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Effects of temperature on gene expression in embryos of the coral Montastraea faveolata.

Voolstra CR, Schnetzer J, Peshkin L, Randall CJ, Szmant AM, Medina M - BMC Genomics (2009)

Bottom Line: Coral reefs are expected to be severely impacted by rising seawater temperatures associated with climate change.This study used cDNA microarrays to investigate transcriptional effects of thermal stress in embryos of the coral Montastraea faveolata.These genes might serve as a basis for research into coral-specific adaptations to stress responses and global climate change.

View Article: PubMed Central - HTML - PubMed

Affiliation: 1Red Sea Research Center, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia. christian.voolstra@kaust.edu.sa

ABSTRACT

Background: Coral reefs are expected to be severely impacted by rising seawater temperatures associated with climate change. This study used cDNA microarrays to investigate transcriptional effects of thermal stress in embryos of the coral Montastraea faveolata. Embryos were exposed to 27.5 degrees C, 29.0 degrees C, and 31.5 degrees C directly after fertilization. Differences in gene expression were measured after 12 and 48 hours.

Results: Analysis of differentially expressed genes indicated that increased temperatures may lead to oxidative stress, apoptosis, and a structural reconfiguration of the cytoskeletal network. Metabolic processes were downregulated, and the action of histones and zinc finger-containing proteins may have played a role in the long-term regulation upon heat stress.

Conclusions: Embryos responded differently depending on exposure time and temperature level. Embryos showed expression of stress-related genes already at a temperature of 29.0 degrees C, but seemed to be able to counteract the initial response over time. By contrast, embryos at 31.5 degrees C displayed continuous expression of stress genes. The genes that played a role in the response to elevated temperatures consisted of both highly conserved and coral-specific genes. These genes might serve as a basis for research into coral-specific adaptations to stress responses and global climate change.

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Model of heat stress response in coral embryos. Upon heat treatment, coral embryos respond with regulation of genes playing a role in system perturbation, system maintenance, and system regulation. These functional groups are interconnected.
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Figure 2: Model of heat stress response in coral embryos. Upon heat treatment, coral embryos respond with regulation of genes playing a role in system perturbation, system maintenance, and system regulation. These functional groups are interconnected.

Mentions: Based on our analysis and assignment of annotated differentially expressed genes, we devised a model of heat stress in coral embryos (Figure 2). Upon temperature increase, cells respond with regulation of genes playing a role in system perturbation, system maintenance, and system regulation. Heat stress induces differential expression of stress-responsive genes. This in turn results in differential expression of genes involved in the response to oxidative stress as heat stress stimulates the production of ROS [37,38]. High levels of oxidative stress in turn have been linked to programmed cell death pathways and cytoskeletal changes [39]. Furthermore, heat stress causes a general downregulation of metabolic processes in coral embryos. As a consequence, ribosome biosynthesis, metabolism, and oxidative phosphorylation are downregulated. These processes are all interconnected. Additionally, heat stress causes misfolding of proteins, which in turn affects the regulation of the protein degradation machinery. On an upstream level, Histone proteins regulate downstream gene expression, and zinc finger proteins might modify those in turn. Please note that this model is based on incomplete transcriptomic data and manual assortment of differentially expressed genes, and therefore subject to change. Furthermore, due to logistical constraints, we were not able to include true biological replicates. Ideally, three to five independent replicated cultures should have been analyzed per treatment and time point to evaluate the potentially contribution of so-called "jar effects" (i.e. the differences between supposedly identical cultures) into the observed gene expression variation. Although jar effects represent a problem for our analysis, we hope that most of the observed gene expression patterns represent the true response to the treatments, because 1) our results are in correspondence with results from other heat stress studies in other organisms, 2) we find a stronger stress response in larvae treated at higher temperatures, and 3) a similar study that we conducted with Acropora palmata larvae in which we did assay biological replicates gave similar results (data not shown). We therefore acknowledge that implications drawn from these data are limited and follow-up studies (e.g. qPCR) with proper biological replication are necessary to validate results and conclusions presented here. Future efforts should concentrate on comparing transcriptomic responses to different stressors in coral embryos in order to identify a set of common and specific key response genes. These key genes could then serve as a repository for stressor-specific biomarkers as well as for research into coral-specific adaptations to stress responses and global climate change.


