Dimethylsulfoniopropionate, superoxide dismutase and glutathione as stress response indicators in three corals under short-term hyposalinity stress

Abstract

Corals are among the most active producers of dimethylsulfoniopropionate (DMSP), a key molecule in marine sulfur cycling, yet the specific physiological role of DMSP in corals remains elusive. Here, we examine the oxidative stress response of three coral species (Acropora millepora, Stylophora pistillata and Pocillopora damicornis) and explore the antioxidant role of DMSP and its breakdown products under short-term hyposalinity stress. Symbiont photosynthetic activity declined with hyposalinity exposure in all three reef-building corals. This corresponded with the upregulation of superoxide dismutase and glutathione in the animal host of all three species. For the symbiont component, there were differences in antioxidant regulation, demonstrating differential responses to oxidative stress between the Symbiodinium subclades. Of the three coral species investigated, only A. millepora provided any evidence of the role of DMSP in the oxidative stress response. Our study reveals variability in antioxidant regulation in corals and highlights the influence life-history traits, and the subcladal differences can have on coral physiology. Our data expand on the emerging understanding of the role of DMSP in coral stress regulation and emphasizes the importance of exploring both the host and symbiont responses for defining the threshold of the coral holobiont to hyposalinity stress.

Air exposure of coral is a significant source of dimethylsulfide (DMS) to the atmosphere

“…DMSP is produced by both the algal endosymbiont Symbiodinium 45 and coral host6 which, together with the breakdown products DMS and dimethylsulfoxide (DMSO), has many eco-physiological roles in coral reef ecosystems, including infochemistry in organisms from bacteria to fish, and stress protection78910. Coral-associated DMS production stems from complex interactions in the coral ‘holobiont’ – the combination of coral polyp, endosymbiotic algae and associated microbial community.…”

“…Dimethylated sulfur compounds, particularly DMS and DMSO, readily scavenge harmful hydroxyl radicals and other reactive oxygen species12, a process which may be beneficial to corals during periods of environmental stress810. High intracellular concentrations of DMSP in Symbiodinum sp5.…”

“…Both laboratory and field studies demonstrate strong associations between environmental factors driving oxidative stress (e.g. high light, hyposalinity, high p CO 2 ) and elevated DMSP, DMS and DMSO in pelagic microalgae121314, benthic macroalgae15161718, and corals810. Recent evidence also demonstrates that DMSP appears to be upregulated by corals during recovery from a thermally-induced bleaching event19.…”

Reactive oxygen species (ROS) and dimethylated sulphur compounds in coral explants under acute thermal stress

“…As DMSP represents a major fraction of organic sulphur within marine systems and corals are among the largest producers of DMSP (Broadbent and Jones, 2004), it follows that the biochemical processes thought to be involved with coral bleaching and antioxidant quenching need to be explored with respect to DMSP and ROS (Jones and King, 2015). DMSP is an effective antioxidant (Sunda et al, 2002) and it could act as an additional defence mechanism in corals under oxidative stress (Deschaseaux et al, 2014a;Gardner et al, 2016). However, to date, most studies have only linked the antioxidant function of DMSP by inferring ROS through antioxidant activity or concentrations, instead of measuring ROS directly, which requires a single-cell approach.…”

Quantification of dimethyl sulfide (DMS) production in the sea anemone <i>Aiptasia</i> sp. to simulate the sea-to-air flux from coral reefs

“…The principal cause of bleaching is the overproduction of harmful reactive oxygen species (ROS) mostly originating from the photoinhibition of Photosystem II at increased temperature and irradiance (Tchernov et al, 2011), and Symbiodinium can provide clade-specific defences to harmful ROS including enhanced protection against UV radiation (Baker, 2003), higher growth (Little et al, 2004), and increased thermal tolerance (Baker et al, 2004). Since DMSP and DMS readily scavenge ROS (Sunda et al, 2002) and algae are known to use DMS to mitigate ROS-induced metabolic damage under sublethal environmental stresses (Archer et al, 2010;Dani and Loreto, 2017), it is possible that they are part of an antioxidant mechanism that leads to the scavenging of ROS and production of DMSO in symbiotic cnidarians (Gardner et al, 2016;Jones and King, 2015).…”