scholarly journals The influence of nutrient availability on the thermotolerance of symbiotic dinoflagellates of family Symbiodiniaceae

2021 ◽  
Author(s):  
Evan Raymond
Keyword(s):  
Heat Stress ◽  
Nutrient Availability ◽  
Stress Responses ◽  
Nutrient Dynamics ◽  
Elevated Temperatures ◽  
Light Exposure ◽  
D1 Protein ◽  
Structural Complexity ◽  
Local Environment ◽  
Nutrient Utilization

<p><b>Coral reefs are the most biodiverse ocean ecosystems on the planet, providing essential habitat for over 25% of the world’s marine organisms. Their structural complexity and stability contribute to essential coastline defence against erosion, as well as provide billions of dollars per year in economic value in the form of tourism and artisanal fishing. Fundamental to this unique and indispensable habitat is the symbiotic relationship between cnidarian corals and algal dinoflagellates of family Symbiodiniaceae. Reef-building corals gain a crucial majority of their daily energy needs from their endosymbiotic dinoflagellates, which facilitates coral growth, reproduction and formation of the reef structure on which countless other organisms thrive. However, this symbiosis has come under threat from warming oceans as a consequence of anthropogenic climate change. Under thermal stress the cnidarian-dinoflagellate symbiosis breaks down, resulting in expulsion of the dinoflagellate (‘coral bleaching’), followed by the eventual death of the coral animal. Tolerance of elevated temperatures is known to vary among coral and Symbiodiniaceae species, and may be influenced by the interaction of nutrient availability and photosynthetic function of the endosymbiont. </b></p> <p>The aim of this thesis was to investigate photophysiological mechanisms in thermotolerant and thermally sensitive Symbiodiniaceae to determine how they are affected by thermal and nutritive stress, both in and out of symbiosis. </p> <p>Cultured Symbiodiniaceae phylotypes A4 (thermotolerant) and B2 (thermally sensitive) were subjected to high and low nutrient and temperature treatments. The photosynthetic health (quantum yield, FV/FM), rate of chloroplastic protein synthesis (D1 protein) and photophysiological response to light (NPQ) of each phylotype was monitored to determine if thermotolerance was related to nutrient utilization under heat stress. Phylotype A4 showed considerably increased D1 synthesis regardless of nutrient treatment when compared to phylotype B2, but only minor differences in FV/FM. Also, correlation between D1 concentration and FV/FM was observed in A4, but not B2 during recovery from heat stress. Responses to short term light exposure contrasted significantly between the two phylotypes under all conditions, indicating marked differences in the photophysiological apparatus. </p> <p>To examine nutrient use and thermotolerance in symbiosis, the model symbiotic anemone Aiptasia pallida (commonly Aiptasia) was inoculated with either Symbiodiniaceae species Breviolum minutum, phylotype A4 or phylotype B2. The holobionts (host and symbiont) were fed or starved for a period of six weeks and then subjected to heat stress. D1protein concentration and FV/FM was similar in all fed holobionts, regardless of symbiont type and heat treatment. Following heat stress, all starved holobionts showed extremely low concentrations of D1 protein, but comparable FV/FM, while in low temperature starved treatments, only Aiptasia hosting B. minutum showed any recovery of D1 protein. The study shows that efficiency of nutrient utilization in photosynthetic pathways is not necessarily an indicator of thermotolerance, nor does it dictate the ability of the symbiont to confer physiological benefits to the host under conditions of heat or nutrient stress. Rather, host-symbiont pairings most likely reflect responses to external pressures dictated by the local environment. The implications of the physiological disparities between the Symbiodiniaceae types tested are discussed in the context of environmental adaptations and host-symbiont nutrient dynamics. The complexity of symbiotic interactions highlighted by this study reinforces the imperative necessity of further investigations into cnidarian-dinoflagellate symbioses, particularly in regard to thermotolerance and photophysiology. Only through understanding the physiological effects of rising ocean temperatures on this essential partnership can we begin the work of protecting the coral reef habitat for future generations.</p>

scholarly journals The influence of nutrient availability on the thermotolerance of symbiotic dinoflagellates of family Symbiodiniaceae

2021 ◽  
Author(s):  
Evan Raymond
Keyword(s):  
Heat Stress ◽  
Nutrient Availability ◽  
Stress Responses ◽  
Nutrient Dynamics ◽  
Elevated Temperatures ◽  
Light Exposure ◽  
D1 Protein ◽  
Structural Complexity ◽  
Local Environment ◽  
Nutrient Utilization