Effects of temperature on gene expression in embryos of the coral Montastraea faveolata.

Voolstra CR, Schnetzer J, Peshkin L, Randall CJ, Szmant AM, Medina M - BMC Genomics (2009)

Model of heat stress response in coral embryos. Upon heat treatment, coral embryos respond with regulation of genes playing a role in system perturbation, system maintenance, and system regulation. These functional groups are interconnected.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2807443&req=5

Figure 2: Model of heat stress response in coral embryos. Upon heat treatment, coral embryos respond with regulation of genes playing a role in system perturbation, system maintenance, and system regulation. These functional groups are interconnected.
Mentions: Based on our analysis and assignment of annotated differentially expressed genes, we devised a model of heat stress in coral embryos (Figure 2). Upon temperature increase, cells respond with regulation of genes playing a role in system perturbation, system maintenance, and system regulation. Heat stress induces differential expression of stress-responsive genes. This in turn results in differential expression of genes involved in the response to oxidative stress as heat stress stimulates the production of ROS [37,38]. High levels of oxidative stress in turn have been linked to programmed cell death pathways and cytoskeletal changes [39]. Furthermore, heat stress causes a general downregulation of metabolic processes in coral embryos. As a consequence, ribosome biosynthesis, metabolism, and oxidative phosphorylation are downregulated. These processes are all interconnected. Additionally, heat stress causes misfolding of proteins, which in turn affects the regulation of the protein degradation machinery. On an upstream level, Histone proteins regulate downstream gene expression, and zinc finger proteins might modify those in turn. Please note that this model is based on incomplete transcriptomic data and manual assortment of differentially expressed genes, and therefore subject to change. Furthermore, due to logistical constraints, we were not able to include true biological replicates. Ideally, three to five independent replicated cultures should have been analyzed per treatment and time point to evaluate the potentially contribution of so-called "jar effects" (i.e. the differences between supposedly identical cultures) into the observed gene expression variation. Although jar effects represent a problem for our analysis, we hope that most of the observed gene expression patterns represent the true response to the treatments, because 1) our results are in correspondence with results from other heat stress studies in other organisms, 2) we find a stronger stress response in larvae treated at higher temperatures, and 3) a similar study that we conducted with Acropora palmata larvae in which we did assay biological replicates gave similar results (data not shown). We therefore acknowledge that implications drawn from these data are limited and follow-up studies (e.g. qPCR) with proper biological replication are necessary to validate results and conclusions presented here. Future efforts should concentrate on comparing transcriptomic responses to different stressors in coral embryos in order to identify a set of common and specific key response genes. These key genes could then serve as a repository for stressor-specific biomarkers as well as for research into coral-specific adaptations to stress responses and global climate change.

Bottom Line: Coral reefs are expected to be severely impacted by rising seawater temperatures associated with climate change.This study used cDNA microarrays to investigate transcriptional effects of thermal stress in embryos of the coral Montastraea faveolata.These genes might serve as a basis for research into coral-specific adaptations to stress responses and global climate change.

View Article: PubMed Central - HTML - PubMed

Affiliation: 1Red Sea Research Center, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia. christian.voolstra@kaust.edu.sa

ABSTRACT

Background: Coral reefs are expected to be severely impacted by rising seawater temperatures associated with climate change. This study used cDNA microarrays to investigate transcriptional effects of thermal stress in embryos of the coral Montastraea faveolata. Embryos were exposed to 27.5 degrees C, 29.0 degrees C, and 31.5 degrees C directly after fertilization. Differences in gene expression were measured after 12 and 48 hours.

Results: Analysis of differentially expressed genes indicated that increased temperatures may lead to oxidative stress, apoptosis, and a structural reconfiguration of the cytoskeletal network. Metabolic processes were downregulated, and the action of histones and zinc finger-containing proteins may have played a role in the long-term regulation upon heat stress.

Conclusions: Embryos responded differently depending on exposure time and temperature level. Embryos showed expression of stress-related genes already at a temperature of 29.0 degrees C, but seemed to be able to counteract the initial response over time. By contrast, embryos at 31.5 degrees C displayed continuous expression of stress genes. The genes that played a role in the response to elevated temperatures consisted of both highly conserved and coral-specific genes. These genes might serve as a basis for research into coral-specific adaptations to stress responses and global climate change.

Show MeSH
Related in: MedlinePlus