Dataset Information


Early Transcriptomic response of coral larvae to hyperthermal stress

ABSTRACT: In this study, we examined the very early transcriptional response of aposymbiotic coral larval host (still not engaged in symbiosis) to hyperthermal stress. This experimental setting provided a scenario and opportunity to study the direct effect of environmental stressors on the host cell per se. Using a cDNA microarray constructed for Acropora millepora and Q-RT-PCR assays, we identified a number of genes that were significantly up- and down-regulated with increase of seawater temperature. Down-regulation of several key component of DNA/RNA metabolism was detected implying inhibition of this cellular metabolic process, however the down-regulation of overall protein synthesis was not simple and random, which suggest that the response to stress is a more complicated adjustment to the metabolic needs of the cell. We identified four significant outcomes during the very early hours of the transcriptional response to hyperthermal stress in coral larvae. First, molecular chaperones responded to hyperthermal stress by increasing their expression as expected, but the response was immediate and extremely rapid during the first 3 hours of heat exposure. Secondly, elevated temperature triggers down-regulation of a fluorescent protein homolog, DsRed-type FP, suggesting that this gene might be used as a potential molecular marker for monitoring hyperthermal stress in nature. Thirdly, the downregulation of a coral mannose-binding lectin under hyperthermal stress might compromise the coral immune defense and bring about susceptibility to pathogenic diseases. And lastly, an absence in the response of oxidative stress genes in aposymbiotic coral larvae during the early hours to hyperthermal stress suggest that the up-regulation of cnidarian host oxidative stress genes reported during thermal stress in algal/host symbiosis might be triggered directly by ROS generated by photosynthetic-dysfunctionally algal endosymbionts that diffuse into host cells, as very little ROS seems to be produced by the host cells from thermal-associated host cellular damage. We applied a reference microarray design for the multi-factorial experiment outlined in the study, including two factors: Temperature (3 levels: 24 ˚C, 28 ˚C, 31 ˚C) and Time (2 levels: 3h and 10h). Samples from time zero were used to generate the reference sample for the microarray hybridization experiments. A total of 18 microarrays were used in the entire experiment. Reference samples in each array was labeled with Cy3, and the actual experimenatl samples with Cy5. Ratio-Intensity plots were constructed for each array data to explore whether or not intensity dependence of log ratios, which appears as curvature, was present. Because curvatures were detected in a few of the arrays, an rLowess curve fitting transformation was applied to the data. The transformation was applied to all the arrays to keep consistence in the whole data. Quantile normalisation was also applied to mean log-intensities in order to make the distributions essentially the same across arrays. To detect differentially expressed genes among treatment through the course time of the experiment, a 2-way ANOVA model was fitted to the log transformed intensity data using the microarray analysis software GeneSpring (Agilent Technology). To correct for Type I error derived from multiple testing, the Benjamini and Hochberg method was applied as a false discovery rate (FDR) approach.

ORGANISM(S): Acropora millepora  

SUBMITTER: Ove Hoegh-Guldberg   Saki Harii  Mauricio Rodriguez-Lanetty 

PROVIDER: E-GEOD-16351 | ArrayExpress | 2010-10-08



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