Associations between transcriptional changes and protein phenotypes provide insights into immune regulation in corals

• Seventeen immune transcripts were differentially expressed post-immune challenge.
• Some positive immune regulators were downregulated post-LPS exposure.
• Putative immune genes were positively correlated to immune protein activity.
• The high disease susceptibility of this species may be a result of “dysfunctional” regulation of some immune genes.

Disease outbreaks in marine ecosystems have driven worldwide declines of numerous taxa, including corals. Some corals, such as Orbicella faveolata, are particularly susceptible to disease. To explore the mechanisms contributing to susceptibility, colonies of O. faveolata were exposed to immune challenge with lipopolysaccharides. RNA sequencing and protein activity assays were used to characterize the response of corals to immune challenge. Differential expression analyses identified 17 immune-related transcripts that varied in expression post-immune challenge. Network analyses revealed several groups of transcripts correlated to immune protein activity. Several transcripts, which were annotated as positive regulators of immunity were included in these groups, and some were downregulated following immune challenge. Correlations between expression of these transcripts and protein activity results further supported the role of these transcripts in positive regulation of immunity. The observed pattern of gene expression and protein activity may elucidate the processes contributing to the disease susceptibility of species like O. faveolata.

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