Project description:Marker-assisted selective breeding of fish with higher levels of resistance towards specific pathogens has shown successful, but. However, the impact of host genotype on multiple pathogen infections are is still poorly investigated. This study examined the resistance in rainbow trout (Oncorhynchus mykis) towards infection with the eye fluke Diplostomum pseudospathaceum. We used genetically selected rainbow trout, carrying SNPs associated with resistance towards the parasitic ciliate Ichthyophthirius multifiliis, and exposed the fish to eye fluke cercariae. We showed that fish partly resistant to I. multifiliis were more susceptible to eye fluke invasion. Expression The expression of immune relevant genes (encoding innate and adaptive factors) was also affected as these genotypes responded less strongly to a secondary fluke infection. The complexity of genome architecture in disease resistance towards multiple pathogens is discussed. A total of 200 rainbow trout (body weight 14.3-17.7 g, body length 10.2-11.5 cm) were used for the study. Two groups of rainbow trout with high (QTL fish) and low (non-QTL fish) frequency of SNPs associated with I. multifiliis resistance, were hatched from eyed eggs at the disease free recirculated Bornholm Salmon Hatchery, Nexø, Denmark and subsequently reared to the fingerling stage. For this purpose, the first group (QTL-fish) was produced by using sperm from three male genotyped parents carrying SNPs AX-89947214 (Omy17) and AX-89960822 (Omy16), and the other group (non-QTL fish) was produced by using sperm from three other male parents negative for these SNPs. In both cases, sperm was used to fertilize a common pool of eggs stripped from a total of 30 outbred females. Processes of hatching and subsequent rearing of fry to the fingerling stage did not differ between groups of QTL fish and non-QTL fish. From each group (QTL and non-QTL fish) we randomly gathered 100 rainbow trout and transported them (3 h duration) from the hatchery to the infection facility at the University of Copenhagen. Fish were then accommodated and acclimatized 14 d in identical aerated glass tanks with internal biofilters (25 fish per 60 L water, total tank volume 80 L), which were placed in a temperature temperature-controlled room (water temperature constant at 12°C, pH 7.6). We used 30% water change per day to maintain ammonia levels below 0.25. Fish were fed by pelleted feed (1% of fish biomass per day). All fish were genotyped with respect to the two relevant QTLs, one on chomosome 16 and one on chromosome 17. Fish being double heterozugous were excluded from qPCR analysis.

Project description:In this project, effects of chronic temperature changes on the transcriptome of the rainbow trout heart (Oncorhynchus mykiss) were examined. Ectothermic animals of north-temperate latitudes experience large seasonal changes in temperature which strongly affect the rate of body functions. To compensate for the effects of temperature changes ectotherms can respond to chronic temperature changes by increasing the quantity of tissue or enzyme needed for different physiological tasks, or by expressing proteins isoforms which are more appropriate for the new thermal conditions. On the other hand, proteins which are needed in lesser amounts in the new thermal regime could be depressed or down-regulated. Although expression of proteins can be changed by multiple mechanisms during synthesis and degradation, temperature dependent changes in transcription of genes is probably the most important factor in modifying the proteome of the tissues. Rainbow trout are active throughout their thermal tolerance range (0-25°C). Maintenance of adequate cardiac function at different thermal conditions requires a thorough change of the cardiac phenotype which appears as compensatory changes in relative heart mass, energy metabolism, nervous and humoral control of cardiac contractility and in electrical and mechanical properties of the trout heart. Such an extensive structural and functional remodeling of the heart probably necessitates both qualitative and quantitative changes among the numerous macromolecules which constitute the cardiac phenotype and cannot, therefore, be solely based on posttranslational modification of proteins but is expected to require differential gene expression. As a power supply of the circulatory system, the heart is in the focal point of physiological plasticity and sets limits for the activity level of the animal in different thermal conditions. Although several aspects of heart function have been studied in thermally acclimated fish and a number of structural changes have been noticed on exposure to different temperatures, the cellular and molecular mechanisms involved in chronic thermal stress of the fish heart are only partially elucidated. An interesting and poorly examined feature of the cold-acclimated phenotype of the trout heart is the increased heart mass which attenuates the depressive effect of low temperature on cardiac pump function. The heart is a complex organ composed of multiple tissues which together provide the system all necessary qualifications for cardiac pump function. In addition to the contractile and metabolic machinery of the cardiac myocytes, the amount and quality of the extracellular matrix also contribute to the properties of the heart as a muscular pump. Due to the complexity of the heart an enormous amounts of research efforts are needed to find out and examine all crucial aspects of cardiac plasticity required for thermal acclimation. In this regard the screening of gene expression by cDNA micro arrays might provide a broader view to genomic basis of cardiac remodeling under changing temperatures and aid to reveal the candidate genes which are important for thermal acclimation and which might remain unnoticed by traditional biochemical and physiological methods. In the present study we the steady-state effects of temperature acclimation on gene expression of the rainbow trout heart were screened by micro array analysis. Keywords: parallel sample

