Mycosporine-like amino acids from coral dinoflagellates

Unveiling the Anti-Aging Potential of Marine Natural Bioproducts

Aging is a natural process resulting in the progressive impairment of multiple functions in the human body, leading to a decline in cellular functionality and the development of aging-related diseases. External stress factors, such as ultraviolet (UV) radiation, pollution, and toxin exposure, increase oxidative stress, damage cellular repair mechanisms, and speed up aging processes. With the rise in the world's aging population, there are enlarged demands for the use of sustainable natural products in food, nutrient supplements and cosmetics that can slow down aging and prolong healthy life and longevity. Algae, including both macroalgae and microalgae, have been recognised as a source of valuable proteins, amino acids, fatty acids, vitamins, and minerals useful for human consumption and medical applications. With increasing demands for nutraceutical and pharmaceutical bioproducts from environmentally friendly resources, the biotechnological industry, over recent decades, has had to provide new, advanced solutions using modern high-throughput omics technologies. The application of proteomics in the area of discoveries of natural products with anti-aging properties has become more popular for wide industry applications. New proteomics profiling provides a better understanding of changes occurring in protein and peptide content, their structure, function and interactions, as well as the regulatory processes and molecular pathways. Mass spectrometry-based proteomics has been used for a wide range of applications including protein identification, characterisation, as well as quantification of proteins within the proteome and sub-proteome. The application of chemical proteomics facilitated the identification of natural products approach and included the synthesis of probes and target fishing, allowing the advanced identification of proteins of interest. This review focuses on marine macro- and microalgal anti-aging compounds and novel proteomics approaches, providing recent experimental evidence of their involvement in anti-aging processes that should facilitate their use in innovative approaches and sustainable biotechnological applications.

Pharmacological Effects of Antioxidant Mycosporine-Glycine in Alleviating Ultraviolet B-Induced Skin Photodamage: Insights from Metabolomic and Transcriptomic Analyses

Mycosporine-glycine (M-Gly), a member of the mycosporine-like amino acid (MAA) family, is known for its potent antioxidant and anti-inflammatory properties. However, its in vivo efficacy in alleviating acute skin photodamage, primarily caused by oxidative stress, has not been well explored. In this investigation, 30 female ICR mice were divided into four groups: a control group and three Ultraviolet B (UVB)-exposed groups treated with saline or M-Gly via intraperitoneal injection for 30 days. At the end of the experiment, UVB exposure caused erythema, wrinkling, collagen degradation, and mast cell infiltration in mouse dorsal skin. M-Gly treatment improved skin appearance and reduced mast cell numbers, while also elevating antioxidant levels, including superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH). Furthermore, M-Gly reduced inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and IL-1β, typically upregulated after UVB exposure. M-Gly also protected skin collagen by upregulating type I procollagen and decreasing MMP-1 levels. Skin metabolomic profiling identified 34 differentially abundant metabolites, and transcriptomic analysis revealed 752 differentially expressed genes. The combined metabolomic and transcriptomic data indicate that M-Gly's protective effects may involve the regulation of ion transport, cellular repair, metabolic stability, collagen preservation, and the Nrf2/HO-1 pathway. These findings highlight M-Gly's potential as an endogenous antioxidant for protecting skin from UVB-induced damage.

Heat stress in symbiotic dinoflagellates: Implications on oxidative stress and cellular changes

Global warming has been shown to harmfully affect symbiosis between Symbiodiniaceae and other marine invertebrates. When symbiotic dinoflagellates (the genus Breviolum) were in vitro exposed to acute heat stress of +7 °C for a period of 5 days, the results revealed the negative impact on all physiological and other cellular parameters measured. Elevated temperatures resulted in a severe reduction in algal density of up to 9.5-fold, as well as pigment concentrations, indicating the status of the physiological stress and early signs of photo-bleaching. Reactive oxygen species (ROS) were increased in all heated dinoflagellate cells, while the antioxidant-reduced glutathione levels initially dropped on day one but increased under prolonged temperature stress. The cell viability parameters were reduced by 97 % over the heating period, with an increased proportion of apoptotic and necrotic cells. Autofluorescence (AF) for Cy5-PE 660-20 was reduced from 1.7-fold at day 1 to up to 50-fold drop at the end of heating time, indicating that the AF changes were highly sensitive to heat stress and that it could be an extremely sensitive tool for assessing the functionality of algal photosynthetic machinery. The addition of the drug 5-AZA-2'-deoxycytidine (5-AZA), which inhibits DNA methylation processes, was assessed in parallel and contributed to some alterations in algal cellular stress response. The presence of drug 5-AZA combined with the temperature stress had an additional impact on Symbiodiniaceae density and cell complexity, including the AF levels. These variations in cellular stress response under heat stress and compromised DNA methylation conditions may indicate the importance of this epigenetic mechanism for symbiotic dinoflagellate thermal tolerance adaptability over a longer period, which needs further exploration. Consequently, the increased ROS levels and changes in AF signals reported during ongoing heat stress in dinoflagellate cells could be used as early stress biomarkers in these microalgae and potentially other photosynthetic species.

Biofilm-forming bacteria associated with corals secrete melanin with UV-absorption properties

Corals are colonized by a plethora of microorganisms, and their diversity plays a significant role in the health and resilience of corals when they face oxidative stress leading to bleaching. In the current study, we examined 238 bacteria isolated from five different coral species (Acropora hyacinthus, Pocillopora damicornis, Podabacea crustacea, Porites lobata, and Pavona venosa) collected from the coral reef ecosystems of Kavaratti, Lakshadweep Islands, India. We found that bacteria such as Psychrobacter sp., Halomonas sp., Kushneria sp., Staphylococcus sp., Bacillus sp., Brachybacterium sp., Citrobacter sp., and Salinicola sp. were commonly present in the corals. On the other hand, Qipengyuania sp., Faucicola sp., Marihabitans sp., Azomonas sp., Atlantibacter sp., Cedecea sp., Krasalinikoviella sp., and Aidingimonas sp. were not previously reported from the corals. Among the bacterial isolates, a significant number showed high levels of biofilm formation (118), UV absorption (119), and melanin production (127). Considering these properties, we have identified a combination of seven bacteria from the genera Halomonas sp., Psychrobacter sp., Krasalinikoviella sp., and Micrococcus sp. as a potential probiotic consortium for protecting corals from oxidative stress. Overall, this study provides valuable insights into the coral microbiome and opens up possibilities for microbiome-based interventions to protect these crucial ecosystems in the face of global environmental challenges.

