Bettina Zeis - Academia.edu (original) (raw)

Papers by Bettina Zeis

BMC Physiology, Apr 21, 2009

Background: Freshwater planktonic crustaceans of the genus Daphnia show a remarkable plasticity t... more Background: Freshwater planktonic crustaceans of the genus Daphnia show a remarkable plasticity to cope with environmental changes in oxygen concentration and temperature. One of the key proteins of adaptive gene control in Daphnia pulex under hypoxia is hemoglobin (Hb), which increases in hemolymph concentration by an order of magnitude and shows an enhanced oxygen affinity due to changes in subunit composition. To explore the full spectrum of adaptive protein expression in response to low-oxygen conditions, two-dimensional gel electrophoresis and mass spectrometry were used to analyze the proteome composition of animals acclimated to normoxia (oxygen partial pressure [Po 2 ]: 20 kPa) and hypoxia (Po 2 : 3 kPa), respectively. Results: The comparative proteome analysis showed an up-regulation of more than 50 protein spots under hypoxia. Identification of a major share of these spots revealed acclimatory changes for Hb, glycolytic enzymes (enolase), and enzymes involved in the degradation of storage and structural carbohydrates (e.g. cellubiohydrolase). Proteolytic enzymes remained constitutively expressed on a high level. Conclusion: Acclimatory adjustments of the D. pulex proteome to hypoxia included a strong induction of Hb and carbohydrate-degrading enzymes. The scenario of adaptive protein expression under environmental hypoxia can be interpreted as a process to improve oxygen transport and carbohydrate provision for the maintenance of ATP production, even during short episodes of tissue hypoxia requiring support from anaerobic metabolism.

Journal of Thermal Biology, Oct 1, 2004

Thermal acclimation in Daphnia magna was studied on various levels to test the recent ''oxygen-li... more Thermal acclimation in Daphnia magna was studied on various levels to test the recent ''oxygen-limited thermal tolerance'' hypothesis. Preference behaviour in a thermal gradient was determined by both, ambient temperature and corresponding oxygen concentration. Swimming activity depended on aerobic energy provision and reflected the match or mismatch of oxygen supply and energy demand at different ambient temperatures. Thermal acclimation modified both types of behaviour and more slightly heat tolerance. Perfusion and haemoglobin properties turned out to be central control variables to adapt oxygen transport to varying energy demands at different ambient temperatures. Exceptional advantages of Daphnia as an experimental model organism allowed to confirm on a behavioural, physiological and biochemical level that thermal acclimation is strongly based on the adaptation of oxygen transport allowing unidirectional shifts of the thermal tolerance range to warmer or colder temperatures.

Comparative Biochemistry and Physiology B, Aug 1, 2021

Zooplankton organisms face a variable food supply in their habitat. Metabolic adjustments during ... more Zooplankton organisms face a variable food supply in their habitat. Metabolic adjustments during periods of starvation were analysed from changes in metabolite level to gene expression in the microcrustacean Daphnia pulex during starvation. The animals exploited their carbohydrate stores first, but their lipid and protein reserves were also degraded, albeit more slowly. Glycogenolysis and probably gluconeogenesis led to hyperglycaemia after 16 h of starvation. The concentration of α-ketoglutarate and the rate of oxygen consumption also reached maxima during this period. Nuclear HIF-1α levels and α-ketoglutarate concentration showed inverse correlation. Effects of this 2-oxoacid on prolyl hydroxylase activity, HIF-1α stability and the role of this transcription factor in the changes of the expression level of several putatively HIF-1-mediated metabolic genes are discussed. Transcriptome profiling via RNA-Seq revealed a downregulation of genes for protein biosynthesis and an upregulation of genes for carbohydrate metabolism during starvation. Thus, the adjustments of energy metabolism in response to food deprivation were quantified from the level of metabolites, signal transduction and gene expression, and possible connections of the respective dynamics of observed changes were analysed.

Comparative Biochemistry and Physiology B, Jun 1, 2019

Optimizing physiological functions at different temperatures includes shifts in the lipid composi... more Optimizing physiological functions at different temperatures includes shifts in the lipid composition of ectothermic animals. These shifts may be associated with changes in lipid peroxidation in response to oxidative stress, because lipids differ in their susceptibility to oxidative damage. Polyunsaturated fatty acids (PUFA) are particular prone to peroxidation. Here, we analyzed changes in the fatty acid composition, cholesterol content and the level of oxidative damage as thiobarbituric reactive substances (TBARS) in Daphnia magna as a function of acclimation temperature. The total fatty acid content was highest in cold-acclimated animals. The relative share of most PUFA decreased with increasing acclimation temperature. In contrast, the contribution of saturated and monounsaturated fatty acids (SFA and MUFA) increased with acclimation temperature, although the latter to a lower extent. Cholesterol content remained unchanged. The level of oxidative damage was lowest in animals reared at warm temperatures, most likely reflecting their lowest content of PUFA. Heat exposure (1 h at 33°C) caused the highest increase in lipid peroxidation in cold-acclimated animals, containing more PUFA. Our data suggest that cold-induced adjustments in the body lipid composition increase the vulnerability of zooplankton to heat-induced oxidative stress. In particular, animals performing diel vertical migration may be highly susceptible to temperature-induced lipid damage.

