Photosynthetic Endosymbionts Research Articles

Architecture of symbiotic dinoflagellate photosystem I–light-harvesting supercomplex in Symbiodinium

Symbiodinium are the photosynthetic endosymbionts for corals and play a vital role in supplying their coral hosts with photosynthetic products, forming the nutritional foundation for high-yield coral reef ecosystems. Here, we determine the cryo-electron microscopy structure of Symbiodinium photosystem I (PSI) supercomplex with a PSI core composed of 13 subunits including 2 previously unidentified subunits, PsaT and PsaU, as well as 13 peridinin-Chl a/c-binding light-harvesting antenna proteins (AcpPCIs). The PSI–AcpPCI supercomplex exhibits distinctive structural features compared to their red lineage counterparts, including extended termini of PsaD/E/I/J/L/M/R and AcpPCI-1/3/5/7/8/11 subunits, conformational changes in the surface loops of PsaA and PsaB subunits, facilitating the association between the PSI core and peripheral antennae. Structural analysis and computational calculation of excitation energy transfer rates unravel specific pigment networks in Symbiodinium PSI–AcpPCI for efficient excitation energy transfer. Overall, this study provides a structural basis for deciphering the mechanisms governing light harvesting and energy transfer in Symbiodinium PSI–AcpPCI supercomplexes adapted to their symbiotic ecosystem, as well as insights into the evolutionary diversity of PSI–LHCI among various photosynthetic organisms.

Cellular plasticity facilitates phenotypic change in a dominant coral’s Symbiodiniaceae assemblage

Coral-associated dinoflagellates (Symbiodiniaceae) are photosynthetic endosymbionts that influence coral acclimation, as indicated by photo-endosymbiotic phenotypic variance across different environmental conditions. Symbiont shuffling (shifts in endosymbiont community composition), changes in endosymbiont cell density, and cellular plasticity have all been proposed as acclimation mechanisms. However, few studies have been able to partition which of the three strategies were responsible for observed phenotypic variance. Using a combination of metabarcoding and flow cytometry, we simultaneously characterized Acropora pulchra-associated Symbiodiniaceae assemblages at the community, population, and individual level under natural environmental conditions to deduce whether seasonal phenotypic change and site-related phenotypic variation of Symbiodiniaceae assemblages is a product of symbiont shuffling or cellular plasticity. Symbiodiniaceae assemblages displayed season-specific phenotypic variance, while Symbiodiniaceae community composition was geographically structured and cell density showed limited data structure. Based on these patterns, we reveal that cellular plasticity of Symbiodiniaceae was the source of a phenotypic variation, thus indicating that cellular plasticity is a mechanism for acclimation to mild environmental change.

#DeOlhoNosCorais: a polygonal annotated dataset to optimize coral monitoring.

Corals are colonial animals within the Phylum Cnidaria that form coral reefs, playing a significant role in marine environments by providing habitat for fish, mollusks, crustaceans, sponges, algae, and other organisms. Global climate changes are causing more intense and frequent thermal stress events, leading to corals losing their color due to the disruption of a symbiotic relationship with photosynthetic endosymbionts. Given the importance of corals to the marine environment, monitoring coral reefs is critical to understanding their response to anthropogenic impacts. Most coral monitoring activities involve underwater photographs, which can be costly to generate on large spatial scales and require processing and analysis that may be time-consuming. The Marine Ecology Laboratory (LECOM) at the Federal University of Rio Grande do Norte (UFRN) developed the project "#DeOlhoNosCorais" which encourages users to post photos of coral reefs on their social media (Instagram) using this hashtag, enabling people without previous scientific training to contribute to coral monitoring. The laboratory team identifies the species and gathers information on coral health along the Brazilian coast by analyzing each picture posted on social media. To optimize this process, we conducted baseline experiments for image classification and semantic segmentation. We analyzed the classification results of three different machine learning models using the Local Interpretable Model-agnostic Explanations (LIME) algorithm. The best results were achieved by combining EfficientNet for feature extraction and Logistic Regression for classification. Regarding semantic segmentation, the U-Net Pix2Pix model produced a pixel-level accuracy of 86%. Our results indicate that this tool can enhance image selection for coral monitoring purposes and open several perspectives for improving classification performance. Furthermore, our findings can be expanded by incorporating other datasets to create a tool that streamlines the time and cost associated with analyzing coral reef images across various regions.

