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1
Henderson, Meegan, Tracy Ainsworth, and Ove Hoegh-Guldberg. "Coral microbial ecology under the microscope." Microbiology Australia 28, no. 3 (2007): 111. http://dx.doi.org/10.1071/ma07111.
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Increasing episodes of mass coral bleaching and a growing number of reports of coral disease epizootics have led to an expanding research field investigating the microbial ecology of reef building corals. Corals reside in a complex ecosystem and form intimate symbiotic relationships with eukaryotic dinoflagellates (commonly called zooxanthellae), which have been well studied. Less understood is the complex interactions that corals form with Bacteria, Archaea and viruses, all of which play an important functional role in coral health. Understanding how the coral animal and its symbiotic partners (eukaryotic, bacterial, archeal and viral) are influenced by environmental perturbations such as global climate change, rising sea surface temperatures and increasing anthropogenic inputs into the ecosystem such as nutrients, is the driving factor behind this expanding microbial discipline.
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Rosic, Nedeljka N., and Sophie Dove. "Mycosporine-Like Amino Acids from Coral Dinoflagellates." Applied and Environmental Microbiology 77, no. 24 (October 14, 2011): 8478–86. http://dx.doi.org/10.1128/aem.05870-11.
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ABSTRACTCoral reefs are one of the most important marine ecosystems, providing habitat for approximately a quarter of all marine organisms. Within the foundation of this ecosystem, reef-building corals form mutualistic symbioses with unicellular photosynthetic dinoflagellates of the genusSymbiodinium. Exposure to UV radiation (UVR) (280 to 400 nm) especially when combined with thermal stress has been recognized as an important abiotic factor leading to the loss of algal symbionts from coral tissue and/or a reduction in their pigment concentration and coral bleaching. UVR may damage biological macromolecules, increase the level of mutagenesis in cells, and destabilize the symbiosis between the coral host and their dinoflagellate symbionts. In nature, corals and other marine organisms are protected from harmful UVR through several important photoprotective mechanisms that include the synthesis of UV-absorbing compounds such as mycosporine-like amino acids (MAAs). MAAs are small (<400-Da), colorless, water-soluble compounds made of a cyclohexenone or cyclohexenimine chromophore that is bound to an amino acid residue or its imino alcohol. These secondary metabolites are natural biological sunscreens characterized by a maximum absorbance in the UVA and UVB ranges of 310 to 362 nm. In addition to their photoprotective role, MAAs act as antioxidants scavenging reactive oxygen species (ROS) and suppressing singlet oxygen-induced damage. It has been proposed that MAAs are synthesized during the first part of the shikimate pathway, and recently, it has been suggested that they are synthesized in the pentose phosphate pathway. The shikimate pathway is not found in animals, but in plants and microbes, it connects the metabolism of carbohydrates to the biosynthesis of aromatic compounds. However, both the complete enzymatic pathway of MAA synthesis and the extent of their regulation by environmental conditions are not known. This minireview discusses the current knowledge of MAA synthesis, illustrates the diversity of MAA functions, and opens new perspectives for future applications of MAAs in biotechnology.
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Jones, Ross J., Selina Ward, Affendi Yang Amri, and Ove Hoegh-Guldberg. "Changes in quantum efficiency of Photosystem II of symbiotic dinoflagellates of corals after heat stress, and of bleached corals sampled after the 1998 Great Barrier Reef mass bleaching event." Marine and Freshwater Research 51, no. 1 (2000): 63. http://dx.doi.org/10.1071/mf99100.
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Pulse–amplitude–modulation chlorophyll fluorometry was used to examine changes in dark-adapted Fv/Fm of endosymbiotic dinoflagellate microalgae within the tissues of the temperate coral Plesiastrea versipora exposed to elevated seawater temperature. The Fv/Fm was markedly reduced following exposure of corals to 28°C for 48 h. When corals were returned to ambient (24°C) conditions, Fv/Fm increased in an initial rapid and then secondary slower phase. Tissue discolouration (coral bleaching), caused by a significant decrease in the density of algae, was observed during the first 2–3 days of the recovery period. After 14 days, Fv/Fm was still significantly lower than in control corals. The recovery of Fv/Fm is discussed in terms of repair processes within the symbiotic algae, division of healthy algae and also the selective removal of photo-damaged dinoflagellates. Under field conditions, bleached corals sampled at Heron Island Reef during a bleaching event had significantly lower Fv/Fm than non-bleached colonies; four months after the bleaching event, there were no differences in F v /F m or algal density in corals marked as having bleached or having shown no signs of colour loss. The results of this laboratory and field study are consistent with the hypothesis that an impairment of photosynthesis occurs during heat-stress, and is the underlying cause of coral bleaching.
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Shoguchi, Eiichi, Yuki Yoshioka, Chuya Shinzato, Asuka Arimoto, Debashish Bhattacharya, and Noriyuki Satoh. "Correlation between Organelle Genetic Variation and RNA Editing in Dinoflagellates Associated with the Coral Acropora digitifera." Genome Biology and Evolution 12, no. 3 (February 27, 2020): 203–9. http://dx.doi.org/10.1093/gbe/evaa042.
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Abstract In order to develop successful strategies for coral reef preservation, it is critical that the biology of both host corals and symbiotic algae are investigated. In the Ryukyu Archipelago, which encompasses many islands spread over ∼500 km of the Pacific Ocean, four major populations of the coral Acropora digitifera have been studied using whole-genome shotgun (WGS) sequence analysis (Shinzato C, Mungpakdee S, Arakaki N, Satoh N. 2015. Genome-wide single-nucleotide polymorphism (SNP) analysis explains coral diversity and recovery in the Ryukyu Archipelago. Sci Rep. 5:18211.). In contrast, the diversity of the symbiotic dinoflagellates associated with these A. digitifera populations is unknown. It is therefore unclear if these two core components of the coral holobiont share a common evolutionary history. This issue can be addressed for the symbiotic algal populations by studying the organelle genomes of their mitochondria and plastids. Here, we analyzed WGS data from ∼150 adult A. digitifera, and by mapping reads to the available reference genome sequences, we extracted 2,250 sequences representing 15 organelle genes of Symbiodiniaceae. Molecular phylogenetic analyses of these mitochondrial and plastid gene sets revealed that A. digitifera from the southern Yaeyama islands harbor a different Symbiodiniaceae population than the islands of Okinawa and Kerama in the north, indicating that the distribution of symbiont populations partially matches that of the four host populations. Interestingly, we found that numerous SNPs correspond to known RNA-edited sites in 14 of the Symbiodiniaceae organelle genes, with mitochondrial genes showing a stronger correspondence than plastid genes. These results suggest a possible correlation between RNA editing and SNPs in the two organelle genomes of symbiotic dinoflagellates.