Paired metabolomics and volatilomics provides insight into transient high light stress response mechanisms of the coral Montipora mollis

The coral holobiont is underpinned by complex metabolic exchanges between different symbiotic partners, which are impacted by environmental stressors. The chemical diversity of the compounds produced by the holobiont is high and includes primary and secondary metabolites, as well as volatiles. However, metabolites and volatiles have only been characterised in isolation so far. Here, we applied a paired metabolomic-volatilomic approach to characterise holistically the chemical response of the holobiont under stress. Montipora mollis fragments were subjected to high-light stress (8-fold higher than the controls) for 30 min. Photosystem II (PSII) photochemical efficiency values were 7-fold higher in control versus treatment corals immediately following high-light exposure, but returned to pre-stress levels after 30 min of recovery. Under high-light stress, we identified an increase in carbohydrates (> 5-fold increase in arabinose and fructose) and saturated fatty acids (7-fold increase in myristic and oleic acid), together with a decrease in fatty acid derivatives in both metabolites and volatiles (e.g., 80% decrease in oleamide and nonanal), and other antioxidants (~ 85% decrease in sorbitol and galactitol). These changes suggest short-term light stress induces oxidative stress. Correlation analysis between volatiles and metabolites identified positive links between sorbitol, galactitol, six other metabolites and 11 volatiles, with four of these compounds previously identified as antioxidants. This suggests that these 19 compounds may be related and share similar functions. Taken together, our findings demonstrate how paired metabolomics-volatilomics may illuminate broader metabolic shifts occurring under stress and identify linkages between uncharacterised compounds to putatively determine their functions.

Triggers, cascades, and endpoints: connecting the dots of coral bleaching mechanisms

The intracellular coral-dinoflagellate symbiosis is the engine that underpins the success of coral reefs, one of the most diverse ecosystems on the planet. However, the breakdown of the symbiosis and the loss of the microalgal symbiont (i.e. coral bleaching) due to environmental changes are resulting in the rapid degradation of coral reefs globally. There is an urgent need to understand the cellular physiology of coral bleaching at the mechanistic level to help develop solutions to mitigate the coral reef crisis. Here, at an unprecedented scope, we present novel models that integrate putative mechanisms of coral bleaching within a common framework according to the triggers (initiators of bleaching, e.g. heat, cold, light stress, hypoxia, hyposalinity), cascades (cellular pathways, e.g. photoinhibition, unfolded protein response, nitric oxide), and endpoints (mechanisms of symbiont loss, e.g. apoptosis, necrosis, exocytosis/vomocytosis). The models are supported by direct evidence from cnidarian systems, and indirectly through comparative evolutionary analyses from non-cnidarian systems. With this approach, new putative mechanisms have been established within and between cascades initiated by different bleaching triggers. In particular, the models provide new insights into the poorly understood connections between bleaching cascades and endpoints and highlight the role of a new mechanism of symbiont loss, i.e. 'symbiolysosomal digestion', which is different from symbiophagy. This review also increases the approachability of bleaching physiology for specialists and non-specialists by mapping the vast landscape of bleaching mechanisms in an atlas of comprehensible and detailed mechanistic models. We then discuss major knowledge gaps and how future research may improve the understanding of the connections between the diverse cascade of cellular pathways and the mechanisms of symbiont loss (endpoints).

Biotechnological Potential of Macroalgae during Seasonal Blooms for Sustainable Production of UV-Absorbing Compounds

Marine macroalgae (seaweeds) are important primary global producers, with a wide distribution in oceans around the world from polar to tropical regions. Most of these species are exposed to variable environmental conditions, such as abiotic (e.g., light irradiance, temperature variations, nutrient availability, salinity levels) and biotic factors (e.g., grazing and pathogen exposure). As a result, macroalgae developed numerous important strategies to increase their adaptability, including synthesizing secondary metabolites, which have promising biotechnological applications, such as UV-absorbing Mycosporine-Like Amino Acid (MAAs). MAAs are small, water-soluble, UV-absorbing compounds that are commonly found in many marine organisms and are characterized by promising antioxidative, anti-inflammatory and photoprotective properties. However, the widespread use of MAAs by humans is often restricted by their limited bioavailability, limited success in heterologous expression systems, and low quantities recovered from the natural environment. In contrast, bloom-forming macroalgal species from all three major macroalgal clades (Chlorophyta, Phaeophyceae, and Rhodophyta) occasionally form algal blooms, resulting in a rapid increase in algal abundance and high biomass production. This review focuses on the bloom-forming species capable of producing pharmacologically important compounds, including MAAs, and the application of proteomics in facilitating macroalgal use in overcoming current environmental and biotechnological challenges.

Applications of mycosporine-like amino acids beyond photoprotection

Recent years have seen a lot of interest in mycosporine-like amino acids (MAAs) because of their alleged potential as a natural microbial sunscreen. Since chemical ultraviolet (UV) absorbers are unsafe for long-term usage, the demand for natural UV-absorbing substances has increased. In this situation, MAA is a strong contender for an eco-friendly UV protector. The capacity of MAAs to absorb light in the UV-A (320-400 nm) and UV-B (280-320 nm) range without generating free radicals is potentially relevant in photoprotection. The usage of MAAs for purposes other than photoprotection has now shifted in favor of medicinal applications. Aside from UV absorption, MAAs also have anti-oxidant, anti-inflammatory, wound-healing, anti-photoaging, cell proliferation stimulators, anti-cancer agents, and anti-adipogenic properties. Recently, MAAs application to combat SARS-CoV-2 infection was also investigated. In this review article, we highlight the biomedical applications of MAAs that go beyond photoprotection, which can help in utilizing the MAAs as promising bioactive compounds in both pharmaceutical and cosmetic applications.

Recent advancements in coral health, microbiome interactions and climate change

Corals are the visible indicators of the disasters induced by global climate change and anthropogenic activities and have become a highly vulnerable ecosystem on the verge of extinction. Multiple stressors could act individually or synergistically which results in small to large scale tissue degradation, reduced coral covers, and makes the corals vulnerable to various diseases. The coralline diseases are like the Chicken pox in humans because they spread hastily throughout the coral ecosystem and can devastate the coral cover formed over centuries in an abbreviated time. The extinction of the entire reef ecosystem will alter the ocean and earth's amalgam of biogeochemical cycles causing a threat to the entire planet. The current manuscript provides an overview of the recent advancement in coral health, microbiome interactions and climate change. Culture dependent and independent approaches in studying the microbiome of corals, the diseases caused by microorganisms, and the reservoirs of coral pathogens are also discussed. Finally, we discuss the possibilities of protecting the coral reefs from diseases through microbiome transplantation and the capabilities of remote sensing in monitoring their health status.