Molecular tuning of sea anemone stinging.

Jellyfish and sea anemones fire single-use, venom-covered barbs to immobilize prey or predators. We previously showed that the anemone Nematostella vectensis uses a specialized voltage-gated calcium (CaV) channel to trigger stinging in response to synergistic prey-derived chemicals and touch (Weir et al., 2020). Here, we use experiments and theory to find that stinging behavior is suited to distinct ecological niches. We find that the burrowing anemone Nematostella uses uniquely strong CaV inactivation for precise control of predatory stinging. In contrast, the related anemone Exaiptasia diaphana inhabits exposed environments to support photosynthetic endosymbionts. Consistent with its niche, Exaiptasia indiscriminately stings for defense and expresses a CaV splice variant that confers weak inactivation. Chimeric analyses reveal that CaVβ subunit adaptations regulate inactivation, suggesting an evolutionary tuning mechanism for stinging behavior. These findings demonstrate how functional specialization of ion channel structure contributes to distinct organismal behavior.

Molecular tuning of sea anemone stinging

Jellyfish and sea anemones fire single-use, venom-covered barbs to immobilize prey or predators. We previously showed that the anemone Nematostella vectensis uses a specialized voltage-gated calcium (CaV) channel to trigger stinging in response to synergistic prey-derived chemicals and touch (Weir et al., 2020). Here, we use experiments and theory to find that stinging behavior is suited to distinct ecological niches. We find that the burrowing anemone Nematostella uses uniquely strong CaV inactivation for precise control of predatory stinging. In contrast, the related anemone Exaiptasia diaphana inhabits exposed environments to support photosynthetic endosymbionts. Consistent with its niche, Exaiptasia indiscriminately stings for defense and expresses a CaV splice variant that confers weak inactivation. Chimeric analyses reveal that CaVβ subunit adaptations regulate inactivation, suggesting an evolutionary tuning mechanism for stinging behavior. These findings demonstrate how functional specialization of ion channel structure contributes to distinct organismal behavior.

Temperature as a factor controlling geographical distribution of greenNoctiluca scintillansin Southeast Asia

AbstractThe dinoflagellate Noctiluca scintillans exists in two forms, green and red Noctiluca, with and without the photosynthetic endosymbiont Pedinomonas noctilucae, respectively. In Southeast Asia, green Noctiluca has a northern boundary of distribution in the Luzon Strait and the Vietnamese coast, approximately corresponding to the 25°C isotherm. We examined whether this boundary arose from the growth dependence of Noctiluca on temperature and/or that of P. noctilucae. We analyzed the effect of temperature on growth by examining one and four unialgal cultures of red and green Noctiluca, respectively, and two monocultures of the endosymbiont. Growth dependence on temperature was markedly different between host cells of green Noctiluca and monocultures of the endosymbiont, although some variations in growing temperature were observed among strains of both Noctiluca and the endosymbiont. Green Noctiluca grew at a temperature range of 20–31°C, whereas P. noctilucae did not grow at low temperatures ≤25°C. Growth rates of green Noctiluca were considerably higher when fed compared to monocultures. Our findings demonstrate that the effect of temperature on P. noctilucae growth is a crucial factor controlling the geographical distribution of green Noctiluca in the South China Sea. An implication of this finding is discussed in the context of global warming.

The mesoglea buffers the physico-chemical microenvironment of photosymbionts in the upside-down jellyfish Cassiopea sp.

