Photosynthesis and Heat Response of the Green Alga Micrasterias denticulata (Desmidiaceae)

1999 ◽  
Vol 54 (7-8) ◽  
pp. 508-516 ◽  
Author(s):  
Dagmar Weiss ◽  
Cornelius Ltitz ◽  
Ursula Lütz-Meindl
Keyword(s):  
Heat Shock ◽  
Green Alga ◽  
Cell Shape ◽  
Incubation Temperature ◽  
Cultivation Temperature ◽  
Division Rate ◽  
Heat Shocks ◽  
Micrasterias Denticulata ◽  
Cell Shape Formation ◽  
Photosynthesis And Respiration

Abstract Cells of the green alga Micrasterias denticulata cultivated at 15 °C, 20 °C or 25 °C were exposed to heat shocks at different temperatures (30 -40 °C) for varying duration ( 5 - 90 m in). Cell pattern formation, division rate as well as photosynthesis and respiration by measuring oxygen production and consumption have been studied. The degree of cell shape malformations was found dependent on the preceding cultivation temperature along with the mode of the heat shock. Cells cultivated at 15 °C and 20 °C could counteract a 90 min heat shock at 35 °C much better than those cultivated at 25 °C, which was seen by a less reduced young semicell. Cells cultivated at 15 °C and 25 °C reveal a reduced division activity compared to those grown at 20 °C even with a marked retardation when affected by a preceding heat shock. Photosynthesis and the level of plastid pigments (carotenoids, chlorophylls, β-carotene, lutein) of controls determined by HPLC analysis reached a plateau after about 26 days when starting with 22-day old cultures. Photosynthesis and respiration were determined in a range between 15 °C and 40 °C in defined Micrasterias cell cultures of about this age (cultivation temperature 15 °C, 20 °C or 25 °C). Both processes rose steadily with increasing temperature starting with 15 °C and reached peaks between 30 °C and 32 °C, followed by a considerable drop when increasing the incubation temperature up to 40 °C. The experiments reveal that primary processes of energy formation and consumption are much less affected by temperature influences than cell shape formation and division rate

scholarly journals Transformation of the aryl hydrocarbon receptor to a DNA-binding form is accompanied by release of the 90 kDa heat-shock protein and increased affinity for 2,3,7,8-tetrachlorodibenzo-p-dioxin

1993 ◽  
Vol 294 (1) ◽  
pp. 95-101 ◽  
Author(s):  
E C Henry ◽  
T A Gasiewicz
Keyword(s):  
Heat Shock ◽  
Dna Binding ◽  
Heat Shock Protein ◽  
Aryl Hydrocarbon Receptor ◽  
Incubation Temperature ◽  
Binding Affinities ◽  
Aryl Hydrocarbon ◽  
Molecular Events ◽  
Binding Forms ◽  
Tetrachlorodibenzo P Dioxin

The binding of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to the aryl hydrocarbon receptor (AhR) elicits a sequence of poorly defined molecular events that ultimately yield a heteromeric transformed AhR that is active as a transcription factor. We have previously developed a model of the ligand-initiated transformation of the AhR to the DNA-binding state based on characterization of several forms of the AhR with respect to their physicochemical properties and DNA-binding affinities. The present studies were designed to determine whether, and at what stage, this process of transformation alters the receptor's affinity for TCDD. In rat hepatic cytosol, approx. 10% of the TCDD specifically bound to the AhR rapidly dissociated (t1/2 approximately 1 h), while the remainder was only slowly dissociable (t1/2 approximately 70 h). The isolated DNA-binding forms of the receptor (monomeric and transformed) bound TCDD very tightly (t1/2 > 100 h), whereas TCDD was dissociable from the non-DNA-binding receptor form(s). A lower incubation temperature (0-4 degrees C) and the presence of molybdate partially stabilized the non-DNA-binding fraction of the TCDD.receptor complex and also enhanced TCDD dissociation in crude cytosol. Immunoprecipitation of the different AhR forms with an anti-AhR antibody and immunoblotting with antibody to the 90 kDa heat-shock protein (hsp90) demonstrated that hsp90 was associated with the unoccupied receptor complex as well as with a fraction of the non-DNA-binding TCDD.receptor complex; isolated DNA-binding forms did not contain detectable hsp90. We conclude that while hsp90 remains associated with the AhR, TCDD is readily dissociable; following release of hsp90, however, TCDD becomes very tightly bound, and remains so upon completion of transformation.