Exploring Mycosporine-like Amino Acid UV-Absorbing Natural Products for a New Generation of Environmentally Friendly Sunscreens

Human skin needs additional protection from damaging ultraviolet radiation (UVR: 280-400 nm). Harmful UVR exposure leads to DNA damage and the development of skin cancer. Available sunscreens offer chemical protection from detrimental sun radiation to a certain extent. However, many synthetic sunscreens do not provide sufficient UVR protection due to the lack of photostability of their UV-absorbing active ingredients and/or the lack of ability to prevent the formation of free radicals, inevitably leading to skin damage. In addition, synthetic sunscreens may negatively affect human skin, causing irritation, accelerating skin aging and even resulting in allergic reactions. Beyond the potential negative effect on human health, some synthetic sunscreens have been shown to have a harmful impact on the environment. Consequently, identifying photostable, biodegradable, non-toxic, and renewable natural UV filters is imperative to address human health needs and provide a sustainable environmental solution. In nature, marine, freshwater, and terrestrial organisms are protected from harmful UVR through several important photoprotective mechanisms, including the synthesis of UV-absorbing compounds such as mycosporine-like amino acids (MAAs). Beyond MAAs, several other promising, natural UV-absorbing products could be considered for the future development of natural sunscreens. This review investigates the damaging impact of UVR on human health and the necessity of using sunscreens for UV protection, specifically UV-absorbing natural products that are more environmentally friendly than synthetic UV filters. Critical challenges and limitations related to using MAAs in sunscreen formulations are also evaluated. Furthermore, we explain how the genetic diversity of MAA biosynthetic pathways may be linked to their bioactivities and assess MAAs' potential for applications in human health.

The coral microbiome: towards an understanding of the molecular mechanisms of coral-microbiota interactions

Corals live in a complex, multipartite symbiosis with diverse microbes across kingdoms, some of which are implicated in vital functions, such as those related to resilience against climate change. However, knowledge gaps and technical challenges limit our understanding of the nature and functional significance of complex symbiotic relationships within corals. Here, we provide an overview of the complexity of the coral microbiome focusing on taxonomic diversity and functions of well-studied and cryptic microbes. Mining the coral literature indicate that while corals collectively harbour a third of all marine bacterial phyla, known bacterial symbionts and antagonists of corals represent a minute fraction of this diversity and that these taxa cluster into select genera, suggesting selective evolutionary mechanisms enabled these bacteria to gain a niche within the holobiont. Recent advances in coral microbiome research aimed at leveraging microbiome manipulation to increase coral's fitness to help mitigate heat stress-related mortality are discussed. Then, insights into the potential mechanisms through which microbiota can communicate with and modify host responses are examined by describing known recognition patterns, potential microbially derived coral epigenome effector proteins and coral gene regulation. Finally, the power of omics tools used to study corals are highlighted with emphasis on an integrated host-microbiota multiomics framework to understand the underlying mechanisms during symbiosis and climate change-driven dysbiosis.

Genome Mining as an Alternative Way for Screening the Marine Organisms for Their Potential to Produce UV-Absorbing Mycosporine-like Amino Acid

Mycosporine-like amino acids (MAAs) are small molecules with robust ultraviolet (UV)-absorbing capacities and a huge potential to be used as an environmentally friendly natural sunscreen. MAAs, temperature, and light-stable compounds demonstrate powerful photoprotective capacities and the ability to capture light in the UV-A and UV-B ranges without the production of damaging free radicals. The biotechnological uses of these secondary metabolites have been often limited by the small quantities restored from natural resources, variation in MAA expression profiles, and limited success in heterologous expression systems. Overcoming these obstacles requires a better understanding of MAA biosynthesis and its regulatory processes. MAAs are produced to a certain extent via a four-enzyme pathway, including genes encoding enzymes dehydroquinate synthase, enzyme O-methyltransferase, adenosine triphosphate grasp, and a nonribosomal peptide synthetase. However, there are substantial genetic discrepancies in the MAA genetic pathway in different species, suggesting further complexity of this pathway that is yet to be fully explored. In recent years, the application of genome-mining approaches allowed the identification of biosynthetic gene clusters (BGCs) that resulted in the discovery of many new compounds from unconventional sources. This review explores the use of novel genomics tools for linking BGCs and secondary metabolites based on the available omics data, including MAAs, and evaluates the potential of using novel genome-mining tools to reveal a cryptic potential for new bioproduct screening approaches and unrevealing new MAA producers.

Gene clusters for biosynthesis of mycosporine-like amino acids in dinoflagellate nuclear genomes: Possible recent horizontal gene transfer between species of Symbiodiniaceae (Dinophyceae)

Global warming increases the temperature of the ocean surface, which can disrupt dinoflagellate-coral symbioses and result in coral bleaching. Photosynthetic dinoflagellates of the family Symbiodiniaceae include bleaching-tolerant and bleaching-sensitive coral symbionts. Therefore, understanding the molecular mechanisms for changing symbiont diversity is potentially useful to assist recovery of coral holobionts (corals and their associated microbes, including multiple species of Symbiodiniaceae), although sexual reproduction has not been observed in the Symbiodiniaceae. Recent molecular phylogenetic analyses estimate that the Symbiodiniaceae appeared 160 million years ago and diversified into 15 groups, five genera of which now have available draft genomes (i.e., Symbiodinium, Durusdinium, Breviolum, Fugacium, and Cladocopium). Comparative genomic analyses have suggested that crown groups have fewer gene families than early-diverging groups, although many genes that were probably acquired via gene duplications and horizontal gene transfers (HGTs) have been found in each decoded genome. Because UV stress is likely a contributor to coral bleaching, and because the highly conserved gene cluster for mycosporine-like amino acid (MAA) biosynthesis has been found in thermal-tolerant symbiont genomes, I reviewed genomic features of the Symbiodiniaceae, focusing on possible acquisition of a biosynthetic gene cluster for MAAs, which absorb UV radiation. On the basis of highly conserved noncoding sequences, I hypothesized that HGTs have occurred among members of the Symbiodiniaceae and have contributed to the diversification of Symbiodiniaceae-host relationships. Finally, I proposed that bleaching tolerance may be strengthened by multiple MAAs from both symbiotic dinoflagellates and corals.