IntroductionThe jellyfish Cassiopea has a conspicuous lifestyle, positioning itself upside-down on sediments in shallow waters thereby exposing its photosynthetic endosymbionts (Symbiodiniaceae) to light. Several studies have shown how the photosymbionts benefit the jellyfish host in terms of nutrition and O2 availability, but little is known about the internal physico-chemical microenvironment of Cassiopea during light–dark periods.MethodsHere, we used fiber-optic sensors to investigate how light is modulated at the water-tissue interface of Cassiopea sp. and how light is scattered inside host tissue. We additionally used electrochemical and fiber-optic microsensors to investigate the dynamics of O2 and pH in response to changes in the light availability in intact living specimens of Cassiopea sp.Results and discussionMapping of photon scalar irradiance revealed a distinct spatial heterogeneity over different anatomical structures of the host, where oral arms and the manubrium had overall higher light availability, while shaded parts underneath the oral arms and the bell had less light available. White host pigmentation, especially in the bell tissue, showed higher light availability relative to similar bell tissue without white pigmentation. Microprofiles of scalar irradiance into white pigmented bell tissue showed intense light scattering and enhanced light penetration, while light was rapidly attenuated over the upper 0.5 mm in tissue with symbionts only. Depth profiles of O2 concentration into bell tissue of live jellyfish showed increasing concentration with depth into the mesoglea, with no apparent saturation point during light periods. O2 was slowly depleted in the mesoglea in darkness, and O2 concentration remained higher than ambient water in large (> 6 cm diameter) individuals, even after 50 min in darkness. Light–dark shifts in large medusae showed that the mesoglea slowly turns from a net sink during photoperiods into a net source of O2 during darkness. In contrast, small medusae showed a more dramatic change in O2 concentration, with rapid O2 buildup/consumption in response to light–dark shifts; in a manner similar to corals. These effects on O2 production/consumption were also reflected in moderate pH fluctuations within the mesoglea. The mesoglea thus buffers O2 and pH dynamics during dark-periods.

A global analysis of coral bleaching patterns in association with mangrove environments under global warming

Marine heatwaves caused by global warming are progressively degrading coral reefs worldwide via the process of coral bleaching – the expulsion of photosynthetic endosymbionts. However, coral bleaching is not spatially homogeneous, but varies across environmental gradients in association with local conditions and taxonomic composition. Emerging evidence suggests that mangrove habitats are recurrent ‘'microenvironments' for reef corals, providing key biogeochemical services believed to influence their resilience, and housing co‐tolerant coral taxa. This close association between coral reefs and mangroves has led to the hypothesis that the extent of coral bleaching is reduced by the proximity of reef building corals to mangroves. Here, we present the first global‐scale test addressing this hypothesis. Using Bayesian generalised linear mixed effect modelling, we show that coral bleaching tends to increase under higher thermal stress when corals are further away from mangroves. When comparing conditional effects, corals furthest away from mangroves also show the highest levels of bleaching, suggesting a phenomenon of reduced bleaching for corals residing closer to mangroves under thermal stress. The drivers of this pattern may be numerous, but most likely include the presence of co‐tolerant coral species which are known to be associated with mangroves. Future research should focus on disentangling the mechanisms underlying these coral bleaching patterns in association with mangroves, specifically focusing on in‐situ environmental and taxonomic data collection. These endeavours will most likely require high‐resolution analyses of coral reefs at more local‐scales. Ultimately, our findings add to the ever‐growing importance of mangroves for near‐shore coral reef environments, and suggest a potentially important benefit for coral reefs associated with mangroves in the Anthropocene.

