Genome Improvement and Core Gene Set Refinement of Fugacium kawagutii

Protocol for mapping the three-dimensional organization of dinoflagellate genomes

Dinoflagellate genomes often are very large and difficult to assemble, which has until recently precluded their analysis with modern functional genomic tools. Here, we present a protocol for mapping three-dimensional (3D) genome organization in dinoflagellates and using it for scaffolding their genome assemblies. We describe steps for crosslinking, nuclear lysis, denaturation, restriction digest, ligation, and DNA shearing and purification. We then detail procedures sequencing library generation and computational analysis, including initial Hi-C read mapping and 3D-DNA scaffolding/assembly correction. For complete details on the use and execution of this protocol, please refer to Marinov et al.1.

Massive genome reduction predates the divergence of Symbiodiniaceae dinoflagellates

Dinoflagellates in the family Symbiodiniaceae are taxonomically diverse, predominantly symbiotic lineages that are well-known for their association with corals. The ancestor of these taxa is believed to have been free-living. The establishment of symbiosis (i.e. symbiogenesis) is hypothesized to have occurred multiple times during Symbiodiniaceae evolution, but its impact on genome evolution of these taxa is largely unknown. Among Symbiodiniaceae, the genus Effrenium is a free-living lineage that is phylogenetically positioned between two robustly supported groups of genera within which symbiotic taxa have emerged. The apparent lack of symbiogenesis in Effrenium suggests that the ancestral features of Symbiodiniaceae may have been retained in this lineage. Here, we present de novo assembled genomes (1.2-1.9 Gbp in size) and transcriptome data from three isolates of Effrenium voratum and conduct a comparative analysis that includes 16 Symbiodiniaceae taxa and the other dinoflagellates. Surprisingly, we find that genome reduction, which is often associated with a symbiotic lifestyle, predates the origin of Symbiodiniaceae. The free-living lifestyle distinguishes Effrenium from symbiotic Symbiodiniaceae vis-à-vis their longer introns, more-extensive mRNA editing, fewer (~30%) lineage-specific gene sets, and lower (~10%) level of pseudogenization. These results demonstrate how genome reduction and the adaptation to distinct lifestyles intersect to drive diversification and genome evolution of Symbiodiniaceae.

Developing model systems for dinoflagellates in the post-genomic era

Dinoflagellates are a diverse group of eukaryotic microbes that are ubiquitous in aquatic environments. Largely photosynthetic, they encompass symbiotic, parasitic, and free-living lineages with a broad spectrum of trophism. Many free-living taxa can produce bioactive secondary metabolites such as biotoxins, some of which cause harmful algal blooms. In contrast, most symbiotic species are crucial for sustaining coral reef health. The year 2023 marked a decade since the first genome data of dinoflagellates became available. The growing genome-scale resources for these taxa are highlighting their remarkable evolutionary and genomic complexities. Here, we discuss the prospect of developing dinoflagellate models using the criteria of accessibility, tractability, resources, research support, and promise. Moving forward in the post-genomic era, we argue for the development of fit-to-purpose models that tailor to specific biological contexts, and that a one-size-fits-all model is inadequate for encapsulating the complex biology, ecology, and evolutionary history of dinoflagellates.

Ribosome profiling in the Symbiodiniacean dinoflagellate Fugacium kawagutii shows coordinated protein synthesis of enzymes in different pathways at different times of day

Dinoflagellates respond to daily changes in light and dark by changes in cellular metabolism, yet the mechanisms used are still unclear. For example, Fugacium (previously Symbiodinium) kawagutii shows little difference in the transcriptome between day and night suggesting little transcriptional control over gene expression. Here, we have performed ribosome profiling at 2 h intervals over a daily light-dark cycle to assess the degree to which protein synthesis rates might change over the daily cycle. The number of F. kawagutii coding sequences with significant differences in the number of ribosome-protected fragments (RPF) over the 24-h cycle was 2923 using JTK_Cycle and 3655 using ECHO. The majority of the regulated transcripts showed peak translation at the onset of the dark period. The regulated sequences were assigned to different KEGG pathways and transcripts that were translated at roughly the same time were termed concurrently regulated. Both analyses revealed concurrent regulation of many transcripts whose gene products were involved in spliceosome or lysosome biogenesis with peak translation rates around the onset of the dark period, while others, involved in nitrate metabolism and ribosomal proteins, were preferentially translated around the onset of the day phase or the end of the night phase, respectively. In addition, some sequences involved in DNA synthesis were preferentially translated at the end of the day. We conclude that light-dark cycles seem able to synchronize translation of some transcripts encoding proteins involved in a range of different cellular processes, and propose that these changes may help the cells adapt and alter their metabolism as a function of the time of day.

