Gene expression analysis of resistant (R) and susceptible (S) corals exposed to allogeneic tissue and active White Band Disease (WBD).

<p>Clustered heatmap for gene expression of the 35 annotated differentially expressed genes that differ between resistant (R) and susceptible (S) corals exposed to WBD grafts (D), healthy grafts (H) and unexposed (no graft) controls (C). Hierarchical clustering was performed using Pearson correlation metrics and indicates similarity between the different samples (columns), with <b>resistant and susceptible samples forming different clusters.</b> Red corresponds to up-regulated genes, blue indicates down-regulation. The expression level for each transcript was calculated as log2 fold change of normalized count data. Asterisks indicate transcripts that were DE in both factors (resistance + exposure). See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0146636#pone.0146636.s001" target="_blank">S1 Table</a>.</p

Genetic Signature of Resistance to White Band Disease in the Caribbean Staghorn Coral <i>Acropora cervicornis</i>

<div><p>Coral reefs are declining worldwide due to multiple factors including rising sea surface temperature, ocean acidification, and disease outbreaks. Over the last 30 years, White Band Disease (WBD) alone has killed up to 95% of the Caribbean`s dominant shallow-water corals—the staghorn coral <i>Acropora cervicornis</i> and the elkhorn coral <i>A</i>. <i>palmata</i>. Both corals are now listed on the US Endangered Species Act, and while their recovery has been slow, recent transmission surveys indicate that more than 5% of staghorn corals are disease resistant. Here we compared transcriptome-wide gene expression between resistant and susceptible staghorn corals exposed to WBD using <i>in situ</i> transmission assays. We identified constitutive gene expression differences underlying disease resistance that are independent from the immune response associated with disease exposure. Genes involved in RNA interference-mediated gene silencing, including Argonaute were up-regulated in resistant corals, whereas heat shock proteins (HSPs) were down-regulated. Up-regulation of Argonaute proteins indicates that post-transcriptional gene silencing plays a key, but previously unsuspected role in coral immunity and disease resistance. Constitutive expression of HSPs has been linked to thermal resilience in other <i>Acropora</i> corals, suggesting that the down-regulation of HSPs in disease resistant staghorn corals may confer a dual benefit of thermal resilience.</p></div

Differential expression analyses of RNA-seq data for staghorn coral resistance phenotypes and exposure treatments.

<p>Number of coral transcripts exhibiting significant differential expression (adj p-val<0.05) due to the resistance phenotype (resistant vs susceptible) and to exposure (allogeneic graft vs control; disease graft vs control). Only five transcripts were significant in both treatments (R+E, see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0146636#pone.0146636.s001" target="_blank">S1 Table</a>). No significant interaction was found between resistance and exposure (R*E = 0).</p

Volcano plots displaying differential gene expression between healthy and disease <i>A. cervicornis</i>.

<p>Figure a. plots gene expression values of the putative coral transcripts, figure b. plots putative non coral transcripts. Each point represents an individual gene transcript. Red points represent significantly differentially expressed transcripts (adj p-value < 0.05). </p

Heatmap of immune-related differentially expressed coral transcripts.

<p>Heatmap showing expression profiles of healthy (H) and WBD infected (D) <i>A.cervicornis</i>. Transcripts annotations are based on GO terms and manually curated categories. Relative expression levels are shown in red (up) and blue (down).</p

White Band Disease on <i>Acropora cervicornis</i>.

<p>A colony of the Staghorn coral <i>A. cervicornis</i> infected with White Band Disease showing the characteristic white band of dying and necrotic coral tissue.</p