Modeling food dependent symbiosis in Exaiptasia pallida

Cnidaria, marine invertebrates that include reef-building stony corals, often rely on photosynthetic endosymbionts to obtain the energy they need for growth. Increased temperatures and/or nutrient pollution can disrupt mutualistic properties of the symbiosis, leading to host mortality. However, the precise mechanism by which this dysbiosis occurs is still unclear. Sea anemones, other cnidarians that may host algal endosymbionts, are used as a model organism for the coral holobiont to understand the costs and benefits of symbionts, but the exact nature of the costs of symbionts on the hosts is still unclear. Here we developed a Dynamic Energy Budget (DEB) model and fit the model to data from the anemone Exaiptasia pallida and its endosymbiotic algae, Breviolum minutum, in order to identify the most likely mechanism of symbiont costs. In order to match the laboratory dataset, our model needed an explicit symbiont demand term, in which the symbiont can “consume” host tissue to forcibly extract nitrogen. The model demonstrates the role of the symbiont as an amplifier of the host’s state: a growing anemone grows better with symbionts, while a malnourished anemone looses biomass faster with a symbiont than without. This model allows us to project Cnidaria holobiont growth as a function of environmental conditions and adds a new framework for which to capture the direct cost a symbiont has on Cnidaria hosts.

Assessing the Trophic Impact of Bleaching: The Model Pair Berghia stephanieae/Exaiptasia diaphana.

Bleaching events associated with climate change are increasing worldwide, being a major threat to tropical coral reefs. Nonetheless, the indirect impacts promoted by the bleaching of organisms hosting photosynthetic endosymbionts, such as those impacting trophic interactions, have received considerably less attention by the scientific community. Bleaching significantly affects the nutritional quality of bleached organisms. The consequences promoted by such shifts remain largely overlooked, namely on specialized predators that have evolved to prey upon organisms hosting photosynthetic endosymbionts and benefit nutritionally, either directly or indirectly, from the available pool of photosynthates. In the present study, we advocate the use of the model predator-prey pair featuring the stenophagous nudibranch sea slug Berghia stephanieae that preys upon the photosymbiotic glass anemone Exaiptasia diaphana to study the impacts of bleaching on trophic interactions. These model organisms are already used in other research fields, and one may benefit from knowledge available on their physiology, omics, and culture protocols under controlled laboratory conditions. Moreover, B. stephanieae can thrive on either photosymbiotic or aposymbiotic (bleached) glass anemones, which can be easily maintained over long periods in the laboratory (unlike photosymbiotic corals). As such, one can investigate if and how nutritional shifts induced by bleaching impact highly specialized predators (stenophagous species), as well as if and how such effects cascade over consecutive generations. Overall, by using this model predator-prey pair one can start to truly unravel the trophic effects of bleaching events impacting coral reef communities, as well as their prevalence over time.

Insights on the biochemical and cellular changes induced by heat stress in the Cladocopium isolated from coral Mussismilia braziliensis.

Corals are treatened by global warming. Bleaching is one immediate effect of global warming, resulting from the loss of photosynthetic endosymbiont dinoflagellates. Understanding host-symbiont associations are critical for assessing coral’s habitat requirements and its response to environmental changes. Cladocopium (formerly family Symbiodiniaceae clade C) are dominant endosymbionts in the reef-building coral, Mussismilia braziliensis. This study aimed to investigate the effect of temperature on the biochemical and cellular features of Cladocopium. Heat stress increased oxygen (O2) and decreased proteins, pigments (Chla + Chlc2), hexadecanoic acid- methyl ester, methyl stearate, and octadecenoic acid (Z)- methyl ester molecules. In addition, there was an increase in neutral lipids such as esterified cholesterol and a decrease in free fatty acids that may have been incorporated for the production of lipid droplets. Transmission electron microscopy (TEM) demonstrated that Cladocopium cells subjected to heat stress had thinner cell walls, deformation of chloroplasts, and increased lipid droplets after 3 days at 28°C. These findings indicate that thermal stress negatively affects isolated Cladocopium spp. from Mussismilia host coral.