Advances on marine-derived natural radioprotection compounds: historic development and future perspective

Natural extracts and compounds from marine resources have gained intensive scientific and industry attention for radioprotective activities in the past ten years. However, the marine-derived radioprotectants have been studied against UV-rays, gamma (γ)-rays and X-rays for more than 30 years. This review aims to identify key marine-derived extracts/compounds and their modes of action studied for radioprotective activities from 1986 to 2019. A comprehensive survey was conducted to establish the trend in terms of the publications each year and the countries of origin. A total of 40 extracts and 34 natural compounds showing radioprotective activities against UV-rays, gamma (γ)-rays and X-rays were identified from a range of marine plants and animals. These extracts and compounds are broadly categorized into polysaccharides, phlorotannins, carotenoids and mycosporine-like amino acids (MAAs). Macroalgae and microalgae were found to be the dominant sources of polysaccharides, phlorotannins and carotenoids. MAAs were mainly identified in algae, sponges, sea cucumber and corals that showed significant UV-absorbing activities. A number of radioprotective mechanisms were shown by these compounds, predominantly free radicals scavenging, inhibition of apoptosis, UV-ray absorption and DNA damage-repair signaling pathways. While these bio-discoveries warrant further investigation and development of radioprotective therapeutics, however, the lack of clinical studies is a major obstacle to be tackled in the future.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-021-00095-x.

Recent advances in the discovery of novel marine natural products and mycosporine-like amino acid UV-absorbing compounds

Abstract

Bioactive compounds from marine environments represent a rich source of bioproducts for potential use in medicine and biotechnology. To discover and identify novel marine natural products (MNPs), evaluating diverse biological activities is critical. Increased sensitivity and specificity of omics technologies, especially next-generation high-throughput sequencing combined with liquid chromatography-mass spectrometry and nuclear magnetic resonance, are speeding up the discovery of novel bioactive compounds. Mycosporine-like amino acids (MAAs) isolated from many marine microorganisms are among highly promising MNPs characterized by ultraviolet radiation (UV) absorbing capacities and are recognized as a potential source of ecologically friendly sunscreens. MAAs absorb damaging UV radiation with maximum absorption in the range of 310–360 nm, including both UVA and UVB ranges. MAAs are also characterized by other biological activities such as anti-oxidant, anti-cancer, and anti-inflammatory activities. The application of modern omics approaches promoted some recent developments in our understanding of MAAs’ functional significance and diversity. This review will summarize the various modern tools that could be applied during the identification and characterization of MNPs, including MAAs, to further their innovative applications.

Key points

• New omics technologies are speeding up the discovery of novel bio-products

• The vast diversity of bioactive capacities of marine natural products described

• Marine microorganisms as a source of environmentally friendly sunscreens

From Sea to Skin: Is There a Future for Natural Photoprotectants?

In the last few decades, the thinning of the ozone layer due to increased atmospheric pollution has exacerbated the negative effects of excessive exposure to solar ultraviolet radiation (UVR), and skin cancer has become a major public health concern. In order to prevent skin damage, public health advice mainly focuses on the use of sunscreens, along with wearing protective clothing and avoiding sun exposure during peak hours. Sunscreens present on the market are topical formulations that contain a number of different synthetic, organic, and inorganic UVR filters with different absorbance profiles, which, when combined, provide broad UVR spectrum protection. However, increased evidence suggests that some of these compounds cause subtle damage to marine ecosystems. One alternative may be the use of natural products that are produced in a wide range of marine species and are mainly thought to act as a defense against UVR-mediated damage. However, their potential for human photoprotection is largely under-investigated. In this review, attention has been placed on the molecular strategies adopted by marine organisms to counteract UVR-induced negative effects and we provide a broad portrayal of the recent literature concerning marine-derived natural products having potential as natural sunscreens/photoprotectants for human skin. Their chemical structure, UVR absorption properties, and their pleiotropic role as bioactive molecules are discussed. Most studies strongly suggest that these natural products could be promising for use in biocompatible sunscreens and may represent an alternative eco-friendly approach to protect humans against UV-induced skin damage.

Reproductive plasticity of Hawaiian Montipora corals following thermal stress

Ocean warming, fueled by climate change, is the primary cause of coral bleaching events which are predicted to increase in frequency. Bleaching is generally damaging to coral reproduction, can be exacerbated by concomitant stressors like ultraviolet radiation (UVR), and can have lasting impacts to successful reproduction and potential adaptation. We compared morphological and physiological reproductive metrics (e.g., sperm motility, mitochondrial membrane integrity, egg volume, gametes per bundle, and fertilization and settlement success) of two Hawaiian Montipora corals after consecutive bleaching events in 2014 and 2015. Between the species, sperm motility and mitochondrial membrane potential had the most disparate results. Percent sperm motility in M. capitata, which declined to ~ 40% during bleaching from a normal range of 70-90%, was still less than 50% motile in 2017 and 2018 and had not fully recovered in 2019 (63% motile). By contrast, percent sperm motility in Montipora spp. was 86% and 74% in 2018 and 2019, respectively. This reduction in motility was correlated with damage to mitochondria in M. capitata but not Montipora spp. A major difference between these species is the physiological foundation of their UVR protection, and we hypothesize that UVR protective mechanisms inherent in Montipora spp. mitigate this reproductive damage.

Low levels of ultra-violet radiation mitigate the deleterious effects of nitrate and thermal stress on coral photosynthesis

Reef ecosystems are under increasing pressure from global and local stressors. Rising seawater temperature and high ultraviolet radiation (UVR) levels are the main drivers of the disruption of the coral-dinoflagellate symbiosis (bleaching). Bleaching can also be exacerbated by nitrate contamination in coastal reefs. However, the underlying physiological mechanisms are still poorly understood. Here, we assessed the physiological and oxidative state of the scleractinian coral Pocillopora damicornis, maintained eight weeks in a crossed-factorial design including two temperatures (26 °C or 30 °C), and two nitrate (0.5 and 3 μM-enriched), and UVR (no UVR and 25/1.5 Wm^-2 UVA/B) levels. Nitrate enrichment, and high temperature, significantly impaired coral photosynthesis. However, UVR alleviated the nitrate and temperature-induced decrease in photosynthesis, by increasing the coral's antioxidant capacity. The present study contributes to our understanding of the combined effects of abiotic stressors on coral bleaching susceptibility. Such information is urgently needed to refine reef management strategies.

