Abstract
BackgroundEcosystems worldwide are suffering the consequences of anthropogenic impact. The diverse ecosystem of coral reefs, for example, are globally threatened by increases in sea surface temperatures due to global warming. Studies to date have focused on determining genetic diversity, the sequence variability of genes in a species, as a proxy to estimate and predict the potential adaptive response of coral populations to environmental changes linked to climate changes. However, the examination of natural gene expression variation has received less attention. This variation has been implicated as an important factor in evolutionary processes, upon which natural selection can act.ResultsWe acclimatized coral nubbins from six colonies of the reef-building coral Acropora millepora to a common garden in Heron Island (Great Barrier Reef, GBR) for a period of four weeks to remove any site-specific environmental effects on the physiology of the coral nubbins. By using a cDNA microarray platform, we detected a high level of gene expression variation, with 17% (488) of the unigenes differentially expressed across coral nubbins of the six colonies (jsFDR-corrected, p < 0.01). Among the main categories of biological processes found differentially expressed were transport, translation, response to stimulus, oxidation-reduction processes, and apoptosis. We found that the transcriptional profiles did not correspond to the genotype of the colony characterized using either an intron of the carbonic anhydrase gene or microsatellite loci markers.ConclusionOur results provide evidence of the high inter-colony variation in A. millepora at the transcriptomic level grown under a common garden and without a correspondence with genotypic identity. This finding brings to our attention the importance of taking into account natural variation between reef corals when assessing experimental gene expression differences. The high transcriptional variation detected in this study is interpreted and discussed within the context of adaptive potential and phenotypic plasticity of reef corals. Whether this variation will allow coral reefs to survive to current challenges remains unknown.
Highlights
Ecosystems worldwide are suffering the consequences of anthropogenic impact
Genotypic identity in A. millepora as detected by a carbonic anhydrase-intron and microsatellite loci markers We detected genotypic differences among 25 colonies tagged of Acropora millepora from the same reef flat on Heron Island (GBR) using the carbonic anhydrase 4–500 intron
The colonies selected for transcriptional profile comparison were genotyped using four microsatellite loci developed for A. millepora by van Oppen et al [43] to further assess genotypic identity in the transplanted coral nubbins from the six colonies of A. millepora in the common garden
Summary
The diverse ecosystem of coral reefs, for example, are globally threatened by increases in sea surface temperatures due to global warming. Molecular, physiological, ecological, and evolutionary levels are imperative if we are to better understand whether coral reefs will survive the unprecedented increasing rates of CO2 and average seawater temperatures, as well as to provide solutions to management programs [10]. It is expected, that the persistence of coral reefs will depend upon the ability of reef corals to respond to these environmental stressors That the persistence of coral reefs will depend upon the ability of reef corals to respond to these environmental stressors (e.g. [11])
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