<p><b>Coral reefs are the most biodiverse ocean ecosystems on the planet, providing essential habitat for over 25% of the world’s marine organisms. Their structural complexity and stability contribute to essential coastline defence against erosion, as well as provide billions of dollars per year in economic value in the form of tourism and artisanal fishing. Fundamental to this unique and indispensable habitat is the symbiotic relationship between cnidarian corals and algal dinoflagellates of family Symbiodiniaceae. Reef-building corals gain a crucial majority of their daily energy needs from their endosymbiotic dinoflagellates, which facilitates coral growth, reproduction and formation of the reef structure on which countless other organisms thrive. However, this symbiosis has come under threat from warming oceans as a consequence of anthropogenic climate change. Under thermal stress the cnidarian-dinoflagellate symbiosis breaks down, resulting in expulsion of the dinoflagellate (‘coral bleaching’), followed by the eventual death of the coral animal. Tolerance of elevated temperatures is known to vary among coral and Symbiodiniaceae species, and may be influenced by the interaction of nutrient availability and photosynthetic function of the endosymbiont. </b></p> <p>The aim of this thesis was to investigate photophysiological mechanisms in thermotolerant and thermally sensitive Symbiodiniaceae to determine how they are affected by thermal and nutritive stress, both in and out of symbiosis. </p> <p>Cultured Symbiodiniaceae phylotypes A4 (thermotolerant) and B2 (thermally sensitive) were subjected to high and low nutrient and temperature treatments. The photosynthetic health (quantum yield, FV/FM), rate of chloroplastic protein synthesis (D1 protein) and photophysiological response to light (NPQ) of each phylotype was monitored to determine if thermotolerance was related to nutrient utilization under heat stress. Phylotype A4 showed considerably increased D1 synthesis regardless of nutrient treatment when compared to phylotype B2, but only minor differences in FV/FM. Also, correlation between D1 concentration and FV/FM was observed in A4, but not B2 during recovery from heat stress. Responses to short term light exposure contrasted significantly between the two phylotypes under all conditions, indicating marked differences in the photophysiological apparatus. </p> <p>To examine nutrient use and thermotolerance in symbiosis, the model symbiotic anemone Aiptasia pallida (commonly Aiptasia) was inoculated with either Symbiodiniaceae species Breviolum minutum, phylotype A4 or phylotype B2. The holobionts (host and symbiont) were fed or starved for a period of six weeks and then subjected to heat stress. D1protein concentration and FV/FM was similar in all fed holobionts, regardless of symbiont type and heat treatment. Following heat stress, all starved holobionts showed extremely low concentrations of D1 protein, but comparable FV/FM, while in low temperature starved treatments, only Aiptasia hosting B. minutum showed any recovery of D1 protein. The study shows that efficiency of nutrient utilization in photosynthetic pathways is not necessarily an indicator of thermotolerance, nor does it dictate the ability of the symbiont to confer physiological benefits to the host under conditions of heat or nutrient stress. Rather, host-symbiont pairings most likely reflect responses to external pressures dictated by the local environment. The implications of the physiological disparities between the Symbiodiniaceae types tested are discussed in the context of environmental adaptations and host-symbiont nutrient dynamics. The complexity of symbiotic interactions highlighted by this study reinforces the imperative necessity of further investigations into cnidarian-dinoflagellate symbioses, particularly in regard to thermotolerance and photophysiology. Only through understanding the physiological effects of rising ocean temperatures on this essential partnership can we begin the work of protecting the coral reef habitat for future generations.</p>

scholarly journals Heat Stress Impact on Yield and Composition of Quinoa Straw under Mediterranean Field Conditions

Plants ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 955
Author(s):  
Javier Matías ◽  
Verónica Cruz ◽  
María Reguera
Keyword(s):  
Heat Stress ◽  
High Temperatures ◽  
Stress Responses ◽  
Elevated Temperatures ◽  
Chenopodium Quinoa ◽  
Field Conditions ◽  
Change Scenario ◽  
Straw Yield ◽  
Feed Value ◽  
Smart Agriculture

Quinoa (Chenopodium quinoa Willd.) is receiving increasing attention globally due to the high nutritional value of its seeds, and the ability of this crop to cope with stress. In the current climate change scenario, valorization of crop byproducts is required to support a climate-smart agriculture. Furthermore, research works characterizing and evaluating quinoa stems and their putative uses are scarce. In this work, straw yield and composition, and the relative feed value of five quinoa varieties, were analyzed in two consecutive years (2017–2018) under field conditions in Southwestern Europe. High temperatures were recorded during the 2017 growing season resulting in significantly decreased straw yield and improved feed value, associated with compositional changes under elevated temperatures. Crude protein, ash, phosphorus, and calcium contents were higher under high temperatures, whereas fiber contents decreased. The relative feed value was also higher in 2017 and differed among varieties. Differences among varieties were also found in straw yield, and contents of phosphorus, potassium, and calcium. Overall, the results presented here support a sustainable quinoa productive system by encouraging straw valorization and shedding light on the mechanisms underlying heat-stress responses in this crop.