Mycosporine-Like Amino Acids (MAAs): Biology, Chemistry and Identification Features

Mycosporines and mycosporine-like amino acids are ultra-violet-absorbing compounds produced by several organisms such as lichens, fungi, algae and cyanobacteria, especially upon exposure to solar ultraviolet radiation. These compounds have photoprotective and antioxidant functions. Mycosporine-like amino acids have been used as a natural bioactive ingredient in cosmetic products. Several reviews have already been developed on these photoprotective compounds, but they focus on specific features. Herein, an extremely complete database on mycosporines and mycosporine-like amino acids, covering the whole class of these natural sunscreen compounds known to date, is presented. Currently, this database has 74 compounds and provides information about the chemistry, absorption maxima, protonated mass, fragments and molecular structure of these UV-absorbing compounds as well as their presence in organisms. This platform completes the previous reviews and is available online for free and in the public domain. This database is a useful tool for natural product data mining, dereplication studies, research working in the field of UV-absorbing compounds mycosporines and being integrated in mass spectrometry library software.

Robust natural ultraviolet filters from marine ecosystems for the formulation of environmental friendlier bio-sunscreens

Ultraviolet radiation (UVR) has detrimental effects on human health. It induces oxidative stress, deregulates signaling mechanisms, and produces DNA mutations, factors that ultimately can lead to the development of skin cancer. Therefore, reducing exposure to UVR is of major importance. Among available measures to diminish exposure is the use of sunscreens. However, recent studies indicate that several of the currently used filters have adverse effects on marine ecosystems and human health. This situation leads to the search for new photoprotective compounds that, apart from offering protection, are environmentally friendly. The answer may lie in the same marine ecosystems since molecules such as mycosporine-like amino acids (MAAs) and scytonemin can serve as the defense system of some marine organisms against UVR. This review will discuss the harmful effects of UVR and the mechanisms that microalgae have developed to cope with it. Then it will focus on the biological distribution, characteristics, extraction, and purification methods of MAAs and scytonemin molecules to finally assess its potential as new filters for sunscreen formulation.

Parasitic 'Candidatus Aquarickettsia rohweri' is a marker of disease susceptibility in Acropora cervicornis but is lost during thermal stress

Holobiont phenotype results from a combination of host and symbiont genotypes as well as from prevailing environmental conditions that alter the relationships among symbiotic members. Corals exemplify this concept, where shifts in the algal symbiont community can lead to some corals becoming more or less thermally tolerant. Despite linkage between coral bleaching and disease, the roles of symbiotic bacteria in holobiont resistance and susceptibility to disease remains less well understood. This study thus characterizes the microbiome of disease-resistant and -susceptible Acropora cervicornis coral genotypes (hereafter referred to simply as 'genotypes') before and after high temperature-mediated bleaching. We found that the intracellular bacterial parasite 'Ca. Aquarickettsia rohweri' was strikingly abundant in disease-susceptible genotypes. Disease-resistant genotypes, however, had notably more diverse and even communities, with correspondingly low abundances of 'Ca. Aquarickettsia'. Bleaching caused a dramatic reduction of 'Ca. Aquarickettsia' within disease-susceptible corals and led to an increase in bacterial community dispersion, as well as the proliferation of opportunists. Our data support the hypothesis that 'Ca. Aquarickettsia' species increase coral disease risk through two mechanisms: (i) the creation of host nutritional deficiencies leading to a compromised host-symbiont state and (ii) the opening of niche space for potential pathogens during thermal stress.

Chemotaxonomic Profiling Through NMR1

A metabolite screening of cyanobacteria was performed by nuclear magnetic resonance (NMR) analysis of the soluble material obtained through sequential extraction of the biomass with three different extractive ability solvents (hexane, ethyl acetate, and methanol). Twenty-five strains from the Coimbra Collection of Algae (ACOI) belonging to different orders in the botanical code that represent three subsections of the Stainer-Rippka classification were used. The ¹ H NMR spectra of hexane extracts showed that only two strains of Nostoc genus accumulated triacylglycerols. Monogalactosyldiacylglycerols and digalactosyldiacylglycerols were the major components of the ethyl acetate extracts in a mono- to digalactosyldiacylglycerols ratio of 4.5 estimated by integration of the signals at δ 3.99 and 3.94 ppm (sn3 glycerol methylene). Oligosaccharides of sucrose and mycosporine-like amino acids, among other polar metabolites, were detected in the methanolic extracts. Strains of Nostocales order contained heterocyst glycolipids, whereas sulphoquinovosyldiacylglycerols were absent in one of the studied strains (Microchaete tenera ACOI 1451). Phosphathidylglycerol was identified as the major phospholipid in the methanolic extracts together with minor amounts of phosphatidylcholine based on ¹ H, ³¹ P 2D correlation experiments. Chemotaxonomic information could be easily obtained through the analysis of the δ 3.0-0.5 ppm (fatty acid distribution) and δ 1.2-1.1 ppm (terminal methyl groups of the aglycons in heterocyst glycolipids) regions of the ¹ H NMR spectra of the ethyl acetate and methanol extracts, respectively.

Mycosporine-Like Amino Acids (MAAs) in Zooplankton

Organisms have different adaptations to avoid damage from ultraviolet radiation and one such adaptation is the accumulation of mycosporine-like amino acids (MAAs). These compounds are common in aquatic taxa but a comprehensive review is lacking on their distribution and function in zooplankton. This paper shows that zooplankton MAA concentrations range from non-detectable to ~13 µg mgDW⁻¹. Copepods, rotifers, and krill display a large range of concentrations, whereas cladocerans generally do not contain MAAs. The proposed mechanisms to gain MAAs are via ingestion of MAA-rich food or via symbiotic bacteria providing zooplankton with MAAs. Exposure to UV-radiation increases the concentrations in zooplankton both via increasing MAA concentrations in the phytoplankton food and due to active accumulation. Concentrations are generally low during winter and higher in summer and females seem to deposit MAAs in their eggs. The concentrations of MAAs in zooplankton tend to increase with altitude but only up to a certain altitude suggesting some limitation for the uptake. Shallow and UV-transparent systems tend to have copepods with higher concentrations of MAAs but this has only been shown in a few species. A high MAA concentration has also been shown to lead to lower UV-induced mortality and an overall increased fitness. While there is a lot of information on MAAs in zooplankton we still lack understanding of the potential costs and constraints for accumulation. There is also scarce information in some taxa such as rotifers as well as from systems in tropical, sub(polar) areas as well as in marine systems in general.