scholarly journals Mitochondrial responses towards intermittent heat shocks in the Eastern Oyster, Crassostrea virginica

2021 ◽  
Author(s):  
Georges Hraoui ◽  
Sophie Breton ◽  
Gilles Miron ◽  
Luc H. Boudreau ◽  
Florence Hunter-Manseau ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Heat Shock ◽  
Crassostrea Virginica ◽  
Heat Waves ◽  
Physiological Stress ◽  
Eastern Oyster ◽  
Emission Rates ◽  
Mitochondrial Functions ◽  
Heat Shocks ◽  
Single Stress

Frequent heat waves caused by climate change can cause physiological stress in many animals, particularly in sessile ectotherms such as bivalves. Most studies characterizing thermal stress in bivalves focus on evaluating the responses to a single stress event. This does not accurately reflect the reality faced by bivalves which are often subject to intermittent heat waves. Here, we investigated the effect of intermittent heat stress on mitochondrial functions of Eastern oyster Crassostrea virginica which play a key role in setting ectotherms’ thermal tolerance. Specifically, we measured changes in mitochondrial oxygen consumption and H2O2 emission rates before, during and after intermittent 7.5°C heat shocks in oysters acclimated to 15°C and 22.5°C. Our results showed that oxygen consumption was impaired following the first heat shock at both acclimation temperatures. After the second heat shock, results for oysters acclimated to 15°C indicated a return to normal. However, oysters acclimated to 22.5°C struggled more with the compounding effects of intermittent heat shocks as denoted with an increase contribution of FAD-linked substrates to mitochondrial respiration as well as high levels of H2O2 emission rates. However, both acclimated populations showed signs of potential recovery ten days after the second heat shock, reflecting a surprising resilience to heat waves by C. virginica. Thus, this study highlights the important role of acclimation in oyster's capacity to weather intermittent heat shock.

Heat shock-induced alterations in phosphorylation of the largest subunit of RNA polymerase II as revealed by monoclonal antibodies CC-3 and MPM-2

1999 ◽  
Vol 77 (4) ◽  
pp. 367-374 ◽  
Author(s):  
Sébastien B Lavoie ◽  
Alexandra L Albert ◽  
Alain Thibodeau ◽  
Michel Vincent
Keyword(s):  
Heat Shock ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Transcriptional Activity ◽  
Phosphorylation Sites ◽  
Stress Genes ◽  
Terminal Domain ◽  
Carboxy Terminal Domain ◽  
Heat Shocks ◽  
Carboxy Terminal

The phosphorylation of the carboxy-terminal domain of the largest subunit of RNA polymerase II plays an important role in the regulation of transcriptional activity and is also implicated in pre-mRNA processing. Different stresses, such as a heat shock, induce a marked alteration in the phosphorylation of this domain. The expression of stress genes by RNA polymerase II, to the detriment of other genes, could be attributable to such modifications of the phosphorylation sites. Using two phosphodependent antibodies recognizing distinct hyperphosphorylated forms of RNA polymerase II largest subunit, we studied the phosphorylation state of the subunit in different species after heat shocks of varying intensities. One of these antibodies, CC-3, preferentially recognizes the carboxy-terminal domain of the largest subunit under normal conditions, but its reactivity is diminished during stress. In contrast, the other antibody used, MPM-2, demonstrated a strong reactivity after a heat shock in most species studied. Therefore, CC-3 and MPM-2 antibodies discriminate between phosphoisomers that may be functionally different. Our results further indicate that the pattern of phosphorylation of RNA polymerase II in most species varies in response to environmental stress.Key words: RNA polymerase II, heat shock, phosphorylation, CC-3, MPM-2.

