Limits...
Host Coenzyme Q Redox State Is an Early Biomarker of Thermal Stress in the Coral Acropora millepora.

Lutz A, Raina JB, Motti CA, Miller DJ, van Oppen MJ - PLoS ONE (2015)

Bottom Line: The current consensus is that this phenomenon results from enhanced production of harmful reactive oxygen species (ROS) that disrupt the symbiosis between corals and their endosymbiotic dinoflagellates, Symbiodinium.The results show that the responses of the two antioxidant systems occur on different timescales: (i) the redox state of the Symbiodinium PQ pool remained stable until twelve days into the experiment, after which there was an abrupt oxidative shift; (ii) by contrast, an oxidative shift of approximately 10% had occurred in the host CoQ pool after 6 days of thermal stress, prior to significant changes in any other physiological parameter measured.Host CoQ pool oxidation is thus an early biomarker of thermal stress in corals, and this antioxidant pool is likely to play a key role in quenching thermally-induced ROS in the coral-algal symbiosis.

View Article: PubMed Central - PubMed

Affiliation: AIMS@JCU, James Cook University, Townsville, Queensland, Australia; Australian Institute of Marine Science, Townsville, Queensland, Australia; Comparative Genomics Centre and Department of Molecular and Cell Biology, James Cook University, Townsville, Queensland, Australia; ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia.

ABSTRACT
Bleaching episodes caused by increasing seawater temperatures may induce mass coral mortality and are regarded as one of the biggest threats to coral reef ecosystems worldwide. The current consensus is that this phenomenon results from enhanced production of harmful reactive oxygen species (ROS) that disrupt the symbiosis between corals and their endosymbiotic dinoflagellates, Symbiodinium. Here, the responses of two important antioxidant defence components, the host coenzyme Q (CoQ) and symbiont plastoquinone (PQ) pools, are investigated for the first time in colonies of the scleractinian coral, Acropora millepora, during experimentally-induced bleaching under ecologically relevant conditions. Liquid chromatography-mass spectrometry (LC-MS) was used to quantify the states of these two pools, together with physiological parameters assessing the general state of the symbiosis (including photosystem II photochemical efficiency, chlorophyll concentration and Symbiodinium cell densities). The results show that the responses of the two antioxidant systems occur on different timescales: (i) the redox state of the Symbiodinium PQ pool remained stable until twelve days into the experiment, after which there was an abrupt oxidative shift; (ii) by contrast, an oxidative shift of approximately 10% had occurred in the host CoQ pool after 6 days of thermal stress, prior to significant changes in any other physiological parameter measured. Host CoQ pool oxidation is thus an early biomarker of thermal stress in corals, and this antioxidant pool is likely to play a key role in quenching thermally-induced ROS in the coral-algal symbiosis. This study adds to a growing body of work that indicates host cellular responses may precede the bleaching process and symbiont dysfunction.

No MeSH data available.


Related in: MedlinePlus

Temperature logger data for the experimental period.Thermal log of the four temperature sensors placed in heated (32°C) and control (27°C) seawater aquarium tanks for the duration of the experimental period. Two temperature sensors were used per treatment. Dashed lines indicate sampling time points.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4591267&req=5

pone.0139290.g001: Temperature logger data for the experimental period.Thermal log of the four temperature sensors placed in heated (32°C) and control (27°C) seawater aquarium tanks for the duration of the experimental period. Two temperature sensors were used per treatment. Dashed lines indicate sampling time points.

Mentions: The colony fragments were acclimated for two weeks prior to starting the experiment, then seawater temperatures in four tanks were ramped at a constant rate (0.7°C d-1) to 32 ± 0.5°C over seven days; the remaining four control tanks were maintained at 27°C for the entire duration of the experiment (Fig 1). The heat stress temperature was chosen to represent an ecologically relevant 1°C above the estimated local bleaching threshold of approximately 31°C for nearby Orpheus Island, Great Barrier Reef (18°35’ S/146°29’ E; ~31°C: [40]). Coral branches were sampled at four time points during the experiment: at the end of the acclimation period (t = 0 d), upon reaching the 32°C target temperature in the hyperthermal stress treatment (t = 7 d), and after five (t = 12 d) and ten days (t = 17 d) at 32°C. At each time point, coral nubbins (approximately 50 mm in length) were collected from each coral fragment after six hours of light (n = 12 in control and heat treatment, respectively) and from a subset of fragments after six hours of darkness (n = 9 in control and heat treatment, respectively). Samples were immediately snap-frozen in liquid nitrogen at time of collection to quench the PQ and CoQ pool redox states. Total sample size was optimised to ensure all samples could be processed in less than four weeks after sampling to ascertain the redox stability of the extracts.