scholarly journals The Hsp60 Protein of Helicobacter Pylori Exhibits Chaperone and ATPase Activities at Elevated Temperatures

BioChem ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 19-25
Author(s):  
Jose A. Mendoza ◽  
Julian L. Ignacio ◽  
Christopher M. Buckley
Keyword(s):  
Helicobacter Pylori ◽  
Heat Stress ◽  
Molecular Chaperone ◽  
Elevated Temperatures ◽  
Citrate Synthase ◽  
Gastric Epithelium ◽  
Acidic Conditions ◽  
H Pylori ◽  
Induced Aggregation ◽  
Hydrolysis Of

The heat-shock protein, Hsp60, is one of the most abundant proteins in Helicobacter pylori. Given its sequence homology to the Escherichia coli Hsp60 or GroEL, Hsp60 from H. pylori would be expected to function as a molecular chaperone in this organism. H. pylori is a type of bacteria that grows on the gastric epithelium, where the pH can fluctuate between neutral and 4.5, and the intracellular pH can be as low as 5.0. We previously showed that Hsp60 functions as a chaperone under acidic conditions. However, no reports have been made on the ability of Hsp60 to function as a molecular chaperone under other stressful conditions, such as heat stress or elevated temperatures. We report here that Hsp60 could suppress the heat-induced aggregation of the enzymes rhodanese, malate dehydrogenase, citrate synthase, and lactate dehydrogenase. Moreover, Hsp60 was found to have a potassium and magnesium-dependent ATPase activity that was stimulated at elevated temperatures. Although, Hsp60 was found to bind GTP, the hydrolysis of this nucleotide could not be observed. Our results show that Hsp60 from H. pylori can function as a molecular chaperone under conditions of heat stress.

The neglected other half ‐ role of the pistil in plant heat stress responses

2021 ◽  
Author(s):  
Yuanyuan Wang ◽  
S.M. Impa ◽  
Ramanjulu Sunkar ◽  
S.V. Krishna Jagadish
Keyword(s):  
Heat Stress ◽  
Stress Responses

scholarly journals Transcriptome analysis of two contrasting genotypes of pearl millet to gain insight into heat stress responses

2020 ◽  
Author(s):  
Albert Maibam ◽  
Sunil Nigombam ◽  
Harinder Vishwakarma ◽  
Showkat Ahmad Lone ◽  
Kishor Gaikwad ◽  
...  
Keyword(s):  
Heat Stress ◽  
Pearl Millet ◽  
Stress Responses ◽  
Simple Sequence Repeats ◽  
Pennisetum Glaucum ◽  
Average Length ◽  
Gc Content ◽  
Functional Markers ◽  
Sequencing Data ◽  
Simple Sequence

Abstract Background Pennisetum glaucum (L.) R. Br. is mainly grown in arid and semi-arid regions. Being naturally tolerant to various adverse condtitions, it is a good biological resource for deciphering the molecular basis of abiotic stresses such as heat stress in plants but limited studies have been carried out till date to this effect. Here, we performed RNA-sequencing from the leaf of two contrasting genotypes of pearl millet (841-B and PPMI-69) subjected to heat stress (42 °C for 6 h). Results Over 274 million high quality reads with an average length of 150 nt were generated. Assembly was carried out using trinity, obtaining 47,310 unigenes having an average length of 1254 nucleotides, N50 length of 1853 nucleotides and GC content of 53.11%. Blastx resulted in annotation of 35,628 unigenes and functional classification showed 15,950 unigenes designated to 51 Gene Ontology terms, 13,786 unigenes allocated to 23 Clusters of Orthologous Groups and 4,255 unigenes distributed into 132 functional KEGG pathways. 12,976 simple sequence repeats were identified from 10,294 unigenes for the development of functional markers. A total of 3,05,759 SNPs were observed in the transcriptome data. Out of 2,301 differentially expressed genes, 10 potential candidates genes were selected based on log2 fold change and adjusted p-value parameters for their differential gene expression by qRT-PCR. Conclusions The dynamic expression changes in two genotypes of P. glaucum reflect transcriptome regulation of signaling pathways in heat stress response. In order to develop genetic markers, 12,976 simple sequence repeats (SSRs) were identified. The sequencing data generated in this study shall serve as an important resource for further research in the area of crop biotechnology.