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Lema, Kimberley A., Bette L. Willis, and David G. Bourne. "Corals Form Characteristic Associations with Symbiotic Nitrogen-Fixing Bacteria." Applied and Environmental Microbiology 78, no. 9 (February 17, 2012): 3136–44. http://dx.doi.org/10.1128/aem.07800-11.
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ABSTRACTThe complex symbiotic relationship between corals and their dinoflagellate partnerSymbiodiniumis believed to be sustained through close associations with mutualistic bacterial communities, though little is known about coral associations with bacterial groups able to fix nitrogen (diazotrophs). In this study, we investigated the diversity of diazotrophic bacterial communities associated with three common coral species (Acropora millepora,Acropora muricata, andPocillopora damicormis) from three midshelf locations of the Great Barrier Reef (GBR) by profiling the conserved subunit of thenifHgene, which encodes the dinitrogenase iron protein. Comparisons of diazotrophic community diversity among coral tissue and mucus microenvironments and the surrounding seawater revealed that corals harbor diversenifHphylotypes that differ between tissue and mucus microhabitats. Coral mucusnifHsequences displayed high heterogeneity, and many bacterial groups overlapped with those found in seawater. Moreover, coral mucus diazotrophs were specific neither to coral species nor to reef location, reflecting the ephemeral nature of coral mucus. In contrast, the dominant diazotrophic bacteria in tissue samples differed among coral species, with differences remaining consistent at all three reefs, indicating that coral-diazotroph associations are species specific. Notably, dominant diazotrophs for all coral species were closely related to the bacterial group rhizobia, which represented 71% of the total sequences retrieved from tissue samples. The species specificity of coral-diazotroph associations further supports the coral holobiont model that bacterial groups associated with corals are conserved. Our results suggest that, as in terrestrial plants, rhizobia have developed a mutualistic relationship with corals and may contribute fixed nitrogen toSymbiodinium.
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Wooldridge, S. A. "A hypothesis linking sub-optimal seawater <i>p</i>CO<sub>2</sub> conditions for cnidarian-<i>Symbiodinium</i> symbioses with the exceedence of the interglacial threshold (> 260 ppmv)." Biogeosciences Discussions 8, no. 6 (November 23, 2011): 11215–53. http://dx.doi.org/10.5194/bgd-8-11215-2011.
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Abstract. Most scleractinian corals and many other cnidarians host intracellular photosynthetic dinoflagellate symbionts ("zooxanthellae"). The zooxanthellae contribute to host metabolism and skeletogenesis to such an extent that this symbiosis is well recognised for its contribution in creating the coral reef ecosystem. The stable functioning of cnidarian symbioses is however dependent upon the host's ability to maintain demographic control of its algal partner. In this review, I explain how the modern envelope of seawater conditions found within many coral reef ecosystems (characterised by elevated temperatures, rising pCO2, and enriched nutrient levels) are antagonistic toward the dominant host processes that restrict excessive symbiont proliferation. Moreover, I outline a new hypothesis and initial evidence base, which support the suggestion that the additional "excess" zooxanthellae fraction permitted by seawater pCO2 levels beyond 260 ppmv significantly increases the propensity for symbiosis breakdown ("bleaching") in response to temperature and irradiance extremes. The relevance of this biological threshold is discussed in terms of historical reef extinction events, glacial-interglacial climate cycles and the modern decline of coral reef ecosystems.
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Wooldridge, S. A. "A hypothesis linking sub-optimal seawater <I>p</I>CO<sub>2</sub> conditions for cnidarian-<I>Symbiodinium</I> symbioses with the exceedence of the interglacial threshold (>260 ppmv)." Biogeosciences 9, no. 5 (May 15, 2012): 1709–23. http://dx.doi.org/10.5194/bg-9-1709-2012.
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Abstract. Most scleractinian corals and many other cnidarians host intracellular photosynthetic dinoflagellate symbionts ("zooxanthellae"). The zooxanthellae contribute to host metabolism and skeletogenesis to such an extent that this symbiosis is well recognised for its contribution in creating the coral reef ecosystem. The stable functioning of cnidarian symbioses is however dependent upon the host's ability to maintain demographic control of its algal partner. In this review, I explain how the modern envelope of seawater conditions found within many coral reef ecosystems (characterised by elevated temperatures, rising pCO2, and enriched nutrient levels) are antagonistic toward the dominant host processes that restrict excessive symbiont proliferation. Moreover, I outline a new hypothesis and initial evidence base, which support the suggestion that the additional "excess" zooxanthellae fraction permitted by seawater pCO2 levels beyond 260 ppmv significantly increases the propensity for symbiosis breakdown ("bleaching") in response to temperature and irradiance extremes. The relevance of this biological threshold is discussed in terms of historical reef extinction events, glacial-interglacial climate cycles and the modern decline of coral reef ecosystems.
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Frommlet, Jörg C., Maria L. Sousa, Artur Alves, Sandra I. Vieira, David J. Suggett, and João Serôdio. "Coral symbiotic algae calcifyex hospitein partnership with bacteria." Proceedings of the National Academy of Sciences 112, no. 19 (April 27, 2015): 6158–63. http://dx.doi.org/10.1073/pnas.1420991112.
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Dinoflagellates of the genusSymbiodiniumare commonly recognized as invertebrate endosymbionts that are of central importance for the functioning of coral reef ecosystems. However, the endosymbiotic phase withinSymbiodiniumlife history is inherently tied to a more cryptic free-living (ex hospite) phase that remains largely unexplored. Here we show that free-livingSymbiodiniumspp. in culture commonly form calcifying bacterial–algal communities that produce aragonitic spherulites and encase the dinoflagellates as endolithic cells. This process is driven bySymbiodiniumphotosynthesis but occurs only in partnership with bacteria. Our findings not only place dinoflagellates on the map of microbial–algal organomineralization processes but also point toward an endolithic phase in theSymbiodiniumlife history, a phenomenon that may provide new perspectives on the biology and ecology ofSymbiodiniumspp. and the evolutionary history of the coral–dinoflagellate symbiosis.
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González-Espinosa, PC, and SD Donner. "Predicting cold-water bleaching in corals: role of temperature, and potential integration of light exposure." Marine Ecology Progress Series 642 (May 28, 2020): 133–46. http://dx.doi.org/10.3354/meps13336.