Genomic conservation and putative downstream functionality of the phosphatidylinositol signalling pathway in the cnidarian-dinoflagellate symbiosis

The mutualistic cnidarian-dinoflagellate symbiosis underpins the evolutionary success of stony corals and the persistence of coral reefs. However, a molecular understanding of the signalling events that lead to the successful establishment and maintenance of this symbiosis remains unresolved. For example, the phosphatidylinositol (PI) signalling pathway has been implicated during the establishment of multiple mutualistic and parasitic interactions across the kingdoms of life, yet its role within the cnidarian-dinoflagellate symbiosis remains unexplored. Here, we aimed to confirm the presence and assess the specific enzymatic composition of the PI signalling pathway across cnidaria and dinoflagellates by compiling 21 symbiotic anthozoan (corals and sea anemones) and 28 symbiotic dinoflagellate (Symbiodiniaceae) transcriptomic and genomic datasets and querying genes related to this pathway. Presence or absence of PI-kinase and PI-phosphatase orthologs were also compared between a broad sampling of taxonomically related symbiotic and non-symbiotic species. Across the symbiotic anthozoans analysed, there was a complete and highly conserved PI pathway, analogous to the pathway found in model eukaryotes. The Symbiodiniaceae pathway showed similarities to its sister taxon, the Apicomplexa, with the absence of PI 4-phosphatases. However, conversely to Apicomplexa, there was also an expansion of homologs present in the PI5-phosphatase and PI5-kinase groups, with unique Symbiodiniaceae proteins identified that are unknown from non-symbiotic unicellular organisms. Additionally, we aimed to unravel the putative functionalities of the PI signalling pathway in this symbiosis by analysing phosphoinositide (PIP)-binding proteins. Analysis of phosphoinositide (PIP)-binding proteins showed that, on average, 2.23 and 1.29% of the total assemblies of anthozoan and Symbiodiniaceae, respectively, have the potential to bind to PIPs. Enrichment of Gene Ontology (GO) terms associated with predicted PIP-binding proteins within each taxon revealed a broad range of functions, including compelling links to processes putatively involved in symbiosis regulation. This analysis establishes a baseline for current understanding of the PI pathway across anthozoans and Symbiodiniaceae, and thus a framework to target future research.

Building consensus around the assessment and interpretation of Symbiodiniaceae diversity

Within microeukaryotes, genetic variation and functional variation sometimes accumulate more quickly than morphological differences. To understand the evolutionary history and ecology of such lineages, it is key to examine diversity at multiple levels of organization. In the dinoflagellate family Symbiodiniaceae, which can form endosymbioses with cnidarians (e.g., corals, octocorals, sea anemones, jellyfish), other marine invertebrates (e.g., sponges, molluscs, flatworms), and protists (e.g., foraminifera), molecular data have been used extensively over the past three decades to describe phenotypes and to make evolutionary and ecological inferences. Despite advances in Symbiodiniaceae genomics, a lack of consensus among researchers with respect to interpreting genetic data has slowed progress in the field and acted as a barrier to reconciling observations. Here, we identify key challenges regarding the assessment and interpretation of Symbiodiniaceae genetic diversity across three levels: species, populations, and communities. We summarize areas of agreement and highlight techniques and approaches that are broadly accepted. In areas where debate remains, we identify unresolved issues and discuss technologies and approaches that can help to fill knowledge gaps related to genetic and phenotypic diversity. We also discuss ways to stimulate progress, in particular by fostering a more inclusive and collaborative research community. We hope that this perspective will inspire and accelerate coral reef science by serving as a resource to those designing experiments, publishing research, and applying for funding related to Symbiodiniaceae and their symbiotic partnerships.