Marine protected areas do not buffer corals from bleaching under global warming

BackgroundThe rising temperature of the oceans has been identified as the primary driver of mass coral reef declines via coral bleaching (expulsion of photosynthetic endosymbionts). Marine protected areas (MPAs) have been implemented throughout the oceans with the aim of mitigating the impact of local stressors, enhancing fish biomass, and sustaining biodiversity overall. In coral reef regions specifically, protection from local stressors and the enhanced ecosystem function contributed by MPAs are expected to increase coral resistance to global-scale stressors such as marine heatwaves. However, MPAs still suffer from limitations in design, or fail to be adequately enforced, potentially reducing their intended efficacy. Here, we address the hypothesis that the local-scale benefits resulting from MPAs moderate coral bleaching under global warming related stress.ResultsBayesian analyses reveal that bleaching is expected to occur in both larger and older MPAs when corals are under thermal stress from marine heatwaves (quantified as Degree Heating Weeks, DHW), but this is partially moderated in comparison to the effects of DHW alone. Further analyses failed to identify differences in bleaching prevalence in MPAs relative to non-MPAs for coral reefs experiencing different levels of thermal stress. Finally, no difference in temperatures where bleaching occurs between MPA and non-MPA sites was found.ConclusionsOur findings suggest that bleaching is likely to occur under global warming regardless of protected status. Thus, while protected areas have key roles for maintaining ecosystem function and local livelihoods, combatting the source of global warming remains the best way to prevent the decline of coral reefs via coral bleaching.

Engineering artificial photosynthetic life-forms through endosymbiosis

The evolutionary origin of the photosynthetic eukaryotes drastically altered the evolution of complex lifeforms and impacted global ecology. The endosymbiotic theory suggests that photosynthetic eukaryotes evolved due to endosymbiosis between non-photosynthetic eukaryotic host cells and photosynthetic cyanobacterial or algal endosymbionts. The photosynthetic endosymbionts, propagating within the cytoplasm of the host cells, evolved, and eventually transformed into chloroplasts. Despite the fundamental importance of this evolutionary event, we have minimal understanding of this remarkable evolutionary transformation. Here, we design and engineer artificial, genetically tractable, photosynthetic endosymbiosis between photosynthetic cyanobacteria and budding yeasts. We engineer various mutants of model photosynthetic cyanobacteria as endosymbionts within yeast cells where, the engineered cyanobacteria perform bioenergetic functions to support the growth of yeast cells under defined photosynthetic conditions. We anticipate that these genetically tractable endosymbiotic platforms can be used for evolutionary studies, particularly related to organelle evolution, and also for synthetic biology applications.

Local anthropogenic stress does not exacerbate coral bleaching under global climate change

AbstractAimRising ocean temperatures are widely recognized as the dominant driver behind the rapid degradation of coral reefs via the process of coral bleaching (the expulsion of photosynthetic endosymbionts, which reveals the coral skeleton). However, bleaching of hard corals is often assumed to be further aggravated by the effect of local‐scale stressors from anthropogenic activity, accelerating coral reef decline where these stressors are stronger. Despite the importance of this hypothesis, the interaction between climate change and local stressors for driving coral bleaching has only been investigated in a handful of studies, with no large scale (regional or global) test conducted thus far. We investigate the impact of human population density (HPD) – a proxy for local stressors – in both protected and non‐protected marine regions, and their interaction under heat stress as drivers of coral bleaching.LocationGlobal.Time period2002–2018.Major taxa studiedScleractinia corals.MethodsUsing 9,170 coral reef surveys worldwide, we performed Bayesian modelling to assess the probability of coral bleaching in response to local‐scale stressors in interaction with global warming.ResultsLocal HPD does not exacerbate coral bleaching, either independently or under thermal stress from climate change. Rather, the relationship between HPD and temperature stress appears weakly antagonistic for coral bleaching, contradicting the expectation that HPD increases sensitivity of corals to bleaching under thermal stress.Main conclusionsLocal HPD does not interact with global warming for degrading coral reefs. However, regional variation in bleaching patterns exists. Consequently, bleaching will continue to occur on most coral reefs globally regardless of local HPD. Thus, it is likely that even isolated, well‐protected, coral reefs will continue to decline because of climate warming‐induced bleaching. Therefore, tackling the source of global warming remains the most effective way to mitigate coral reef decline via coral bleaching.