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Warm-water growth and survival of corals are constrained by a set of environmental conditions such as temperature, light, nutrient levels and salinity. Water temperatures of 1 to 2°C above the usual summer maximum can trigger a phenomenon known as coral bleaching, whereby disruption of the symbiosis between coral and dinoflagellate micro-algae, living within the coral tissue, reveals the white skeleton of coral. Anomalously cold water can also lead to coral bleaching but has been the subject of limited research. Although cold-water bleaching events are less common, they can produce similar impacts on coral reefs as warm-water events. In this study, we explored the effect of temperature and light on the likelihood of cold-water coral bleaching from 1998-2017 using available bleaching observations from the Eastern Tropical Pacific and the Florida Keys. Using satellite-derived sea surface temperature, photosynthetically available radiation and light attenuation data, cold temperature and light exposure metrics were developed and then tested against the bleaching observations using logistic regression. The results show that cold-water bleaching can be best predicted with an accumulated cold-temperature metric, i.e. ‘degree cooling weeks’, analogous to the heat stress metric ‘degree heating weeks’, with high accuracy (90%) and fewer Type I and Type II errors in comparison with other models. Although light, when also considered, improved prediction accuracy, we found that the most reliable framework for cold-water bleaching prediction may be based solely on cold-temperature exposure.
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Fujita, K., M. Hikami, A. Suzuki, A. Kuroyanagi, K. Sakai, H. Kawahata, and Y. Nojiri. "Effects of ocean acidification on calcification of symbiont-bearing reef foraminifers." Biogeosciences 8, no. 8 (August 4, 2011): 2089–98. http://dx.doi.org/10.5194/bg-8-2089-2011.
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Abstract. Ocean acidification (decreases in carbonate ion concentration and pH) in response to rising atmospheric pCO2 is generally expected to reduce rates of calcification by reef calcifying organisms, with potentially severe implications for coral reef ecosystems. Large, algal symbiont-bearing benthic foraminifers, which are important primary and carbonate producers in coral reefs, produce high-Mg calcite shells, whose solubility can exceed that of aragonite produced by corals, making them the "first responder" in coral reefs to the decreasing carbonate saturation state of seawater. Here we report results of culture experiments performed to assess the effects of ongoing ocean acidification on the calcification of symbiont-bearing reef foraminifers using a high-precision pCO2 control system. Living clone individuals of three foraminiferal species (Baculogypsina sphaerulata, Calcarina gaudichaudii, and Amphisorus hemprichii) were subjected to seawater at five pCO2 levels from 260 to 970 μatm. Cultured individuals were maintained for about 12 weeks in an indoor flow-through system under constant water temperature, light intensity, and photoperiod. After the experiments, the shell diameter and weight of each cultured specimen were measured. Net calcification of B. sphaerulata and C. gaudichaudii, which secrete a hyaline shell and host diatom symbionts, increased under intermediate levels of pCO2 (580 and/or 770 μatm) and decreased at a higher pCO2 level (970 μatm). Net calcification of A. hemprichii, which secretes a porcelaneous shell and hosts dinoflagellate symbionts, tended to decrease at elevated pCO2. Observed different responses between hyaline and porcelaneous species are possibly caused by the relative importance of elevated pCO2, which induces CO2 fertilization effects by algal symbionts, versus associated changes in seawater carbonate chemistry, which decreases a carbonate concentration. Our findings suggest that ongoing ocean acidification might favor symbiont-bearing reef foraminifers with hyaline shells at intermediate pCO2 levels (580 to 770 μatm) but be unfavorable to those with either hyaline or porcelaneous shells at higher pCO2 levels (near 1000 μatm).
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Fujita, K., M. Hikami, A. Suzuki, A. Kuroyanagi, and H. Kawahata. "Effects of ocean acidification on calcification of symbiont-bearing reef foraminifers." Biogeosciences Discussions 8, no. 1 (February 25, 2011): 1809–29. http://dx.doi.org/10.5194/bgd-8-1809-2011.
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Abstract. Ocean acidification (decreases in carbonate ion concentration and pH) in response to rising atmospheric pCO2 is generally expected to reduce rates of calcification by reef calcifying organisms, with potentially severe implications for coral reef ecosystems. Large, algal symbiont-bearing benthic foraminifers, which are important primary and carbonate producers in coral reefs, produce high-Mg calcite shells, whose solubility can exceed that of aragonite produced by corals, making them the "first responder" in coral reefs to the decreasing carbonate saturation state of seawater. Here we report results of culture experiments performed to assess the effects of ongoing ocean acidification on the calcification of symbiont-bearing reef foraminifers using a high-precision pCO2 control system. Living clone individuals of three foraminiferal species (Baculogypsina sphaerulata, Calcarina gaudichaudii, and Amphisorus hemprichii) were subjected to seawater at five pCO2 levels from 260 to 970 μatm. Cultured individuals were maintained for about 12 weeks in an indoor flow-through system under constant water temperature, light intensity, and photoperiod. After the experiments, the shell diameter and weight of each cultured specimen were measured. Net calcification of Baculogypsina and Calcarina, which secrete a hyaline shell and host diatom symbionts, increased under intermediate levels of pCO2 (580 and/or 770 μatm) and decreased at a higher pCO2 level (970 μatm). Net calcification of Amphisorus, which secretes a porcelaneous shell and hosts dinoflagellate symbionts, tended to decrease at elevated pCO2. These different responses among the three species are possibly due to differences in calcification mechanisms (in particular, the specific carbonate species used for calcification) between hyaline and porcelaneous taxa, and to links between calcification by the foraminiferal hosts and photosynthesis by the algal endosymbionts. Our findings suggest that ongoing ocean acidification might favor symbiont-bearing reef foraminifers with hyaline shells at intermediate pCO2 levels (580 to 770 μatm) but be unfavorable to those with either hyaline or porcelaneous shells at higher pCO2 levels (near 1000 μatm).
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Herrera, Marcela, Shannon G. Klein, Sara Campana, Jit Ern Chen, Arun Prasanna, Carlos M. Duarte, and Manuel Aranda. "Temperature transcends partner specificity in the symbiosis establishment of a cnidarian." ISME Journal 15, no. 1 (September 15, 2020): 141–53. http://dx.doi.org/10.1038/s41396-020-00768-y.
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AbstractCoral reef research has predominantly focused on the effect of temperature on the breakdown of coral-dinoflagellate symbioses. However, less is known about how increasing temperature affects the establishment of new coral-dinoflagellate associations. Inter-partner specificity and environment-dependent colonization are two constraints proposed to limit the acquisition of more heat tolerant symbionts. Here, we investigated the symbiotic dynamics of various photosymbionts in different host genotypes under “optimal” and elevated temperature conditions. To do this, we inoculated symbiont-free polyps of the sea anemone Exaiptasia pallida originating from Hawaii (H2), North Carolina (CC7), and the Red Sea (RS) with the same mixture of native symbiont strains (Breviolum minutum, Symbiodinium linucheae, S. microadriaticum, and a Breviolum type from the Red Sea) at 25 and 32 °C, and assessed their ITS2 composition, colonization rates, and PSII photochemical efficiency (Fv/Fm). Symbiont communities across thermal conditions differed significantly for all hosts, suggesting that temperature rather than partner specificity had a stronger effect on symbiosis establishment. Overall, we detected higher abundances of more heat resistant Symbiodiniaceae types in the 32 °C treatments. Our data further showed that PSII photophysiology under elevated temperature improved with thermal pre-exposure (i.e., higher Fv/Fm), yet, this effect depended on host genotype and was influenced by active feeding as photochemical efficiency dropped in response to food deprivation. These findings highlight the role of temperature and partner fidelity in the establishment and performance of symbiosis and demonstrate the importance of heterotrophy for symbiotic cnidarians to endure and recover from stress.