Physiological and Biochemical Zoology, May 1, 2005

Oxygen preference of the planktonic crustacean Daphnia magna was observed within an oxygen gradie... more Oxygen preference of the planktonic crustacean Daphnia magna was observed within an oxygen gradient. Long-term acclimation to specific oxygen conditions determined the preferred oxygen tension. Animals from hypoxic acclimation stayed in oxygen-poor water at first. They chose oxygen tensions above the critical partial pressure, thus maintaining aerobic energy supply, but they avoided higher oxygen concentrations. However, they gradually took more oxygen-rich positions within 2 d. Animals from severe hypoxic and hyperoxic acclimation showed stenoxic behavior. Specimens raised in moderately hypoxic or normoxic medium spread out more widely in the oxygen gradient (euryoxic behavior). The possible role of hemoglobin and antioxidant defense capacity limiting the animals&amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; distribution at low or high oxygen concentrations, respectively, is discussed. In tests with mixed groups of D. magna from opposing oxygen acclimation conditions, the animals clustered at intermediate oxygen conditions. However, the acclimation condition of the major group was found to determine the position taken within the gradient to a greater extent. Selected oxygen tensions were closer to the preference values of the larger group, yet the influence of the minority prevented the majority in heterogeneous groups from taking their originally determined preference position. Thus, aggregation behavior interfered with the acclimation-dependent oxygen preference behavior.

Acta Physiologica Scandinavica, Nov 1, 2004

The pathway for oxygen, the control of oxygen transport and the role of haemoglobin expression fo... more The pathway for oxygen, the control of oxygen transport and the role of haemoglobin expression for the physiological adaptation to different oxygen and temperature conditions were studied in the ecological model organism Daphnia magna. Ventilation of the inner walls of the carapace as the main gas exchange area as well as of the embryos in the brood pouch are controlled, oxygen-dependent processes. The P O 2-dependent increase of heart rate as well as perfusion rate during short-term, progressive hypoxia improves the circulatory oxygen transport within the body. The regulation of haemoglobin (Hb) expression is the central mechanism for a medium-term adaptation to hypoxia. Genetic control elements and oxygen conditions near the two Hb synthesis sites (fat cells, epipodite epithelial cells) determine, which types of Hb subunits and, accordingly, hetero-multimeric Hb macromolecules are produced. One synthesis site may respond mainly to internal, the other one to external oxygen conditions. Depending on environmental condition, either higher quantities of macromolecules of unchanged functionality (P 50) or increasing amounts of macromolecules with higher oxygen affinity are synthesized. The Hb subunit DmHbA is probably of considerable importance for this functional change. The physiological benefits of haemoglobin in Daphnia are discussed. Physiological adaptation of Daphnia to different temperatures is also related to the control of oxygen transport processes with the regulation of haemoglobin expression again as a central mechanism.

Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, Sep 1, 2008

Freshwater Biology, Aug 1, 2007

1. In a combined field and laboratory study, seasonal relationships between water temperature and... more 1. In a combined field and laboratory study, seasonal relationships between water temperature and oxygen content, genetic structure (composition of MultiLocus Genotypes, MLGs) of a Daphnia assemblage (D. galeata-hyalina hybrid species complex), and the physiological properties of clones of frequent MLGs were studied. In accordance with the oxygen-limited thermal tolerance hypothesis, essential physiological variables of oxygen transport and supply were measured within the tolerable temperature range. 2. A few MLGs (types T1-T4) were frequent during early spring and late autumn at surface temperatures below 10°C. Clones of T1-T4 showed a low tolerance towards higher temperatures (above 20°C) and a high phenotypic plasticity under thermal acclimation in comparison to clones derived from frequent MLGs from later seasons, and stored highmedium quantities of carbohydrates at 12 and 18°C. 3. Another MLG (T6) succeeded the MLGs T1-T4. T6 was frequent over most of the year at temperatures above 10°C and below 20°C. A clone derived from T6 exhibited a high tolerance towards warm temperatures and a more restricted phenotypic plasticity. It stored high-medium quantities of carbohydrates at 12, 18 and 24°C and showed a high capacity for acclimatory adjustments based on haemoglobin expression. 4. During the summer period at temperatures ‡20°C, the MLG T6 was found mainly near to the thermocline, where temperature and oxygen content were distinctly lower, and to a lesser extent in surface water. At the surface, another MLG (T19) was predominant during this period. A clone of this MLG showed a very high tolerance towards warm temperatures, minimal phenotypic plasticity, low carbohydrate stores and a high capacity for circulatory adjustments to improve oxygen transport at higher temperatures. 5. This study provides evidence for connections between the spatio-temporal genetic heterogeneity of a Daphnia assemblage and the seasonal changes of water temperature and oxygen content. The data also suggest that not only the actual temperature but also the dynamics of temperature change may influence the genetic structure of Daphnia populations and assemblages.