Host Coenzyme Q Redox State Is an Early Biomarker of Thermal Stress in the Coral Acropora millepora.

Lutz A, Raina JB, Motti CA, Miller DJ, van Oppen MJ - PLoS ONE (2015)

Temperature logger data for the experimental period.Thermal log of the four temperature sensors placed in heated (32°C) and control (27°C) seawater aquarium tanks for the duration of the experimental period. Two temperature sensors were used per treatment. Dashed lines indicate sampling time points.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4591267&req=5

pone.0139290.g001: Temperature logger data for the experimental period.Thermal log of the four temperature sensors placed in heated (32°C) and control (27°C) seawater aquarium tanks for the duration of the experimental period. Two temperature sensors were used per treatment. Dashed lines indicate sampling time points.
Mentions: The colony fragments were acclimated for two weeks prior to starting the experiment, then seawater temperatures in four tanks were ramped at a constant rate (0.7°C d-1) to 32 ± 0.5°C over seven days; the remaining four control tanks were maintained at 27°C for the entire duration of the experiment (Fig 1). The heat stress temperature was chosen to represent an ecologically relevant 1°C above the estimated local bleaching threshold of approximately 31°C for nearby Orpheus Island, Great Barrier Reef (18°35’ S/146°29’ E; ~31°C: [40]). Coral branches were sampled at four time points during the experiment: at the end of the acclimation period (t = 0 d), upon reaching the 32°C target temperature in the hyperthermal stress treatment (t = 7 d), and after five (t = 12 d) and ten days (t = 17 d) at 32°C. At each time point, coral nubbins (approximately 50 mm in length) were collected from each coral fragment after six hours of light (n = 12 in control and heat treatment, respectively) and from a subset of fragments after six hours of darkness (n = 9 in control and heat treatment, respectively). Samples were immediately snap-frozen in liquid nitrogen at time of collection to quench the PQ and CoQ pool redox states. Total sample size was optimised to ensure all samples could be processed in less than four weeks after sampling to ascertain the redox stability of the extracts.

Bottom Line: The current consensus is that this phenomenon results from enhanced production of harmful reactive oxygen species (ROS) that disrupt the symbiosis between corals and their endosymbiotic dinoflagellates, Symbiodinium.The results show that the responses of the two antioxidant systems occur on different timescales: (i) the redox state of the Symbiodinium PQ pool remained stable until twelve days into the experiment, after which there was an abrupt oxidative shift; (ii) by contrast, an oxidative shift of approximately 10% had occurred in the host CoQ pool after 6 days of thermal stress, prior to significant changes in any other physiological parameter measured.Host CoQ pool oxidation is thus an early biomarker of thermal stress in corals, and this antioxidant pool is likely to play a key role in quenching thermally-induced ROS in the coral-algal symbiosis.

View Article: PubMed Central - PubMed

Affiliation: AIMS@JCU, James Cook University, Townsville, Queensland, Australia; Australian Institute of Marine Science, Townsville, Queensland, Australia; Comparative Genomics Centre and Department of Molecular and Cell Biology, James Cook University, Townsville, Queensland, Australia; ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia.

ABSTRACT
Bleaching episodes caused by increasing seawater temperatures may induce mass coral mortality and are regarded as one of the biggest threats to coral reef ecosystems worldwide. The current consensus is that this phenomenon results from enhanced production of harmful reactive oxygen species (ROS) that disrupt the symbiosis between corals and their endosymbiotic dinoflagellates, Symbiodinium. Here, the responses of two important antioxidant defence components, the host coenzyme Q (CoQ) and symbiont plastoquinone (PQ) pools, are investigated for the first time in colonies of the scleractinian coral, Acropora millepora, during experimentally-induced bleaching under ecologically relevant conditions. Liquid chromatography-mass spectrometry (LC-MS) was used to quantify the states of these two pools, together with physiological parameters assessing the general state of the symbiosis (including photosystem II photochemical efficiency, chlorophyll concentration and Symbiodinium cell densities). The results show that the responses of the two antioxidant systems occur on different timescales: (i) the redox state of the Symbiodinium PQ pool remained stable until twelve days into the experiment, after which there was an abrupt oxidative shift; (ii) by contrast, an oxidative shift of approximately 10% had occurred in the host CoQ pool after 6 days of thermal stress, prior to significant changes in any other physiological parameter measured. Host CoQ pool oxidation is thus an early biomarker of thermal stress in corals, and this antioxidant pool is likely to play a key role in quenching thermally-induced ROS in the coral-algal symbiosis. This study adds to a growing body of work that indicates host cellular responses may precede the bleaching process and symbiont dysfunction.

No MeSH data available.


Related in: MedlinePlus