Rachel M Wright, Galina V Aglyamova, Eli Meyer, Mikhail V Matz
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 white syndrome-like symptoms, all collected from a natural reef environment near Palau. Two types of tissues were sampled from diseased corals: visibly affected and apparently healthy tissues. Results Tag-based RNA-Seq followed by weighted gene co-expression network analysis identified groups of co-regulated differentially expressed genes between all disease states (diseased, ahead of the lesion, and healthy). Most of the differentially expressed genes were found between tissues at the lesions and asymptomatic (healthy and ahead of the lesion) tissues. These genes were related to innate immunity, oxidative stress responses, lipid metabolism, and calcification. Network analysis also revealed groups of genes regulated specifically in the tissues from diseased colonies that were not yet showing obvious symptoms of disease, indicating a systemic response to infection. Conclusions These observations suggest that tissues ahead of the lesion of disease progression exist in a transitional state between health and lesion appearance. Alternatively, these gene expression profiles capture physiological differences between colonies with varying disease susceptibilities.