dictyostelium Discoideum ◽  
Heat Shock Response ◽  
Cold Shock ◽  
Multifunctional Protein ◽  
Cadmium Treatment ◽  
Shock Response

Ubiquitin is a highly conserved, multifunctional protein, which is implicated in the heat-shock response of eukaryotes. The differential expression of the multiple ubiquitin genes in Dictyostelium discoideum was investigated under various stress conditions. Growing D. discoideum cells express four major ubiquitin transcripts of sizes varying from 0.6 to 1.9 kb. Upon heat shock three additional ubiquitin mRNAs of 0.9, 1.2 and 1.4 kb accumulate within 30 min. The same three transcripts are expressed in response to cold shock or cadmium treatment. Inhibition of protein synthesis by cycloheximide leads to a particularly strong accumulation of the larger ubiquitin transcripts, which code for polyubiquitins. Possible mechanisms regulating the expression of ubiquitin transcripts upon heat shock and other stresses are discussed.

Thermal acclimation changes DNA-binding activity of heat shock factor 1(HSF1) in the gobyGillichthys mirabilis: implications for plasticity in the heat-shock response in natural populations

2002 ◽  
Vol 205 (20) ◽  
pp. 3231-3240 ◽  
Author(s):  
Bradley A. Buckley ◽  
Gretchen E. Hofmann
Keyword(s):  
Gene Expression ◽  
Heat Shock ◽  
Heat Shock Response ◽  
Environmental Control ◽  
Heat Shock Factor ◽  
Thermal Acclimation ◽  
Model Systems ◽  
Threshold Temperature ◽  
Heat Shock Factor 1 ◽  
Shock Response

SUMMARYThe intracellular build-up of thermally damaged proteins following exposure to heat stress results in the synthesis of a family of evolutionarily conserved proteins called heat shock proteins (Hsps) that act as molecular chaperones, protecting the cell against the aggregation of denatured proteins. The transcriptional regulation of heat shock genes by heat shock factor 1(HSF1) has been extensively studied in model systems, but little research has focused on the role HSF1 plays in Hsp gene expression in eurythermal organisms from broadly fluctuating thermal environments. The threshold temperature for Hsp induction in these organisms shifts with the recent thermal history of the individual but the mechanism by which this plasticity in Hsp induction temperature is achieved is unknown. We examined the effect of thermal acclimation on the heat-activation of HSF1 in the eurythermal teleost Gillichthys mirabilis. After a 5-week acclimation period (at 13, 21 or 28°C) the temperature of HSF1 activation was positively correlated with acclimation temperature. HSF1 activation peaked at 27°C in fish acclimated to 13°C, at 33°C in the 21°C group, and at 36°C in the 28°C group. Concentrations of both HSF1 and Hsp70 in the 28°C group were significantly higher than in the colder acclimated fish. Plasticity in HSF1 activation may be important to the adjustable nature of the heat shock response in eurythermal organisms and the environmental control of Hsp gene expression.

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