Gene expression associated with white syndromes in a reef building coral, Acropora hyacinthus

Abstract

Background: Corals are capable of launching diverse immune defenses at the site of direct contact with pathogens, but the molecular mechanisms of this activity and the colony-wide effects of such stressors remain poorly understood. Here we compared gene expression profiles in eight healthy Acropora hyacinthus colonies against eight colonies exhibiting tissue loss commonly associated with white syndromes, all collected from a natural reef environment near Palau. Two types of tissues were sampled from diseased corals: visibly affected and apparently healthy. Results: Tag-based RNA-Seq followed by weighted gene co-expression network analysis identified groups of co-regulated differentially expressed genes between all health states (disease lesion, apparently healthy tissues of diseased colonies, and fully healthy). Differences between healthy and diseased tissues indicate activation of several innate immunity and tissue repair pathways accompanied by reduced calcification and the switch towards metabolic reliance on stored lipids. Unaffected parts of diseased colonies, although displaying a trend towards these changes, were not significantly different from fully healthy samples. Still, network analysis identified a group of genes, suggestive of altered immunity state, that were specifically up-regulated in unaffected parts of diseased colonies. Conclusions: Similarity of fully healthy samples to apparently healthy parts of diseased colonies indicates that systemic effects of white syndromes on A. hyacinthus are weak, which implies that the coral colony is largely able to sustain its physiological performance despite disease. The genes specifically up-regulated in unaffected parts of diseased colonies, instead of being the consequence of disease, might be related to the originally higher susceptibility of these colonies to naturally occurring white syndromes.

Metatranscriptome analysis of the reef-building coral Orbicella faveolata indicates holobiont response to coral disease

“…We found that about 1.5% of coral host genes showed differential expression in the diseased state, which is within range of recent coral RNASeq studies (0.05-4%) investigating heat or microbial stress (Barshis et al, 2013;Burge et al, 2013;Libro et al, 2013;Wright et al, 2015). Differentially expressed genes encoded for innate immunity, oxidative stress, translation, and regulation of retroelement activity indicating that the coral host is responding to the WPD infection.…”

“…Differentially expressed genes encoded for innate immunity, oxidative stress, translation, and regulation of retroelement activity indicating that the coral host is responding to the WPD infection. A recent study by Wright et al (2015) also found differential expression of genes related to oxidative stress and translation in diseased tissues. In comparison, transcriptomic adjustment in Symbiodinium was marginal, i.e., only few genes were regulated but with pronounced fold-changes, which aligns with previous stress studies (Leggat et al, 2011;Baumgarten et al, 2013;Libro et al, 2013;Barshis et al, 2014).…”

“…To substantiate the findings discussed in the following, future studies should employ highly replicated designs of the here-developed pipeline to further resolve compartment-and taxa-specific responses. In addition, the analysis of healthy tissue samples from diseased coral colonies (Closek et al, 2014;Wright et al, 2015) promises to yield further insight in regard to separating causes and consequences of coral disease.…”

Host and Symbionts in Pocillopora damicornis Larvae Display Different Transcriptomic Responses to Ocean Acidification and Warming

“…A rank-based gene ontology (GO) analysis was performed to identify GO terms that were significantly enriched by up or down-regulated genes following the method of Wright et al (2015). First, coral and symbiont transcriptomes were translated into protein sequences in TransDecoder v3.0.1 (http://transdecoder.github.io/) using default parameters, and GO terms for the protein sequences were retrieved using InterProScan v5.22-61.0 (Jones et al, 2014).…”

Phenotypic and transcriptomic responses to salinity stress across genetically and geographically divergent Tigriopus californicus populations

“…We performed a rank-based gene ontology (GO) analysis to identify GO categories that were significantly enriched by orthogroups upor down-regulated under low and high salinity stress following the method of Wright, Aglyamova, Meyer, and Matz (2015). First, we retrieved GO terms for the translated northern and southern transcriptomes using INTERPROSCAN version 5.22-61.0 (Jones et al, 2014).…”