Feeding and thermal conditioning enhance coral temperature tolerance in juvenile Pocillopora acuta.

Scleractinian corals form the foundation of coral reefs by acquiring autotrophic nutrition from photosynthetic endosymbionts (Symbiodiniaceae) and use feeding to obtain additional nutrition, especially when the symbiosis is compromised (i.e. bleaching). Juvenile corals are vulnerable to stress due to low energetic reserves and high demand for growth, which is compounded when additional stressors occur. Therefore, conditions that favour energy acquisition and storage may enhance survival under stressful conditions. To investigate the influence of feeding on thermal tolerance, we exposed Pocillopora acuta juveniles to temperature (ambient, 27.4°C versus cool, 25.9°C) and feeding treatments (fed versus unfed) for 30 days post-settlement and monitored growth and physiology, followed by tracking survival under thermal stress. Feeding increased growth and resulted in thicker tissues and elevated symbiont fluorescence. Under high-temperature stress (31–60 days post-settlement; ca 30.1°C), corals that were fed and previously exposed to cool temperature had 33% higher survival than other treatment groups. These corals demonstrated reduced symbiont fluorescence, which may have provided protective effects under thermal stress. These results highlight that the impacts of feeding on coral physiology and stress tolerance are dependent on temperature and as oceans continue to warm, early life stages may experience shifts in feeding strategies to survive.

Correlation between the carbon isotopic composition of planktonic foraminifera-bound organic matter and surface water pCO2 across the equatorial Pacific

For times prior to those represented by the air trapped in Antarctic ice core records, the concentration of CO2 in the atmosphere must be reconstructed using geochemical proxies. The δ13C of particulate organic carbon (POC) produced in ocean surface waters has previously been observed to covary with the concentration of CO2 in the water. Relative to bulk sedimentary organic carbon, the minute quantity of organic matter trapped within the shell walls of planktonic foraminifera, “foraminifera-bound organic matter” (FBOM), has the potential advantage of being protected from diagenetic alteration and contamination by allochthonous organic matter. Here, with new protocols and instrumentation, FBOM-δ13C is investigated as a potential proxy for the aqueous CO2 concentration ([CO2(aq)]) and thus the partial pressure of CO2 (pCO2) in past surface waters. We achieve a full method precision for FBOM-δ13C of 0.4‰ (1SD) on sample sizes of 20 nanomole C by adding a cryofocus step, a helium sheath flow to the oxidation and reduction reactors, and other modifications to an elemental analyzer and by introducing new approaches to reduce contamination during sample preparation. FBOM-δ13C was analyzed in core-top sediments from the eastern tropical Pacific that span the equatorial maximum in surface water [CO2(aq)]. FBOM-δ13C is lower than predicted for marine phytoplankton, consistent with a substantial lipid component in FBOM. Anticorrelation is observed between FBOM-δ13C and climatological [CO2(aq)]; the relationship is statistically significant (P <0.05) in mixed-species samples and in 4 out of 5 picked species. The slope of the FBOM-δ13C:[CO2(aq)] anticorrelation is equivalent to or greater than has been measured for the δ13C of suspended POC in the surface ocean. Based on the few species analyzed in this study, endosymbiont-bearing and -barren species do not clearly differ from each other either in terms of their average value of FBOM-δ13C or the strength of the FBOM-δ13C:[CO2(aq)] anticorrelation, despite the recognized importance of the photosynthetic endosymbionts as a source of organic carbon for the symbiotic species. Correcting for variations in the δ13C of CO2(aq) and phytoplankton growth rate did not improve the significance of the FBOM-δ13C:[CO2(aq)] anticorrelation. The findings support the possibility that FBOM-δ13C can be used as a paleoceanographic proxy for surface water [CO2(aq)] and thus atmospheric pCO2.