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Li, Hsing-Hui, Jia-Lin Lu, Hui-Esther Lo, Sujune Tsai, and Chiahsin Lin. "Effect of Cryopreservation on Proteins from the Ubiquitous Marine Dinoflagellate Breviolum sp. (Family Symbiodiniaceae)." Plants 10, no. 8 (August 21, 2021): 1731. http://dx.doi.org/10.3390/plants10081731.
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Coral reefs around the world are exposed to thermal stress from climate change, disrupting the delicate symbiosis between the coral host and its symbionts. Cryopreservation is an indispensable tool for the preservation of species, as well as the establishment of a gene bank. However, the development of cryopreservation techniques for application to symbiotic algae is limited, in addition to the scarceness of related studies on the molecular level impacts post-thawing. Hence, it is essential to set up a suitable freezing protocol for coral symbionts, as well as to analyze its cryo-injury at the molecular level. The objective of this study was to develop a suitable protocol for the coral symbiont Breviolum subjected to two-step freezing. The thawed Breviolum were then cultured for 3, 7, 14, and 28 days before they were analyzed by Western blot for protein expression, light-harvesting protein (LHP), and red fluorescent protein (RFP) and tested by adenosine triphosphate bioassay for cell viability. The results showed the highest cell viability for thawed Breviolum that was treated with 2 M propylene glycol (PG) and 2 M methanol (MeOH) and equilibrated with both cryoprotectants for 30 min and 20 min. Both treatment groups demonstrated a significant increase in cell population after 28 days of culture post-thawing, especially for the MeOH treatment group, whose growth rate was twice of the PG treatment group. Regarding protein expression, the total amounts of each type of protein were significantly affected by cryopreservation. After 28 days of culture, the protein expression for the MeOH treatment group showed no significant difference to that of the control group, whereas the protein expression for the PG treatment group showed a significant difference. Breviolum that were frozen with MeOH recovered faster upon thawing than those frozen with PG. LHP was positively and RFP was negatively correlated with Symbiodiniaceae viability and so could serve as health-informing biomarkers. This work represents the first time to document it in Symbiodiniaceae, and this study established a suitable protocol for the cryopreservation of Breviolum and further refined the current understanding of the impact of low temperature on its protein expression. By gaining further understanding of the use of cryopreservation as a way to conserve Symbiodiniaceae, we hope to make an effort in the remediation and conservation of the coral reef ecosystem and provide additional methods to rescue coral reefs.
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Stanley, George D., and Jere H. Lipps. "Photosymbiosis: The Driving Force for Reef Success and Failure." Paleontological Society Papers 17 (October 2011): 33–59. http://dx.doi.org/10.1017/s1089332600002436.
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Photosymbiosis has been an important process in the evolution of ancient reef systems and in reef success today. Modern reefs and many of those in the geologic past inhabited nutrient-depleted settings. The complete collapse of some ancient reef ecosystems may be attributed to the breakdown of the ecologic and physiologic relationships between symbiont and host. Many algal groups developed symbioses with calcifying metazoans and protists and live with them, but the most common of these today are dinoflagellates in the genus Symbiodinium, sometimes called zooxanthellae. This photosymbiotic relationship conferred important metabolic advantages to both partners, allowing exploitation of tropical, shallow-water oligotrophic settings. In addition to improved metabolism, a by-product was rapid calcification which increased the growth of reefs and provided advantages to the hosts through larger and stronger skeletal support. Strong evolutionary pressures exerted by the symbiont-host relationship created bonds and favored longevity and adaptive novelty. Photosynthesis accounts for the remarkable reef growth and carbonate sedimentation in the tropics. Photosymbiosis gave reef organisms an adaptive edge to develop new life strategies that could not be developed by organisms which did not foster this relationship. Many living calcified organisms harbor many different photosymbionts and likely a variety of ancient calcified organisms did too (foraminifera, calcified sponges, corals, brachiopods and bivalve mollusks). Symbiodinium now a dominant symbiont apparently appeared in the Eocene and so was probably not utilized by earlier reef organisms, although the fossil record of dinoflagellates most closely related to Symbiodinium extends back to the Triassic. Today Symbiodinium inhabits a wide variety of unrelated host organisms from protists to mollusks. While the identity of more ancient photosymbionts is unclear, indirect evidence suggests photosymbiotic ecosystems existed as far back as the Proterozoic and possibly even earlier.Assessment of photosymbiosis in ancient reef ecosystems requires recognition of specific characteristics possessed by the calcifying reef organisms. Since the symbionts do not fossilize, the presence of photosymbiosis in fossils is a working hypothesis based on modern symbioses and best confirmed by a set of specific morphologic adaptations and isotopic analyses. Important among these is the thin tissue syndrome—the modification to achieve the “solar panel” effect. Large size and unusual or complex morphology also may indicate photosymbiosis. In the case of colonial organisms such as corals, high levels of corallite integration, where corallites are modified for increasing cooperation, may assist because most colonial photosymbiotic organisms today, such as corals, are exclusively photosymbiotic.Analysis of organisms and reefs through geologic time permits assessment of the strength of photosymbiosis as a driving force. Reef ecosystems revealing the strongest assessment for photosymbiosis are those of the mid-Paleozoic (Late Ordovician to Devonian), late Paleozoic, early Mesozoic and Neogene. The Early Cambrian archaeocyathan (sponge) reefs indicate photosymbiosis but perhaps with different ancient symbionts such as cyanobacteria, also contained in some modern sponges. Reef ecosystems of the late Paleozoic and early part of the Jurassic indicate the presence of some photosymbiosis. The extinction of many photosymbiotic reef ecosystems during critical intervals of mass extinctions may have been driven by the failure of the symbiosis or demise of the symbionts. Reef gaps in the geologic record reflect the absence of photosymbiosis. The present-day reef crisis involves disturbance of photosymbiosis, and study of future reef declines will benefit by application of data from the fossil record.
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Aihara, Yusuke, Shinichiro Maruyama, Andrew H. Baird, Akira Iguchi, Shunichi Takahashi, and Jun Minagawa. "Green fluorescence from cnidarian hosts attracts symbiotic algae." Proceedings of the National Academy of Sciences 116, no. 6 (January 22, 2019): 2118–23. http://dx.doi.org/10.1073/pnas.1812257116.
