Molecular ecology

The coral immune response facilitates protection against microbes during tissue regeneration.

PMID 26095670


Increasing physical damage on coral reefs from predation, storms and anthropogenic disturbances highlights the need to understand the impact of injury on the coral immune system. In this study, we examined the regulation of the coral immune response over 10xa0days following physical trauma artificially inflicted on inxa0situ colonies of the coral Acropora aspera, simultaneously with bacterial colonization of the lesions. Corals responded to injury by increasing the expression of immune system-related genes involved in the Toll-like and NOD-like receptor signalling pathways and the lectin-complement system in three phases (<2, 4 and 10xa0days post-injury). Phenoloxidase activity was also significantly upregulated in two phases (<3 and 10xa0days post-injury), as were levels of non-fluorescent chromoprotein. In addition, green fluorescent protein expression was upregulated in response to injury from 4xa0days post-injury, while cyan fluorescent protein expression was reduced. No shifts in the composition of coral-associated bacterial communities were evident following injury based on 16S rRNA gene amplicon pyrosequencing. Bacteria-specific fluorescence inxa0situ hybridization also showed no evidence of bacterial colonization of the wound or regenerating tissues. Coral tissues showed near-complete regeneration of lesions within 10xa0days. This study demonstrates that corals exhibit immune responses that support rapid recovery following physical injury, maintain coral microbial homeostasis and prevent bacterial infestation that may compromise coral fitness.