In vivo assessment of mitochondrial respiratory alternative oxidase activity and cyclic electron flow around photosystem I on small coral fragments

The mutualistic relationship existing between scleractinian corals and their photosynthetic endosymbionts involves a complex integration of the metabolic pathways within the holobiont. Respiration and photosynthesis are the most important of these processes and although they have been extensively studied, our understanding of their interactions and regulatory mechanisms is still limited. In this work we performed chlorophyll-a fluorescence, oxygen exchange and time-resolved absorption spectroscopy measurements on small and thin fragments (0.3 cm2) of the coral Stylophora pistillata. We showed that the capacity of mitochondrial alternative oxidase accounted for ca. 25% of total coral respiration, and that the high-light dependent oxygen uptake, commonly present in isolated Symbiodiniaceae, was negligible. The ratio between photosystem I (PSI) and photosystem II (PSII) active centers as well as their respective electron transport rates, indicated that PSI cyclic electron flow occurred in high light in S. pistillata and in some branching and lamellar coral species freshly collected in the field. Altogether, these results show the potential of applying advanced biophysical and spectroscopic methods on small coral fragments to understand the complex mechanisms of coral photosynthesis and respiration and their responses to environmental changes.

Conservation help from genomics

Coral Genomics Corals worldwide are under threat from rising sea temperatures and pollution. One response to heat stress is coral bleaching—the loss of photosynthetic endosymbionts that provide energy for the coral. Fuller et al. present a high-resolution genome of the coral Acropora millepora (see the Perspective by Bay and Guerrero). They were able to perform population genetic analyses with samples sequenced at lower coverage and conduct genome-wide association studies. These data were combined to generate a polygenic risk score for bleaching that can be used in coral conservation. Science this issue p. [eaba4674][1]; see also p. [249][2] [1]: /lookup/doi/10.1126/science.aba4674 [2]: /lookup/doi/10.1126/science.abc9342

Population genetics of the coral Acropora millepora: Toward genomic prediction of bleaching.

Although reef-building corals are declining worldwide, responses to bleaching vary within and across species and are partly heritable. Toward predicting bleaching response from genomic data, we generated a chromosome-scale genome assembly for the coral Acropora millepora We obtained whole-genome sequences for 237 phenotyped samples collected at 12 reefs along the Great Barrier Reef, among which we inferred little population structure. Scanning the genome for evidence of local adaptation, we detected signatures of long-term balancing selection in the heat-shock co-chaperone sacsin We conducted a genome-wide association study of visual bleaching score for 213 samples, incorporating the polygenic score derived from it into a predictive model for bleaching in the wild. These results set the stage for genomics-based approaches in conservation strategies.

Diving Into Reef Ecosystems for Land-Agriculture Solutions: Coral Microbiota Can Alleviate Salt Stress During Germination and Photosynthesis in Terrestrial Plants.

From their chemical nature to their ecological interactions, coral reef ecosystems have a lot in common with highly productive terrestrial ecosystems. While plants are responsible for primary production in the terrestrial sphere, the photosynthetic endosymbionts of corals are the key producers in reef communities. As in plants, coral microbiota have been suggested to stimulate the growth and physiological performance of the photosynthetic endosymbionts that provide energy sources to the coral. Among them, actinobacteria are some of the most probable candidates. To explore the potential of coral actinobacteria as plant biostimulants, we have analyzed the activity of Salinispora strains isolated from the corals Porites lobata and Porites panamensis, which were identified as Salinispora arenicola by 16S rRNA sequencing. We evaluated the effects of this microorganism on the germination, plant growth, and photosynthetic response of wild tobacco (Nicotiana attenuata) under a saline regime. We identified protective activity of this actinobacteria on seed germination and photosynthetic performance under natural light conditions. Further insights into the possible mechanism showed an endophytic-like symbiosis between N. attenuata roots and S. arenicola and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity by S. arenicola. We discuss these findings in the context of relevant ecological and physiological responses and biotechnological potential. Overall, our results will contribute to the development of novel biotechnologies to cope with plant growth under saline stress. Our study highlights the importance of understanding marine ecological interactions for the development of novel, strategic, and sustainable agricultural solutions.