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Reef-building corals thrive in nutrient-poor marine environments because of an obligate symbiosis with photosynthetic dinoflagellates of the genusSymbiodinium. Symbiosis is established in most corals through the uptake ofSymbiodiniumfrom the environment. Corals are sessile for most of their life history, whereas free-livingSymbiodiniumare motile; hence, a mechanism to attractSymbiodiniumwould greatly increase the probability of encounter between host and symbiont. Here, we examined whether corals can attract free-living motileSymbiodiniumby their green fluorescence, emitted by the excitation of endogenous GFP by purple-blue light. We found thatSymbiodiniumhave positive and negative phototaxis toward weak green and strong purple-blue light, respectively. Under light conditions that cause corals to emit green fluorescence, (e.g., strong blue light),Symbiodiniumwere attracted toward live coral fragments.Symbiodiniumwere also attracted toward an artificial green fluorescence dye with similar excitation and emission spectra to coral-GFP. In the field, moreSymbiodiniumwere found in traps painted with a green fluorescence dye than in controls. Our results revealed a biological signaling mechanism between the coral host and its potential symbionts.
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Rosic, Nedeljka N., Mathieu Pernice, Simon Dunn, Sophie Dove, and Ove Hoegh-Guldberg. "Differential Regulation by Heat Stress of Novel Cytochrome P450 Genes from the Dinoflagellate Symbionts of Reef-Building Corals." Applied and Environmental Microbiology 76, no. 9 (March 12, 2010): 2823–29. http://dx.doi.org/10.1128/aem.02984-09.
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ABSTRACT Exposure to heat stress has been recognized as one of the major factors leading to the breakdown of the coral-alga symbiosis and coral bleaching. Here, we describe the presence of three new cytochrome P450 (CYP) genes from the reef-building coral endosymbiont Symbiodinium (type C3) and changes in their expression during exposure to severe and moderate heat stress conditions. Sequence analysis of the CYP C-terminal region and two conserved domains, the “PERF” and “heme-binding” domains, confirmed the separate identities of the CYP genes analyzed. In order to explore the effects of different heat stress scenarios, samples of the scleractinian coral Acropora millepora were exposed to elevated temperatures incrementally over an 18-h period (rapid thermal stress) and over a 120-h period (gradual thermal stress). After 18 h of gradual heating and incubation at 26°C, the Symbiodinium CYP mRNA pool was approximately 30% larger, while a further 6°C increase to a temperature above the average sea temperature (29°C after 72 h) resulted in a 2- to 4-fold increase in CYP expression. Both rapid heat stress and gradual heat stress at 32°C resulted in 50% to 90% decreases in CYP gene transcript abundance. Consequently, the initial upregulation of expression of CYP genes at moderately elevated temperatures (26°C and 29°C) was followed by a decrease in expression under the greater thermal stress conditions at 32°C. These findings indicate that in the coral-alga symbiosis under heat stress conditions there is production of chemical stressors and/or transcriptional factors that regulate the expression of genes, such as the genes encoding cytochrome P450 monooxygenases, that are involved in the first line of an organism's chemical defense.
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Karako-Lampert, S., D. J. Katcoff, Y. Achituv, Z. Dubinsky, and N. Stambler. "Do clades of symbiotic dinoflagellates in scleractinian corals of the Gulf of Eilat (Red Sea) differ from those of other coral reefs?" Journal of Experimental Marine Biology and Ecology 311, no. 2 (November 2004): 301–14. http://dx.doi.org/10.1016/j.jembe.2004.05.015.
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Matthews, Jennifer L., Camerron M. Crowder, Clinton A. Oakley, Adrian Lutz, Ute Roessner, Eli Meyer, Arthur R. Grossman, Virginia M. Weis, and Simon K. Davy. "Optimal nutrient exchange and immune responses operate in partner specificity in the cnidarian-dinoflagellate symbiosis." Proceedings of the National Academy of Sciences 114, no. 50 (November 20, 2017): 13194–99. http://dx.doi.org/10.1073/pnas.1710733114.
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The relationship between corals and dinoflagellates of the genusSymbiodiniumis fundamental to the functioning of coral ecosystems. It has been suggested that reef corals may adapt to climate change by changing their dominant symbiont type to a more thermally tolerant one, although the capacity for such a shift is potentially hindered by the compatibility of different host-symbiont pairings. Here we combined transcriptomic and metabolomic analyses to characterize the molecular, cellular, and physiological processes that underlie this compatibility, with a particular focus onSymbiodinium trenchii, an opportunistic, thermally tolerant symbiont that flourishes in coral tissues after bleaching events. Symbiont-free individuals of the sea anemoneExaiptasia pallida(commonly referred to as Aiptasia), an established model system for the study of the cnidarian-dinoflagellate symbiosis, were colonized with the “normal” (homologous) symbiontSymbiodinium minutumand the heterologousS. trenchii. Analysis of the host gene and metabolite expression profiles revealed that heterologous symbionts induced an expression pattern intermediate between the typical symbiotic state and the aposymbiotic state. Furthermore, integrated pathway analysis revealed that increased catabolism of fixed carbon stores, metabolic signaling, and immune processes occurred in response to the heterologous symbiont type. Our data suggest that both nutritional provisioning and the immune response induced by the foreign “invader” are important factors in determining the capacity of corals to adapt to climate change through the establishment of novel symbioses.
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Tremblay, P., M. Fine, J. F. Maguer, R. Grover, and C. Ferrier-Pagès. "Ocean acidification increases photosynthate translocation in a coral–dinoflagellates symbiosis." Biogeosciences Discussions 10, no. 1 (January 3, 2013): 83–109. http://dx.doi.org/10.5194/bgd-10-83-2013.
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Abstract. This study has examined the effect of an increased seawater pCO2 on the rates of photosynthesis and carbon translocation in the scleractinian coral species Stylophora pistillata using a new model based on 13C-labelling of the photosynthetic products. Symbiont photosynthesis contributes for a large part of the carbon acquisition in tropical coral species and is therefore an important process that may determine their survival under climate change scenarios. Nubbins of S. pistillata were maintained for six months under two pHs (8.1 and 7.2). Rates of photosynthesis and respiration of the symbiotic association and of isolated symbionts were assessed at each pH. The fate of 13C-photosynthates was then followed in the symbionts and the coral host for 48 h. Nubbins maintained at pH 7.2 presented a lower areal symbiont concentration, lower areal rates of gross photosynthesis, and lower carbon incorporation rates compared to nubbins maintained at pH 8.1, therefore suggesting that the total carbon acquisition was lower in this first set of nubbins. However, the total percentage of carbon translocated to the host, as well as the amount of carbon translocated per symbiont cell was significantly higher under pH 7.2 than under pH 8.1 (70% at pH 7.2 versus 60% at pH 8.1), so that the total amount of photosynthetic carbon received by the coral host was equivalent under both pHs (5.5 to 6.1 μg C cm−2 h−1). Although the carbon budget of the host was unchanged, symbionts acquired less carbon for their own needs (0.6 against 1.8 μg C cm−2 h−1), explaining the overall decrease in symbiont concentration at low pH. In the long-term, this decrease might have important consequences for the survival of corals under an acidification stress.