Mycosporine-Like Amino Acids: Making the Foundation for Organic Personalised Sunscreens

The surface of the Earth is exposed to harmful ultraviolet radiation (UVR: 280-400 nm). Prolonged skin exposure to UVR results in DNA damage through oxidative stress due to the production of reactive oxygen species (ROS). Mycosporine-like amino acids (MAAs) are UV-absorbing compounds, found in many marine and freshwater organisms that have been of interest in use for skin protection. MAAs are involved in photoprotection from damaging UVR thanks to their ability to absorb light in both the UV-A (315-400 nm) and UV-B (280-315 nm) range without producing free radicals. In addition, by scavenging ROS, MAAs play an antioxidant role and suppress singlet oxygen-induced damage. Currently, there are over 30 different MAAs found in nature and they are characterised by different antioxidative and UV-absorbing capacities. Depending on the environmental conditions and UV level, up- or downregulation of genes from the MAA biosynthetic pathway results in seasonal fluctuation of the MAA content in aquatic species. This review will provide a summary of the MAA antioxidative and UV-absorbing features, including the genes involved in the MAA biosynthesis. Specifically, regulatory mechanisms involved in MAAs pathways will be evaluated for controlled MAA synthesis, advancing the potential use of MAAs in human skin protection.

Utilization of different dissolved organic phosphorus sources by Symbiodinium voratum in vitro

This study examines the physiological responses of the Symbiodiniumvoratum (clade E) to two types of phosphates having different chemical bonds-phosphoesters (C-O-P bonds) and phosphonates (C-P bonds) to explore Symbiodinium cell growth and the molecular perspective of the P utilization process. Alkaline phosphatase (AP), PhnX, PhoA and PhoX expression was profiled for different P conditions using the RT-qPCR method. In a sterile system, Symbiodinium could decompose phosphoesters, such as ATP and glucose 6-phosphate (G-6-P), into dissolved inorganic P (DIP) to supplement inorganic phosphorus but could not directly use phosphoesters for growth. The growth rate and photosynthetic efficiency of zooxanthellae in phosphoester-containing media did not significantly differ from those in the DIP group but were significantly inhibited in medium containing phosphonates such as N-(phosphonomethyl)glycine (glyphosate) and 2-aminoethylphosphonic acid (2-AEP), as well as in DIP-poor medium. The phosphonate group DIP concentration did not change remarkably, indicating that phosphonates can neither be directly used by zooxanthellae nor decomposed into DIP. Our RT-qPCR results support our views that the phosphoesters (C-O-P) had been hydrolyzed outside the cell before being absorbed into the Symbiodinium cell, and implies that PhnX, PhoA and PhoX are perhaps responsible for transporting DIP from medium into cells and for storage of DIP.

Antioxidative, Anti-Inflammatory, and Anti-Aging Properties of Mycosporine-Like Amino Acids: Molecular and Cellular Mechanisms in the Protection of Skin-Aging

Prolonged exposure to ultraviolet (UV) radiation causes photoaging of the skin and induces a number of disorders, including sunburn, fine and coarse wrinkles, and skin cancer risk. Therefore, the application of sunscreen has gained much attention to reduce the harmful effects of UV irradiation on our skin. Recently, there has been a growing demand for the replacement of chemical sunscreens with natural UV-absorbing compounds. Mycosporine-like amino acids (MAAs), promising alternative natural UV-absorbing compounds, are a group of widely distributed, low molecular-weight, water-soluble molecules that can absorb UV radiation and disperse the absorbed energy as heat, without generating reactive oxygen species (ROS). More than 30 MAAs have been characterized, from a variety of organisms. In addition to their UV-absorbing properties, there is substantial evidence that MAAs have the potential to protect against skin aging, including antioxidative activity, anti-inflammatory activity, inhibition of protein-glycation, and inhibition of collagenase activity. This review will provide an overview of MAAs, as potential anti-aging ingredients, beginning with their structure, before moving on to discuss the most recent experimental observations, including the molecular and cellular mechanisms through which MAAs might protect the skin. In particular, we focus on the potential anti-aging activity of mycosporine-2-glycine (M2G).

Adapting to extreme environments: can coral reefs adapt to climate change?

Reef-building corals throughout the world have an annual value of tens of billions of dollars, yet they are being degraded at an increasing rate by many anthropogenic and environmental factors. Despite this, some reefs show resilience to such extreme environmental changes. This review shows how techniques in computational modelling, genetics, and transcriptomics are being used to unravel the complexity of coral reef ecosystems, to try and understand if they can adapt to new and extreme environments. Considering the ambitious climate targets of the Paris Agreement to limit global warming to 2°C, with aspirations of even 1.5°C, questions arise on how to achieve this. Geoengineering may be necessary if other avenues fail, although global governance issues need to play a key role. Development of large and effective coral refugia and marine protected areas is necessary if we are not to lose this vital resource for us all.

2-Ethoxycarbonyl-2-β-hydroxy-a-nor-cholest-5-ene-4one: Extraction, structural characterization, antimicrobial, antioxidant, anticancer and acute toxicity studies

Identification and characterization of marine natural products with antimicrobial, antioxidant activity with minimal toxicity has received much interest over the past few years. Among, Acropora formosa is one of the unexplored marine organism for the screening of natural products in marine resources. In this study, a novel steroid 2-ethoxycarbonyl-2-β-hydroxy-A-nor-cholest-5-ene-4one (ECHC) was isolated from butanol extracts of A. formosa using vacuum liquid chromatography and sequentially purified by column chromatography. The chemical structure of the compound was elucidated based on spectroscopic analysis including GC-MS, ¹H NMR and ¹³C NMR and identified as ECHC. Moreover, in vitro antioxidant activity showed that ECHC was highly scavenged the oxidative stress generative molecules. The in vitro cytotoxic activity of ECHC showed excellent activity against human breast cancer cells. Further, in vivo acute toxicity of ECHC on zebrafish Danio rerio was showed no toxicity as well as no morphological damage was observed after 21 days exposure. Histological analysis revealed that there is no apparent difference was observed between ECHC exposure and control group of D. rerio. Together, these results confirmed that ECHC has in vitro antioxidant and anticancer activity and could be developed as a potential drug against most contagious disease like cancer.