Project description:In this project, effects of chronic temperature changes on the transcriptome of the rainbow trout heart (Oncorhynchus mykiss) were examined. Ectothermic animals of north-temperate latitudes experience large seasonal changes in temperature which strongly affect the rate of body functions. To compensate for the effects of temperature changes ectotherms can respond to chronic temperature changes by increasing the quantity of tissue or enzyme needed for different physiological tasks, or by expressing proteins isoforms which are more appropriate for the new thermal conditions. On the other hand, proteins which are needed in lesser amounts in the new thermal regime could be depressed or down-regulated. Although expression of proteins can be changed by multiple mechanisms during synthesis and degradation, temperature dependent changes in transcription of genes is probably the most important factor in modifying the proteome of the tissues. Rainbow trout are active throughout their thermal tolerance range (0-25Â°C). Maintenance of adequate cardiac function at different thermal conditions requires a thorough change of the cardiac phenotype which appears as compensatory changes in relative heart mass, energy metabolism, nervous and humoral control of cardiac contractility and in electrical and mechanical properties of the trout heart. Such an extensive structural and functional remodeling of the heart probably necessitates both qualitative and quantitative changes among the numerous macromolecules which constitute the cardiac phenotype and cannot, therefore, be solely based on posttranslational modification of proteins but is expected to require differential gene expression. As a power supply of the circulatory system, the heart is in the focal point of physiological plasticity and sets limits for the activity level of the animal in different thermal conditions. Although several aspects of heart function have been studied in thermally acclimated fish and a number of structural changes have been noticed on exposure to different temperatures, the cellular and molecular mechanisms involved in chronic thermal stress of the fish heart are only partially elucidated. An interesting and poorly examined feature of the cold-acclimated phenotype of the trout heart is the increased heart mass which attenuates the depressive effect of low temperature on cardiac pump function. The heart is a complex organ composed of multiple tissues which together provide the system all necessary qualifications for cardiac pump function. In addition to the contractile and metabolic machinery of the cardiac myocytes, the amount and quality of the extracellular matrix also contribute to the properties of the heart as a muscular pump. Due to the complexity of the heart an enormous amounts of research efforts are needed to find out and examine all crucial aspects of cardiac plasticity required for thermal acclimation. In this regard the screening of gene expression by cDNA micro arrays might provide a broader view to genomic basis of cardiac remodeling under changing temperatures and aid to reveal the candidate genes which are important for thermal acclimation and which might remain unnoticed by traditional biochemical and physiological methods. In the present study we the steady-state effects of temperature acclimation on gene expression of the rainbow trout heart were screened by micro array analysis.

Project description:We used microarrays to investigate the transcriptome of 6 days old male flies exposed to either 15 or 25 C development at either constant or fluctuating temperatures. Further, we investigated gene expression at benign (20C) and high (35C) temperatures With global climate change temperature means and variability are expected to increase. Thus, exposures to elevated temperatures are expected to become an increasing challenge for terrestrial ectotherm populations. While evolutionary adaptation seems to be constrained or proceed at an insufficient pace, many populations are expected to rely on phenotypic plasticity (thermal acclimation) for coping with the predicted changes. However, the effects of fluctuating temperature on the molecular mechanisms and the implications for heat tolerance are not well understood. To understand and predict consequences of climate change it is important to investigate how different components of the thermal environment, including fluctuating thermal conditions, contribute to changes in thermal acclimation. In this study we investigated the impact of mean and diurnal fluctuation of temperature on heat tolerance in Drosophila melanogaster and on the underlying molecular mechanisms in adult male flies. Flies from two constant and two ecologically relevant fluctuating temperature regimes were tested for their critical thermal maxima (CTmax) and associated global gene expression profiles at benign and thermally stressful conditions. Both temperature parameters contributed independently to the thermal acclimation, with regard to heat tolerance as well as the global gene expression profile. Although the independent transcriptional effects caused by fluctuations were relatively small, they are likely to be essential for our understanding of thermal adaptation. Thus, high temperature acclimation ability might not be measured correctly and might even be underestimated at constant temperatures. Our data suggests that the particular mechanisms affected by thermal fluctuations are related to phototransduction and environmental sensing. Thus genes and pathways involved in those processes are likely to be of major importance in a future warmer and more fluctuating climate.

Project description:We used microarrays to investigate the transcriptome of 6 days old male flies exposed to either 15 or 25 C development at either constant or fluctuating temperatures. Further, we investigated gene expression at benign (20C) and high (35C) temperatures With global climate change temperature means and variability are expected to increase. Thus, exposures to elevated temperatures are expected to become an increasing challenge for terrestrial ectotherm populations. While evolutionary adaptation seems to be constrained or proceed at an insufficient pace, many populations are expected to rely on phenotypic plasticity (thermal acclimation) for coping with the predicted changes. However, the effects of fluctuating temperature on the molecular mechanisms and the implications for heat tolerance are not well understood. To understand and predict consequences of climate change it is important to investigate how different components of the thermal environment, including fluctuating thermal conditions, contribute to changes in thermal acclimation. In this study we investigated the impact of mean and diurnal fluctuation of temperature on heat tolerance in Drosophila melanogaster and on the underlying molecular mechanisms in adult male flies. Flies from two constant and two ecologically relevant fluctuating temperature regimes were tested for their critical thermal maxima (CTmax) and associated global gene expression profiles at benign and thermally stressful conditions. Both temperature parameters contributed independently to the thermal acclimation, with regard to heat tolerance as well as the global gene expression profile. Although the independent transcriptional effects caused by fluctuations were relatively small, they are likely to be essential for our understanding of thermal adaptation. Thus, high temperature acclimation ability might not be measured correctly and might even be underestimated at constant temperatures. Our data suggests that the particular mechanisms affected by thermal fluctuations are related to phototransduction and environmental sensing. Thus genes and pathways involved in those processes are likely to be of major importance in a future warmer and more fluctuating climate. Eight experimental groups were analyzed in triplicate, in total 24 Affymetrix GeneChip Drosophila Genome 2.0 Arrays

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