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Bourne, David G., Holly V. Boyett, Meegan E. Henderson, Andrew Muirhead, and Bette L. Willis. "Identification of a Ciliate (Oligohymenophorea: Scuticociliatia) Associated with Brown Band Disease on Corals of the Great Barrier Reef." Applied and Environmental Microbiology 74, no. 3 (December 14, 2007): 883–88. http://dx.doi.org/10.1128/aem.01124-07.
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ABSTRACT A ciliate associated with the coral disease brown band (BrB) was identified as a new species belonging to the class Oligohymenophorea, subclass Scuticociliatia. The ciliates were characterized by the presence of large numbers of intracellular dinoflagellates and displayed an elongated, tube-shaped body structure. They had uniform ciliature, except for three distinct cilia in the caudal region, and were typically 200 to 400 μm in length and 20 to 50 μm in width.
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Rosset, S., G. Koster, J. Brandsma, A. N. Hunt, A. D. Postle, and C. D’Angelo. "Lipidome analysis of Symbiodiniaceae reveals possible mechanisms of heat stress tolerance in reef coral symbionts." Coral Reefs 38, no. 6 (October 16, 2019): 1241–53. http://dx.doi.org/10.1007/s00338-019-01865-x.
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Abstract Climate change-induced global warming threatens the survival of key ecosystems including shallow water coral reefs. Elevated temperatures can disrupt the normal physiological functioning of photosynthetic organisms by altering the fluidity and permeability of chloroplast membranes that is defined and regulated by their lipid composition. Since the habitat-forming reef corals rely on the obligatory symbiosis with dinoflagellates of the family Symbiodiniaceae, their heat stress response can be expected to be strongly influenced by the symbiont's lipid metabolism. However, in contrast to the steady increase in the knowledge of the functioning of coral symbionts at the genomic and transcriptomic level, the understanding of their membrane lipid composition and regulation in response to temperature stress is lagging behind. We have utilised mass spectrometry-based lipidomic analyses to identify the key polar lipids that form the biological membranes of reef coral symbionts, comparing the thermotolerant species Durusdinium trenchii with the thermosensitive taxon Cladocopium C3, both hosted by Acropora valida. Our results indicate that the superior thermotolerance D. trenchii inside the host corals could be achieved through (1) the amount and saturation of sulfoquinovosyldiacylglycerols, in particular through putative photosystem II interactions, (2) the increased digalactosyldiacylglycerol to monogalactosyldiacylglycerol ratio with the potential to stabilise thylakoid membranes and integrated proteins, and (3) the chaperone-like function of lyso-lipids. Thereby, our study provides novel insights into the heat tolerance of coral symbionts, contributing to the understanding of the potential of coral reef ecosystems to respond and adjust to heat stress events that are becoming more frequent due to climate change. Finally, our identification of multiple mechanisms of heat tolerance in Symbiodiniaceae furthers the knowledge of the general stress physiology of photosynthetic organisms.
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Cornwell, Brendan H., and Luis Hernández. "Genetic structure in the endosymbiont Breviolum ‘muscatinei’ is correlated with geographical location, environment and host species." Proceedings of the Royal Society B: Biological Sciences 288, no. 1946 (March 10, 2021): 20202896. http://dx.doi.org/10.1098/rspb.2020.2896.
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Corals and cnidarians form symbioses with dinoflagellates across a wide range of habitats from the tropics to temperate zones. Notably, these partnerships create the foundation of coral reef ecosystems and are at risk of breaking down due to climate change. This symbiosis couples the fitness of the partners, where adaptations in one species can benefit the holobiont. However, the scales over which each partner can match their current—and future—environment are largely unknown. We investigated population genetic patterns of temperate anemones ( Anthopleura spp.) and their endosymbiont Breviolum ‘muscatinei’ , across an extensive geographical range to identify the spatial scales over which local adaptation is possible. Similar to previously published results, two solitary host species exhibited isolation by distance across hundreds of kilometres. However, symbionts exhibited genetic structure across multiple spatial scales, from geographical location to depth in the intertidal zone, and host species, suggesting that symbiont populations are more likely than their hosts to adaptively mitigate the impact of increasing temperatures.
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Krueger, Thomas, Noa Horwitz, Julia Bodin, Maria-Evangelia Giovani, Stéphane Escrig, Anders Meibom, and Maoz Fine. "Common reef-building coral in the Northern Red Sea resistant to elevated temperature and acidification." Royal Society Open Science 4, no. 5 (May 2017): 170038. http://dx.doi.org/10.1098/rsos.170038.
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Coral reefs are currently experiencing substantial ecological impoverishment as a result of anthropogenic stressors, and the majority of reefs are facing immediate risk. Increasing ocean surface temperatures induce frequent coral mass bleaching events—the breakdown of the nutritional photo-symbiosis with intracellular algae (genus: Symbiodinium ). Here, we report that Stylophora pistillata from a highly diverse reef in the Gulf of Aqaba showed no signs of bleaching despite spending 1.5 months at 1–2°C above their long-term summer maximum (amounting to 11 degree heating weeks) and a seawater pH of 7.8. Instead, their symbiotic dinoflagellates exhibited improved photochemistry, higher pigmentation and a doubling in net oxygen production, leading to a 51% increase in primary productivity. Nanoscale secondary ion mass spectrometry imaging revealed subtle cellular-level shifts in carbon and nitrogen metabolism under elevated temperatures, but overall host and symbiont biomass proxies were not significantly affected. Now living well below their thermal threshold in the Gulf of Aqaba, these corals have been evolutionarily selected for heat tolerance during their migration through the warm Southern Red Sea after the last ice age. This may allow them to withstand future warming for a longer period of time, provided that successful environmental conservation measures are enacted across national boundaries in the region.
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ZHOU, Guo-Wei, and Hui HUANG. "Low genetic diversity of symbiotic dinoflagellates (Symbiodinium) in scleractinian corals from tropical reefs in southern Hainan Island, China." Journal of Systematics and Evolution 49, no. 6 (October 6, 2011): 598–605. http://dx.doi.org/10.1111/j.1759-6831.2011.00161.x.