Transcriptomic changes with increasing algal symbiont reveal the detailed process underlying establishment of coral-algal symbiosis

To clarify the establishment process of coral-algal symbiotic relationships, coral transcriptome changes during increasing algal symbiont densities were examined in juvenile corals following inoculation with the algae Symbiodinium goreaui (clade C) and S. trenchii (clade D), and comparison of their transcriptomes with aposymbiotic corals by RNA-sequencing. Since Symbiodinium clades C and D showed very different rates of density increase, comparisons were made of early onsets of both symbionts, revealing that the host behaved differently for each. RNA-sequencing showed that the number of differentially-expressed genes in corals colonized by clade D increased ca. two-fold from 10 to 20 days, whereas corals with clade C showed unremarkable changes consistent with a slow rate of density increase. The data revealed dynamic metabolic changes in symbiotic corals. In addition, the endocytosis pathway was also upregulated, while lysosomal digestive enzymes and the immune system tended to be downregulated as the density of clade D algae increased. The present dataset provides an enormous number of candidate symbiosis-related molecules that exhibit the detailed process by which coral-algal endosymbiosis is established.

Symbiodinium genomes reveal adaptive evolution of functions related to coral-dinoflagellate symbiosis

Symbiosis between dinoflagellates of the genus Symbiodinium and reef-building corals forms the trophic foundation of the world’s coral reef ecosystems. Here we present the first draft genome of Symbiodinium goreaui (Clade C, type C1: 1.03 Gbp), one of the most ubiquitous endosymbionts associated with corals, and an improved draft genome of Symbiodinium kawagutii (Clade F, strain CS-156: 1.05 Gbp) to further elucidate genomic signatures of this symbiosis. Comparative analysis of four available Symbiodinium genomes against other dinoflagellate genomes led to the identification of 2460 nuclear gene families (containing 5% of Symbiodinium genes) that show evidence of positive selection, including genes involved in photosynthesis, transmembrane ion transport, synthesis and modification of amino acids and glycoproteins, and stress response. Further, we identify extensive sets of genes for meiosis and response to light stress. These draft genomes provide a foundational resource for advancing our understanding of Symbiodinium biology and the coral-algal symbiosis.

Huanle Liu et al. report draft genomes of two Symbiodinium species, one from the most dominant type of symbionts in reef-building corals. They find evidence of positive selection in genes related to stress response, meiosis and other traits required for forming successful symbiotic relationships.

The sedoheptulose 7-phosphate cyclases and their emerging roles in biology and ecology

Covering up to: 1999-2016This highlight covers a family of enzymes of growing importance, the sedoheptulose 7-phosphate cyclases, initially of interest due to their involvement in the biosynthesis of pharmaceutically relevant secondary metabolites. More recently, these enzymes have been found throughout Prokarya and Eukarya, suggesting their broad potential biological roles in nature.

Ultraviolet absorbing compounds provide a rapid response mechanism for UV protection in some reef fish

The external mucus surface of reef fish contains ultraviolet absorbing compounds (UVAC), most prominently Mycosporine-like Amino Acids (MAAs). MAAs in the external mucus of reef fish are thought to act as sunscreens by preventing the damaging effects of ultraviolet radiation (UVR), however, direct evidence for their protective role has been missing. We tested the protective function of UVAC's by exposing fish with naturally low, Pomacentrus amboinensis, and high, Thalassoma lunare, mucus absorption properties to a high dose of UVR (UVB: 13.4W∗m(-2), UVA: 6.1W∗m(-2)) and measuring the resulting DNA damage in the form of cyclobutane pyrimidine dimers (CPDs). For both species, the amount of UV induced DNA damage sustained following the exposure to a 1h pulse of high UVR was negatively correlated with mucus absorbance, a proxy for MAA concentration. Furthermore, a rapid and significant increase in UVAC concentration was observed in P. amboinensis following UV exposure, directly after capture and after ten days in captivity. No such increase was observed in T. lunare, which maintained relatively high levels of UV absorbance at all times. P. amboinensis, in contrast to T. lunare, uses UV communication and thus must maintain UV transparent mucus to be able to display its UV patterns. The ability to rapidly alter the transparency of mucus could be an important adaptation in the trade off between protection from harmful UVR and UV communication.

Extraction and Analysis of Mycosporine-Like Amino Acids in Marine Algae

Marine organisms use mycosporine-like amino acids (MAAs) as biological sunscreens for the protection from damaging ultraviolet (UV) radiation and the prevention of oxidative stress. MAAs have been discovered in many different marine and freshwater species including cyanobacteria, fungi, and algae, but also in animals like cnidarian and fishes. Here, we describe a general method for the isolation and characterization of MAA compounds from red algae and symbiotic dinoflagellates isolated from coral hosts. This method is also suitable for the extraction and analyses of MAAs from a range of other algal and marine biota.

Sunscreens of red algae from Patagonia: a biotechnological perspective

Red algae can synthesize UV-absorbing mycosporine-like amino acid (MAA) compounds to minimize the damage caused by UV radiation. MAAs are molecules with low molecular weight and absorption maxima in the UV region (310–360 nm). Combined with their antioxidant activities, these features suggest a potential application in the prevention and therapeutic treatment of afflictions related to free-radical production and UV irradiation in humans. However, the use of MAAs in biotechnological products is limited by the low concentrations of these compounds in macroalgae harvested from the wild. Thus, species with high MAA concentrations are desirable. Information on red algae from Patagonia generally shows low concentrations of MAAs. However, increased MAA or at least changes in individual MAA concentration have been observed in certain species under stressful conditions. Additionally, methanolic extracts show an interesting absorption in the UVB region in certain red algae species, such as Lophurella hoockeriana.

De novo synthesis of a sunscreen compound in vertebrates

Ultraviolet-protective compounds, such as mycosporine-like amino acids (MAAs) and related gadusols produced by some bacteria, fungi, algae, and marine invertebrates, are critical for the survival of reef-building corals and other marine organisms exposed to high-solar irradiance. These compounds have also been found in marine fish, where their accumulation is thought to be of dietary or symbiont origin. In this study, we report the unexpected discovery that fish can synthesize gadusol de novo and that the analogous pathways are also present in amphibians, reptiles, and birds. Furthermore, we demonstrate that engineered yeast containing the fish genes can produce and secrete gadusol. The discovery of the gadusol pathway in vertebrates provides a platform for understanding its role in these animals, and the possibility of engineering yeast to efficiently produce a natural sunscreen and antioxidant presents an avenue for its large-scale production for possible use in pharmaceuticals and cosmetics.

DOI:http://dx.doi.org/10.7554/eLife.05919.001

Sunlight is the Earth's primary energy source and is exploited by an array of natural and man-made processes. Photosynthetic plants harness solar energy to convert carbon dioxide and water into biomass, and solar panels capture light and convert it to electricity. Sunlight is critical to life on Earth, and yet excessive exposure to sunlight can cause serious harm as it contains ultraviolet (UV) radiation, which damages the DNA of cells. In humans, this damage can lead to conditions such as cataracts and skin cancer.