scholarly journals Absence of the Outer Membrane Phospholipase A Suppresses the Temperature-Sensitive Phenotype of Escherichia coli degPMutants and Induces the Cpx and ςE Extracytoplasmic Stress Responses

2001 ◽  
Vol 183 (18) ◽  
pp. 5230-5238 ◽  
Author(s):  
Geoffrey R. Langen ◽  
Jill R. Harper ◽  
Thomas J. Silhavy ◽  
S. Peter Howard
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Stress Responses ◽  
Elevated Temperatures ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Phospholipase A ◽  
Temperature Sensitive ◽  
Outer Membrane Phospholipase A ◽  
Temperature Sensitive Phenotype

ABSTRACT DegP is a periplasmic protease that is a member of both the ςE and Cpx extracytoplasmic stress regulons ofEscherichia coli and is essential for viability at temperatures above 42°C. [U-14C]acetate labeling experiments demonstrated that phospholipids were degraded indegP mutants at elevated temperatures. In addition, chloramphenicol acetyltransferase, β-lactamase, and β-galactosidase assays as well as sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis indicated that large amounts of cellular proteins are released from degP cells at the nonpermissive temperature. A mutation in pldA, which encodes outer membrane phospholipase A (OMPLA), was found to rescue degPcells from the temperature-sensitive phenotype. pldA degP mutants had a normal plating efficiency at 42°C, displayed increased viability at 44°C, showed no degradation of phospholipids, and released far lower amounts of cellular protein to culture supernatants. degP and pldA degP mutants containing chromosomal lacZ fusions to Cpx and ςE regulon promoters indicated that both regulons were activated in the pldA mutants. The overexpression of the envelope lipoprotein, NlpE, which induces the Cpx regulon, was also found to suppress the temperature-sensitive phenotype ofdegP mutants but did not prevent the degradation of phospholipids. These results suggest that the absence of OMPLA corrects the degP temperature-sensitive phenotype by inducing the Cpx and ςE regulons rather than by inactivating the phospholipase per se.

Exogenously-Supplied Trehalose Provides Better Protection for D1 Protein in Winter Wheat under Heat Stress

2018 ◽  
Vol 65 (1) ◽  
pp. 115-122 ◽  
Author(s):  
Y. Luo ◽  
W. Wang ◽  
Y. Z. Fan ◽  
Y. M. Gao ◽  
D. Wang
Keyword(s):  
Heat Stress ◽  
Winter Wheat ◽  
D1 Protein

N6-methyladenosine modification modulate in the heat stress of sheep (Ovis aries)

2019 ◽  
Author(s):  
Zengkui Lu ◽  
Huihua Wang ◽  
Youji Ma ◽  
Mingxing Chu ◽  
Kai Quan ◽  
...  
Keyword(s):  
Heat Stress ◽  
Signaling Pathways ◽  
Stress Responses ◽  
Large Scale ◽  
Ovis Aries ◽  
Stop Codons ◽  
Coding Regions ◽  
Mrna Methylation ◽  
Response To Stress ◽  
And Control

Abstract Background: Intensive and large-scale development of the sheep industry and increases in global temperature are increasingly exposing sheep to heat stress. N6-methyladenosine (m6A) mRNA methylation varies in response to stress, and can link external stress with complex transcriptional and post-transcriptional processes. However, no m6A mRNA methylation map has been obtained for sheep, nor is it known what effect this has on regulating heat stress in sheep. Results: A total of 8,306 and 12,958 m6A peaks were detected in heat stress and control groups, respectively, with 2,697 and 5,494 genes associated with each. Peaks were mainly enriched in coding regions and near stop codons with classical RRACH motifs. Methylation levels of heat stress and control sheep were higher near stop codons, although methylation was significantly lower in heat stress sheep. GO revealed that differential m6A-containing genes were mainly enriched in the nucleus and were involved in several stress responses and substance metabolism processes. KEGG pathway analysis found that differential m6A-containing genes were significantly enriched in Rap1, FoxO, MAPK, and other signaling pathways of the stress response, and TGF-beta, AMPK, Wnt, and other signaling pathways involved in fat metabolism. These m6A-modified genes were moderately expressed in both heat stress and control sheep, and the enrichment of m6A modification was significantly negatively correlated with gene expression. Conclusions: Our results showed that m6A mRNA methylation modifications regulate heat stress in sheep, and it also provided a new way for the study of animal response to heat stress.

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