Preferential deadenylation of Hsp70 mRNA plays a key role in regulating Hsp70 expression in Drosophila melanogaster

1994 ◽  
Vol 14 (6) ◽  
pp. 3646-3659
Author(s):  
R P Dellavalle ◽  
R Petersen ◽  
S Lindquist
Keyword(s):  
Drosophila Melanogaster ◽  
Heat Shock ◽  
Rna Processing ◽  
Hsp70 Expression ◽  
Hsp70 Mrna ◽  
Mild Heat ◽  
Endonucleolytic Cleavage ◽  
Heat Shocks ◽  
Low Efficiency ◽  
Hsp70 Synthesis

Following a standard heat shock, approximately 40% of Hsp70 transcripts in Drosophila melanogaster lack a poly(A) tail. Since heat shock disrupts other aspects of RNA processing, this observation suggested that heat might disrupt polyadenylation as well. We find, however, that as the temperature is increased a larger fraction of Hsp70 RNA is polyadenylated. Poly(A)-deficient Hsp70 RNAs arise not from a failure in polyadenylation but from the rapid and selective removal of poly(A) from previously adenylated transcripts. Poly(A) removal is highly regulated: poly(A) is (i) removed much more rapidly from Hsp70 RNAs than from Hsp23 RNAs, (ii) removed more rapidly after mild heat shocks than after severe heat shocks, and (iii) removed more rapidly after a severe heat shock if cells have first been conditioned by a mild heat treatment. Poly(A) seems to be removed by simple deadenylation rather than by endonucleolytic cleavage 5' of the adenylation site. During recovery from heat shock, deadenylation is rapidly followed by degradation. In cells maintained at high temperatures, however, the two processes are uncoupled and Hsp70 RNAs are deadenylated without being degraded. These deadenylated mRNAs are translated with low efficiency. Deadenylation therefore allows Hsp70 synthesis to be repressed even when degradation of the mRNA is blocked. Poly(A) tail shortening appears to play a key role in regulating Hsp70 expression.

scholarly journals THE RELATIONSHIP BETWEEN DEOXYRIBONUCLEIC ACID REPLICATION AND CELL DIVISION IN HEAT-SYNCHRONIZED TETRAHYMENA

1970 ◽  
Vol 46 (3) ◽  
pp. 533-543 ◽  
Author(s):  
William R. Jeffery ◽  
Kenneth D. Stuart ◽  
Joseph Frankel
Keyword(s):  
Cell Division ◽  
Heat Shock ◽  
Dna Synthesis ◽  
Deoxyribonucleic Acid ◽  
Heat Shock Treatment ◽  
Heat Shocks ◽  
Prolonged Heat ◽  
S Period ◽  
C 50 ◽  
The Relationship

The effect of supraoptimal temperature on macronuclear DNA synthesis in Tetrahymena was studied by radioautography during prolonged heat and heat-shock synchronization treatments. Prolonged heat treatments (34°C) delayed the initiation of S, but did not appreciably delay DNA synthesis in progress. Return to optimal temperature (28°C) 50 or 100 min later resulted in initiation of S, in delayed cells, at a rate greater than in controls. During the synchronization treatment, most cells were unable to enter S during a heat shock, but initiated S with a slight delay during the following intershock period. These cells were not appreciably delayed in completion of S by subsequent heat shocks. Supraoptimal temperature appears to affect the DNA synthetic cycle near the G1 to S transition. Cells subjected to the heat-shock treatment in early G1 all participated in one S period, and many underwent a succession of two S periods. DNA synthesis occurred in about 50% of the cells between EST and the first synchronous division, with the likelihood of DNA synthesis becoming greater the longer the interval between these two events. In some cells no detectable DNA synthesis occurred between EST and the second synchronous division. It was concluded that a precise temporal alternation of DNA replication and cell division is not obligatory in Tetrahymena.

scholarly journals P transposons controlled by the heat shock promoter.

