Investigating the role of extracellular superoxide in coral health through sensor development and comparative genomics

Abstract:

Reactive oxygen species (ROS), including superoxide, are produced by all aerobic organisms. In marine organisms, intracellular ROS have been implicated in stress and death, while extracellular ROS has myriad beneficial roles. Within corals, ROS, including superoxide, have been implicated in coral bleaching and death. Yet, the concentrations, controls, and enzymatic pathways for extracellular superoxide production in corals are poorly constrained. Using our newly developed diver-operated submersible chemiluminescent sensor (DISCO), we measured in-situ extracellular superoxide associated with healthy corals (Cuba). Extracellular superoxide concentrations varied with coral species; Porites species were consistently associated with the highest superoxide, which was orders of magnitude higher than surrounding seawater. Aquarium-hosted Porites astreoides swimming larvae and settled polyps also produced extracellular superoxide at levels consistent with adults. Bioinformatic analysis of coral protein sequences revealed that all coral species investigated contained various forms of NADPH oxidase (NOX), a group of enzymes that are responsible for extracellular superoxide production in other eukaryotes. Moving forward, by coupling novel sensor based in-situ superoxide measurements with techniques to track superoxide-producing protein expression, we aim to interrogate the link between ROS and coral health, which is vital to predict and prevent future coral reefs loss and coastal ecosystem degradation during changing climates.