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Kishimoto, Mariko, Andrew H. Baird, Shinichiro Maruyama, Jun Minagawa, and Shunichi Takahashi. "Loss of symbiont infectivity following thermal stress can be a factor limiting recovery from bleaching in cnidarians." ISME Journal 14, no. 12 (August 21, 2020): 3149–52. http://dx.doi.org/10.1038/s41396-020-00742-8.
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Abstract Increases in seawater temperature can cause coral bleaching through loss of symbiotic algae (dinoflagellates of the family Symbiodiniaceae). Corals can recover from bleaching by recruiting algae into host cells from the residual symbiont population or from the external environment. However, the high coral mortality that often follows mass-bleaching events suggests that recovery is often limited in the wild. Here, we examine the effect of pre-exposure to heat stress on the capacity of symbiotic algae to infect cnidarian hosts using the Aiptasia (sea-anemone)-Symbiodiniaceae model system. We found that the symbiont strain Breviolum sp. CS-164 (ITS2 type B1), both free-living and in symbiosis, loses the capacity to infect the host following exposure to heat stress. This loss of infectivity is reversible, however, a longer exposure to heat stress increases the time taken for reversal. Under the same experimental conditions, the loss of infectivity was not observed in another strain Breviolum psygmophilum CCMP2459 (ITS2 type B2). Our results suggest that recovery from bleaching can be limited by the loss of symbiont infectivity following exposure to heat stress.
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Harii, Saki, Masanobu Yamamoto, and Ove Hoegh-Guldberg. "The relative contribution of dinoflagellate photosynthesis and stored lipids to the survivorship of symbiotic larvae of the reef-building corals." Marine Biology 157, no. 6 (February 18, 2010): 1215–24. http://dx.doi.org/10.1007/s00227-010-1401-0.
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González-Pech, Raúl A., Timothy G. Stephens, Yibi Chen, Amin R. Mohamed, Yuanyuan Cheng, Sarah Shah, Katherine E. Dougan, et al. "Comparison of 15 dinoflagellate genomes reveals extensive sequence and structural divergence in family Symbiodiniaceae and genus Symbiodinium." BMC Biology 19, no. 1 (April 13, 2021). http://dx.doi.org/10.1186/s12915-021-00994-6.
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Abstract Background Dinoflagellates in the family Symbiodiniaceae are important photosynthetic symbionts in cnidarians (such as corals) and other coral reef organisms. Breakdown of the coral-dinoflagellate symbiosis due to environmental stress (i.e. coral bleaching) can lead to coral death and the potential collapse of reef ecosystems. However, evolution of Symbiodiniaceae genomes, and its implications for the coral, is little understood. Genome sequences of Symbiodiniaceae remain scarce due in part to their large genome sizes (1–5 Gbp) and idiosyncratic genome features. Results Here, we present de novo genome assemblies of seven members of the genus Symbiodinium, of which two are free-living, one is an opportunistic symbiont, and the remainder are mutualistic symbionts. Integrating other available data, we compare 15 dinoflagellate genomes revealing high sequence and structural divergence. Divergence among some Symbiodinium isolates is comparable to that among distinct genera of Symbiodiniaceae. We also recovered hundreds of gene families specific to each lineage, many of which encode unknown functions. An in-depth comparison between the genomes of the symbiotic Symbiodinium tridacnidorum (isolated from a coral) and the free-living Symbiodinium natans reveals a greater prevalence of transposable elements, genetic duplication, structural rearrangements, and pseudogenisation in the symbiotic species. Conclusions Our results underscore the potential impact of lifestyle on lineage-specific gene-function innovation, genome divergence, and the diversification of Symbiodinium and Symbiodiniaceae. The divergent features we report, and their putative causes, may also apply to other microbial eukaryotes that have undergone symbiotic phases in their evolutionary history.
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Tortorelli, Giada, Carsten Rautengarten, Antony Bacic, Gabriela Segal, Berit Ebert, Simon K. Davy, Madeleine J. H. van Oppen, and Geoffrey I. McFadden. "Cell surface carbohydrates of symbiotic dinoflagellates and their role in the establishment of cnidarian–dinoflagellate symbiosis." ISME Journal, July 20, 2021. http://dx.doi.org/10.1038/s41396-021-01059-w.
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AbstractSymbiodiniaceae algae are often photosymbionts of reef-building corals. The establishment of their symbiosis resembles a microbial infection where eukaryotic pattern recognition receptors (e.g. lectins) are thought to recognize a specific range of taxon-specific microbial-associated molecular patterns (e.g. glycans). The present study used the sea anemone, Exaiptasia diaphana and three species of Symbiodiniaceae (the homologous Breviolum minutum, the heterologous-compatible Cladocopium goreaui and the heterologous-incompatible Fugacium kawagutii) to compare the surface glycomes of three symbionts and explore the role of glycan–lectin interactions in host–symbiont recognition and establishment of symbiosis. We identified the nucleotide sugars of the algal cells, then examined glycans on the cell wall of the three symbiont species with monosaccharide analysis, lectin array technology and fluorescence microscopy of the algal cell decorated with fluorescently tagged lectins. Armed with this inventory of possible glycan moieties, we then assayed the ability of the three Symbiodiniaceae to colonize aposymbiotic E. diaphana after modifying the surface of one of the two partners. The Symbiodiniaceae cell-surface glycome varies among algal species. Trypsin treatment of the alga changed the rate of B. minutum and C. goreaui uptake, suggesting that a protein-based moiety is an essential part of compatible symbiont recognition. Our data strongly support the importance of D-galactose (in particular β-D-galactose) residues in the establishment of the cnidarian–dinoflagellate symbiosis, and we propose a potential involvement of L-fucose, D-xylose and D-galacturonic acid in the early steps of this mutualism.
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Goulet, Tamar L., and Denis Goulet. "Climate Change Leads to a Reduction in Symbiotic Derived Cnidarian Biodiversity on Coral Reefs." Frontiers in Ecology and Evolution 9 (March 30, 2021). http://dx.doi.org/10.3389/fevo.2021.636279.
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Symbiotic relationships enable partners to thrive and survive in habitats where they would either not be as successful, or potentially not exist, without the symbiosis. The coral reef ecosystem, and its immense biodiversity, relies on the symbioses between cnidarians (e.g., scleractinian corals, octocorals, sea anemones, jellyfish) and multiple organisms including dinoflagellate algae (family Symbiodiniaceae), bivalves, crabs, shrimps, and fishes. In this review, we discuss the ramifications of whether coral reef cnidarian symbioses are obligatory, whereby at least one of the partners must be in the symbiosis in order to survive or are facultative. Furthermore, we cover the consequences of cnidarian symbioses exhibiting partner flexibility or fidelity. Fidelity, where a symbiotic partner can only engage in symbiosis with a subset of partners, may be absolute or context dependent. Current literature demonstrates that many cnidarian symbioses are highly obligative and appear to exhibit absolute fidelity. Consequently, for many coral reef cnidarian symbioses, surviving changing environmental conditions will depend on the robustness and potential plasticity of the existing host-symbiont(s) combination. If environmental conditions detrimentally affect even one component of this symbiotic consortium, it may lead to a cascade effect and the collapse of the entire symbiosis. Symbiosis is at the heart of the coral reef ecosystem, its existence, and its high biodiversity. Climate change may cause the demise of some of the cnidarian symbioses, leading to subsequent reduction in biodiversity on coral reefs.