1986 ◽  
Vol 6 (5) ◽  
pp. 1640-1649 ◽  
Author(s):  
H Steller ◽  
V Pirrotta
Keyword(s):  
Heat Shock ◽  
Germ Line ◽  
Fusion Gene ◽  
P Element ◽  
Translational Efficiency ◽  
Heat Shock Promoter ◽  
P Elements ◽  
Heat Shocks ◽  
Neomycin Resistance ◽  
Heat Shock Induction

We have transformed Drosophila melanogaster with modified P-element transposons, which express the transposase function from the heat-inducible hsp70 heat shock promoter. The Icarus transposon, which contains a direct hsp70-P fusion gene, behaved like a very active autonomous P element even before heat shock induction. Although heat shock led to abundant somatic transcription, transposition of the Icarus element was confined to germ line cells. To reduce the constitutive transposase activity observed for the Icarus element, we attenuated the translational efficiency of the transposase RNA by inserting the transposon 5 neomycin resistance gene between the hsp70 promoter and the P-element sequences. The resulting construct, called Icarus-neo, conferred resistance to G418, and its transposition was significantly stimulated by heat shock. Heat shocks applied during the embryonic or third instar larval stage had similar effects, indicating that transposition of P elements is not restricted to a certain developmental stage. Both Icarus and Icarus-neo destabilized snw in a P-cytotype background and thus at least partially overcome the repression of transposition. Our results suggest that the regulation of P-element transposition occurs at both the transcriptional and posttranscriptional levels.

Seed germination response of a potential rangeland weed Psilocaulon granulicaule to selected environmental conditions

2020 ◽  
Vol 68 (5) ◽  
pp. 363
Author(s):  
Rekha Ranaweera ◽  
Sandra L. Weller ◽  
Singarayer K. Florentine
Keyword(s):  
Water Stress ◽  
Heat Shock ◽  
Seed Germination ◽  
Management Practices ◽  
Germination Rate ◽  
Radiant Heat ◽  
Weed Species ◽  
Light Regimes ◽  
Heat Shocks ◽  
Environmental Weed

Studies show that just over 620 non-native naturalised plant species have been recorded within the Australian rangelands, some of which have a capacity to cause significant impacts on rangeland flora and grazing activity. Although Psilocaulon granulicaule (Haw.), Schwantes is listed as a highly invasive environmental weed species, there has been no previous research into its seed ecology. Therefore, this study was conducted to investigate the effects of temperature, light, pH, water stress, heat-shock, and salinity on the germination of P. granulicaule. In this study, four temperature regimes covering four different day and night temperature variations (17–7°C, 25–15°C, 30–25°C and 40–30°C) and two light regimes (12-h light–12-h dark, 24-h dark) were investigated. The effects of pH, water stress, heat-shock and salinity were investigated, using pH buffers, polyethylene glycol solutions, three heat shock events under four temperatures and a range of NaCl solutions. These tests were conducted under the identified optimum temperature range (25/15°C) and light regime for seed germination. The results showed that both temperature and photoperiod significantly influenced the germination rate, with 94.2% germination in the 25–15°C range under a 12-h light-12-h dark regime. Higher temperatures (30–40°C) reduced seed germination to <58% germination in both light regimes (57.5%, 12-h light-12-h dark; 54.17%, 24-h dark). The highest germination rates were observed in low pH solutions, high moisture levels, low heat-shocks and low salinity. The study showed that this species is sensitive to environmental factors such as temperature, light, pH, moisture, heat shock and salinity, suggesting that these factors can be used as critical indicators to guide effective management practices to address this weed problem. Given that seeds are sensitive to radiant heat, burning could be used as a tool to effectively manage this species.

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