The genome of a hadal sea cucumber reveals novel adaptive strategies to deep-sea environments

How organisms cope with coldness and high pressure in the hadal zone remains poorly understood. Here, we sequenced and assembled the genome of hadal sea cucumber Paelopatides sp. Yap with high quality and explored its potential mechanisms for deep-sea adaptation. First, the expansion of ACOX1 for rate-limiting enzyme in the DHA synthesis pathway, increased DHA content in the phospholipid bilayer, and positive selection of EPT1 may maintain cell membrane fluidity. Second, three genes for translation initiation factors and two for ribosomal proteins underwent expansion, and three ribosomal protein genes were positively selected, which may ameliorate the protein synthesis inhibition or ribosome dissociation in the hadal zone. Third, expansion and positive selection of genes associated with stalled replication fork recovery and DNA repair suggest improvements in DNA protection. This is the first genome sequence of a hadal invertebrate. Our results provide insights into the genetic adaptations used by invertebrate in deep oceans.

High-quality genome assembles from key Hawaiian coral species

Background

Coral reefs house about 25% of marine biodiversity and are critical for the livelihood of many communities by providing food, tourism revenue, and protection from wave surge. These magnificent ecosystems are under existential threat from anthropogenic climate change. Whereas extensive ecological and physiological studies have addressed coral response to environmental stress, high-quality reference genome data are lacking for many of these species. The latter issue hinders efforts to understand the genetic basis of stress resistance and to design informed coral conservation strategies.

Results

We report genome assemblies from 4 key Hawaiian coral species, Montipora capitata, Pocillopora acuta, Pocillopora meandrina, and Porites compressa. These species, or members of these genera, are distributed worldwide and therefore of broad scientific and ecological importance. For M. capitata, an initial assembly was generated from short-read Illumina and long-read PacBio data, which was then scaffolded into 14 putative chromosomes using Omni-C sequencing. For P. acuta, P. meandrina, and P. compressa, high-quality assemblies were generated using short-read Illumina and long-read PacBio data. The P. acuta assembly is from a triploid individual, making it the first reference genome of a nondiploid coral animal.

Conclusions

These assemblies are significant improvements over available data and provide invaluable resources for supporting multiomics studies into coral biology, not just in Hawaiʻi but also in other regions, where related species exist. The P. acuta assembly provides a platform for studying polyploidy in corals and its role in genome evolution and stress adaptation in these organisms.

Improved Cladocopium goreaui Genome Assembly Reveals Features of a Facultative Coral Symbiont and the Complex Evolutionary History of Dinoflagellate Genes

Dinoflagellates of the family Symbiodiniaceae are crucial photosymbionts in corals and other marine organisms. Of these, Cladocopium goreaui is one of the most dominant symbiont species in the Indo-Pacific. Here, we present an improved genome assembly of C. goreaui combining new long-read sequence data with previously generated short-read data. Incorporating new full-length transcripts to guide gene prediction, the C. goreaui genome (1.2 Gb) exhibits a high extent of completeness (82.4% based on BUSCO protein recovery) and better resolution of repetitive sequence regions; 45,322 gene models were predicted, and 327 putative, topologically associated domains of the chromosomes were identified. Comparison with other Symbiodiniaceae genomes revealed a prevalence of repeats and duplicated genes in C. goreaui, and lineage-specific genes indicating functional innovation. Incorporating 2,841,408 protein sequences from 96 taxonomically diverse eukaryotes and representative prokaryotes in a phylogenomic approach, we assessed the evolutionary history of C. goreaui genes. Of the 5246 phylogenetic trees inferred from homologous protein sets containing two or more phyla, 35–36% have putatively originated via horizontal gene transfer (HGT), predominantly (19–23%) via an ancestral Archaeplastida lineage implicated in the endosymbiotic origin of plastids: 10–11% are of green algal origin, including genes encoding photosynthetic functions. Our results demonstrate the utility of long-read sequence data in resolving structural features of a dinoflagellate genome, and highlight how genetic transfer has shaped genome evolution of a facultative symbiont, and more broadly of dinoflagellates.