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Kawamura, Kaz, Satoko Sekida, Koki Nishitsuji, Eiichi Shoguchi, Kanako Hisata, Shigeki Fujiwara, and Noriyuki Satoh. "In vitro Symbiosis of Reef-Building Coral Cells With Photosynthetic Dinoflagellates." Frontiers in Marine Science 8 (July 14, 2021). http://dx.doi.org/10.3389/fmars.2021.706308.
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Coral reefs are the biodiversity hot spots of the oceans, but they have suffered from increasing environmental stresses caused principally by anthropogenic global warming. The keystone species of coral reefs are scleractinian corals, which maintain obligatory symbiotic relationships with photosynthetic dinoflagellates. Understanding cellular and molecular mechanisms of symbiosis is therefore essential for future preservation of coral reefs. To date, however, almost no in vitro experimental systems have been devised to illuminate such mechanisms. To this end, our previous study established stable in vitro cell culture lines, including IVB5, originating from planula larvae of the scleractinian coral, Acropora tenuis. Here, we show that soon after mixture with the dinoflagellate, Breviolum minutum, flattened amorphous coral cells with endodermal properties exhibited elevated locomotor activity using filopodia and lamellipodia and interacted with dinoflagellates. Several minutes thereafter, coral cells began to incorporate B. minutum, and in vitro symbiosis appeared to have been accomplished within 30 min. Nearly a half of the coral cells had incorporated algal cells within 24 h in a reproducible manner. Coral cells that harbored algal cells gradually became round and less mobile, and the algal cells sometimes settled in vacuole-like structures in coral cell cytoplasm. This symbiosis state was maintained for at least a month. The IVB5 line of A. tenuis therefore provides an experimental system to explore cellular and molecular mechanisms involved in coral-dinoflagellate symbiosis at the single-cell level, results of which may be useful for future preservation of coral reefs.
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Kemp, Dustin W., Stephen C. Kempf, and William K. Fitt. "The weight of it all: symbiotic dinoflagellates in Caribbean reef-building corals." Marine Biology 167, no. 8 (July 26, 2020). http://dx.doi.org/10.1007/s00227-020-03737-3.
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Grupstra, Carsten G. B., Kristen M. Rabbitt, Lauren I. Howe-Kerr, and Adrienne M. S. Correa. "Fish predation on corals promotes the dispersal of coral symbionts." Animal Microbiome 3, no. 1 (March 22, 2021). http://dx.doi.org/10.1186/s42523-021-00086-4.
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Abstract Background The microbiomes of foundation (habitat-forming) species such as corals and sponges underpin the biodiversity, productivity, and stability of ecosystems. Consumers shape communities of foundation species through trophic interactions, but the role of consumers in dispersing the microbiomes of such species is rarely examined. For example, stony corals rely on a nutritional symbiosis with single-celled endosymbiotic dinoflagellates (family Symbiodiniaceae) to construct reefs. Most corals acquire Symbiodiniaceae from the environment, but the processes that make Symbiodiniaceae available for uptake are not resolved. Here, we provide the first comprehensive, reef-scale demonstration that predation by diverse coral-eating (corallivorous) fish species promotes the dispersal of Symbiodiniaceae, based on symbiont cell densities and community compositions from the feces of four obligate corallivores, three facultative corallivores, two grazer/detritivores as well as samples of reef sediment and water. Results Obligate corallivore feces are environmental hotspots of Symbiodiniaceae cells: live symbiont cell concentrations in such feces are 5–7 orders of magnitude higher than sediment and water environmental reservoirs. Symbiodiniaceae community compositions in the feces of obligate corallivores are similar to those in two locally abundant coral genera (Pocillopora and Porites), but differ from Symbiodiniaceae communities in the feces of facultative corallivores and grazer/detritivores as well as sediment and water. Combining our data on live Symbiodiniaceae cell densities in feces with in situ observations of fish, we estimate that some obligate corallivorous fish species release over 100 million Symbiodiniaceae cells per 100 m2 of reef per day. Released corallivore feces came in direct contact with coral colonies in the fore reef zone following 91% of observed egestion events, providing a potential mechanism for the transfer of live Symbiodiniaceae cells among coral colonies. Conclusions Taken together, our findings show that fish predation on corals may support the maintenance of coral cover on reefs in an unexpected way: through the dispersal of beneficial coral symbionts in corallivore feces. Few studies examine the processes that make symbionts available to foundation species, or how environmental reservoirs of such symbionts are replenished. This work sets the stage for parallel studies of consumer-mediated microbiome dispersal and assembly in other sessile, habitat-forming species.
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Yu, Liying, Tangcheng Li, Ling Li, Xin Lin, Hongfei Li, Chichi Liu, Chentao Guo, and Senjie Lin. "SAGER: a database of Symbiodiniaceae and Algal Genomic Resource." Database 2020 (January 1, 2020). http://dx.doi.org/10.1093/database/baaa051.
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Abstract Symbiodiniaceae dinoflagellates are essential endosymbionts of reef building corals and some other invertebrates. Information of their genome structure and function is critical for understanding coral symbiosis and bleaching. With the rapid development of sequencing technology, genome draft assemblies of several Symbiodiniaceae species and diverse marine algal genomes have become publicly available but spread in multiple separate locations. Here, we present a Symbiodiniaceae and Algal Genomic Resource Database (SAGER), a user-friendly online repository for integrating existing genomic data of Symbiodiniaceae species and diverse marine algal gene sets from MMETSP and PhyloDB databases. Relevant algal data are included to facilitate comparative analyses. The database is freely accessible at http://sampgr.org.cn. It provides comprehensive tools for studying gene function, expression and comparative genomics, including search tools to identify gene information from Symbiodiniaceae species, and BLAST tool to find orthologs from marine algae and protists. Moreover, SAGER integrates transcriptome datasets derived from diverse culture conditions of corresponding Symbiodiniaceae species. SAGER was developed with the capacity to incorporate future Symbiodiniaceae and algal genome and transcriptome data, and will serve as an open-access and sustained platform providing genomic and molecular tools that can be conveniently used to study Symbiodiniaceae and other marine algae. Database URL: http://sampgr.org.cn