The marine organisms and animals that live in the upper ocean and on reefs are subject to intense and unrelenting sunlight. In their effort to protect against potentially deadly UV radiation, many small and particularly vulnerable marine organisms, such as bacteria and algae, produce UV-protective sunscreens. While UV-protective compounds have also been found in larger organisms, including fish and their eggs, the presence of these sunscreens has always been attributed to the animal sequestering the compounds from their environment or partnering with a sunscreen-producing microorganism.

Now, Osborn, Almabruk, Holzwarth et al. have discovered a fish that is able to produce such a UV-protective compound completely on its own. After identifying the full set of genes—or pathway—responsible for generating the UV-protective compound, the same pathway was detected in a variety of diverse animals, including amphibians, reptiles, and birds. This opens up a new area of study, because besides providing UV protection, no one yet knows what other roles the molecule may have in these animals. Furthermore, introducing the complete pathway into yeast enabled these cells to produce the sunscreen. In the future, engineering a yeast population to produce large quantities of the natural sunscreen could lead to large-scale production of the UV-protective compound so it can be used in pharmaceuticals and cosmetics.

DOI:http://dx.doi.org/10.7554/eLife.05919.002

Contrasting patterns of MAAs accumulation in two populations of the copepod Boeckella gracilipes

The bio-accumulation of mycosporine-like amino acids (MAAs) is common in planktonic copepods that inhabit environments exposed to high levels of solar radiation. MAAs accumulation in copepods can be affected both by extrinsic (environmental) and intrinsic factors (local adaptation, genotype, etc.). Laboratory experiments were performed to study the bio-accumulation of MAAs in two geographically-isolated populations of Boeckella gracilipes from a mountain and a piedmont lake of North Patagonia. We performed two series of 10-day incubations of B. gracilipes from the different lakes applying two radiation conditions (PAR + UVR and darkness), at five different temperatures (5 to 20 °C) and providing a MAA-free flagellate as food. We assumed that differences in final MAAs concentrations between copepod populations should be exclusively due to environmental factors, and that any difference in the patterns of MAAs accumulation should exclusively arise from differences in MAAs concentration at the time of collection. MAAs concentration was three fold higher in B. gracilipes from Lake Verde than in copepods from the Lake Morenito. The MAAs suite was dominated (∼90%) by a combination of porphyra-334 and mycosporine-glycine in copepods from Lake Verde, and porphyra-334 and MAA-332 in those from Lake Morenito. Two exclusive MAA compounds were identified, mycosporine-glycine in copepods from Lake Verde and shinorine in the copepod population from Lake Morenito. Laboratory experiments showed that: (i) exposure to PAR + UVR stimulated the accumulation of MAAs in both copepod populations; (ii) temperature affected the response of MAAs and, remarkably, low temperatures stimulated MAAs accumulation even in dark incubations, (iii) the response to radiation and temperature in MAAs accumulation was more pronounced in the population with low initial MAAs than in the population with high initial MAAs concentrations. The differences in intrinsic factors between B. gracilipes populations, such as local adaptation to contrasting UV and temperature scenarios, among others, appear to play an important role in determining levels and patterns of MAAs accumulation in B. gracilipes.

New-old hemoglobin-like proteins of symbiotic dinoflagellates

Symbiotic dinoflagellates are unicellular photosynthetic algae that live in mutualistic symbioses with many marine organisms. Within the transcriptome of coral endosymbionts Symbiodinium sp. (type C3), we discovered the sequences of two novel and highly polymorphic hemoglobin-like genes and proposed their 3D protein structures. At the protein level, four isoforms shared between 87 and 97% sequence identity for Hb-1 and 78-99% for Hb-2, whereas between Hb-1 and Hb-2 proteins, only 15-21% sequence homology has been preserved. Phylogenetic analyses of the dinoflagellate encoding Hb sequences have revealed a separate evolutionary origin of the discovered globin genes and indicated the possibility of horizontal gene transfer. Transcriptional regulation of the Hb-like genes was studied in the reef-building coral Acropora aspera exposed to elevated temperatures (6-7°C above average sea temperature) over a 24-h period and a 72-h period, as well as to nutrient stress. Exposure to elevated temperatures resulted in an increased Hb-1 gene expression of 31% after 72 h only, whereas transcript abundance of the Hb-2 gene was enhanced by up to 59% by both 1-day and 3-day thermal stress conditions. Nutrient stress also increased gene expression of Hb-2 gene by 70%. Our findings describe the differential expression patterns of two novel Hb genes from symbiotic dinoflagellates and their polymorphic nature. Furthermore, the inducible nature of Hb-2 gene by both thermal and nutrient stressors indicates a prospective role of this form of hemoglobin in the initial coral-algal responses to changes in environmental conditions. This novel hemoglobin has potential use as a stress biomarker.

Phylogenetic analysis of genes involved in mycosporine-like amino acid biosynthesis in symbiotic dinoflagellates

Mycosporine-like amino acids (MAAs) are multifunctional secondary metabolites involved in photoprotection in many marine organisms. As well as having broad ultraviolet (UV) absorption spectra (310-362 nm), these biological sunscreens are also involved in the prevention of oxidative stress. More than 20 different MAAs have been discovered so far, characterized by distinctive chemical structures and a broad ecological distribution. Additionally, UV-screening MAA metabolites have been investigated and used in biotechnology and cosmetics. The biosynthesis of MAAs has been suggested to occur via either the shikimate or pentose phosphate pathways. Despite their wide distribution in marine and freshwater species and also the commercial application in cosmetic products, there are still a number of uncertainties regarding the genetic, biochemical, and evolutionary origin of MAAs. Here, using a transcriptome-mining approach, we identify the gene counterparts from the shikimate or pentose phosphate pathway involved in MAA biosynthesis within the sequences of the reef-building coral symbiotic dinoflagellates (genus Symbiodinium). We also report the highly similar sequences of genes from the proposed MAA biosynthetic pathway involved in the metabolism of 4-deoxygadusol (direct MAA precursor) in various Symbiodinium strains confirming their algal origin and conserved nature. Finally, we reveal the separate identity of two O-methyltransferase genes, possibly involved in MAA biosynthesis, as well as nonribosomal peptide synthetase and adenosine triphosphate grasp homologs in symbiotic dinoflagellates. This study provides a biochemical and phylogenetic overview of the genes from the proposed MAA biosynthetic pathway with a focus on coral endosymbionts.