Journal of Experimental Zoology Part A: Ecological and Integrative Physiology, Apr 11, 2023

Limits of thermal tolerance in animal life is dependent on energy supply. Accordingly, the lowere... more Limits of thermal tolerance in animal life is dependent on energy supply. Accordingly, the lowered ATP production capacity in ectotherms at high temperatures, which arises from a mismatch between oxygen supply and demand and the consequent switch from aerobic to anaerobic metabolism, affects the thermal resistance of these animals. The anaerobic ATP production capacity depends on the functional properties of the enzymes that reduce pyruvate. Thus, the present study focused on the role of the lactate dehydrogenase (LDH) of two daphnid species for anaerobic energy production at warm temperatures and the implications for their specific heat tolerances. Daphnia magna showed a higher thermal limit (indicated by immobilization time at 37°C) than Daphnia pulex, and in both species, this limit increased with rising acclimation temperature. In contrast to D. pulex, D. magna accumulated significant amounts of lactate at higher ambient temperatures. The intensity of anaerobic metabolism was also affected by acclimation temperature. Studying the functional enzyme properties revealed altered maximal reaction rates and substrate inhibitions of the LDH suites of the two daphnid species. D. magna LDH showed a significantly lower substrate inhibition than D. pulex LDH. The LDH isoform composition and the temperature‐induced changes differed between both species. The detected qualitative modulations of the LDH suites may have resulted from differential isoform expression and different maturation processes. The species‐specific LDH characteristics imply a higher anaerobic energy production at warm temperatures in D. magna, which likely contributes to the higher heat tolerance of this species.

Journal of Experimental Zoology Part A: Ecological and Integrative Physiology

Table S2. Labeling design of the microarrays. (PDF 83Â kb)

Figure S6. Experimental design. (PDF 144Â kb)

Figure S5. Two-dimensional protein gels from the D. pulex clone M under heat-and-starvation stres... more Figure S5. Two-dimensional protein gels from the D. pulex clone M under heat-and-starvation stress. The 2D gels, which are fusion (averaged) images from a varying number (n) of gels (biological replicates, 25-30 animals each), show changes in protein expression in the D. pulex clone M after the acute exposure of control animals (20 °C, ad libitum feeding) (blue spots; n = 4) to (a) 24 h (orange spots; n = 5) or (c) 48 h (orange spots; n = 7) of heat-and-starvation stress (T = 30 °C, starvation). Red or green spot IDs mark significantly up- or downregulated proteins (t-tests, P

Figure S2. Two-dimensional protein gels from the D. pulex clone G under starvation stress. The 2D... more Figure S2. Two-dimensional protein gels from the D. pulex clone G under starvation stress. The 2D gels, which are fusion (averaged) images from a varying number (n) of gels (biological replicates, 25-30 animals each), show changes in protein expression in the D. pulex clone G after the acute exposure of control animals (20 °C, ad libitum feeding) (blue spots; n = 5) to (a) 24 h (orange spots; n = 4) or (c) 48 h (orange spots; n = 4) of starvation (T = 20 °C). Red or green spot IDs mark significantly up- or downregulated proteins (t-tests, P

Table S1. KOG-identified DEGs shared by the contrasts under acute heat stress. (PDF 125Â kb)

Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology, 2021

Physiology of the Cladocera, 2014

ABSTRACT Recent advances in genomic approaches and their increasing application to a wide range o... more ABSTRACT Recent advances in genomic approaches and their increasing application to a wide range of taxa are contributing to the rapid development of the field of physiological genomics. Understanding the relationship between organisms and their environment is central to this field that focuses on genomic exploration of the physiological mechanisms that underlie organism-environment interactions and phenotypic plasticity. Cladoceran crustaceans have long been the subject of physiological investigation and are now tractable and versatile models for physiological genomics. A wide diversity of habitats and physiologies along with the recent development of genomic tools, most notably in the genus Daphnia, make cladocerans a compelling taxonomic group to investigate the relationship between genome structure, function and physiological mechanisms in a comparative framework that will also illuminate the evolutionary processes underlying these mechanisms. In this chapter we highlight a series of case studies to illustrate the potential to use cladocerans to illuminate the physiological mechanisms that mediate the response of organisms to environmental challenges. We focus on the genus Daphnia because of the rich history in ecological, evolutionary, and physiological research on this group and the recent investigations into its ecoresponsive genome. Finally, we prospectively outline productive avenues for future investigation.

Journal of Thermal Biology, 2004

Freshwater Biology, 2007