Energy metabolism and genetic information processing mark major transitions in the life history of Scrippsiella acuminata (Dinophyceae)

Many dinoflagellates perform sexual reproduction and form cysts as a life history strategy to survive adverse environmental conditions and seed annual harmful algal blooms (HABs). The molecular mechanisms underpinning the life stage transitions can provide clues about how key environmental factors induce encystment and initiation of a HAB but are still poorly understood. Here, we conducted an integrated physiological and transcriptomic study to unravel the mechanisms in Scrippsiella acuminata. We established a culture from a bloom, induced cyst formation, and divided the process into four life stages. Transcriptomic analysis of these stages revealed 19,900 differentially expressed genes (DEGs). The expression of genes related to photosynthesis was significantly up-regulated from vegetative stage to immature cyst stage, consistent with the marked increase in cell contents of energy-storing macromolecules (carbohydrates and lipids). When proceeding to resting cysts, most photosynthesis genes were down-regulated while "genetic information processing" related genes were up-regulated. Comparing germinating cysts with resting cysts revealed 100 DEGs involved in energy metabolism, indicating a high energy requirement of germination. In addition, the transition from germinating cysts to vegetative cells featured up-regulation of photosynthesis. Our results demonstrate that energy storage and consumption play a pivotal role in cyst formation and germination respectively and genetic information processing is crucial in cyst dormancy.

An overview of transcription in dinoflagellates

Dinoflagellates are a vital diverse family of unicellular algae widespread in various aquatic environments. Typically large genomes and permanently condensed chromosomes without histones make these organisms unique among eukaryotes in terms of chromatin structure and gene expression. Genomic and transcriptomic sequencing projects have provided new insight into the genetic foundation of dinoflagellate behaviors. Genes in tandem arrays, trans-splicing of mRNAs and lower levels of transcriptional regulation compared to other eukaryotes all contribute to the differences seen. Here we present a general overview of transcription in dinoflagellates based on previously described work.

Alignment-Free Analysis of Whole-Genome Sequences From Symbiodiniaceae Reveals Different Phylogenetic Signals in Distinct Regions

Dinoflagellates of the family Symbiodiniaceae are predominantly essential symbionts of corals and other marine organisms. Recent research reveals extensive genome sequence divergence among Symbiodiniaceae taxa and high phylogenetic diversity hidden behind subtly different cell morphologies. Using an alignment-free phylogenetic approach based on sub-sequences of fixed length k (i.e. k-mers), we assessed the phylogenetic signal among whole-genome sequences from 16 Symbiodiniaceae taxa (including the genera of Symbiodinium, Breviolum, Cladocopium, Durusdinium and Fugacium) and two strains of Polarella glacialis as outgroup. Based on phylogenetic trees inferred from k-mers in distinct genomic regions (i.e. repeat-masked genome sequences, protein-coding sequences, introns and repeats) and in protein sequences, the phylogenetic signal associated with protein-coding DNA and the encoded amino acids is largely consistent with the Symbiodiniaceae phylogeny based on established markers, such as large subunit rRNA. The other genome sequences (introns and repeats) exhibit distinct phylogenetic signals, supporting the expected differential evolutionary pressure acting on these regions. Our analysis of conserved core k-mers revealed the prevalence of conserved k-mers (>95% core 23-mers among all 18 genomes) in annotated repeats and non-genic regions of the genomes. We observed 180 distinct repeat types that are significantly enriched in genomes of the symbiotic versus free-living Symbiodinium taxa, suggesting an enhanced activity of transposable elements linked to the symbiotic lifestyle. We provide evidence that representation of alignment-free phylogenies as dynamic networks enhances the ability to generate new hypotheses about genome evolution in Symbiodiniaceae. These results demonstrate the potential of alignment-free phylogenetic methods as a scalable approach for inferring comprehensive, unbiased whole-genome phylogenies of dinoflagellates and more broadly of microbial eukaryotes.

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.

Spatial organization of dinoflagellate genomes: Novel insights and remaining critical questions

As is true for many other aspects, genome architecture, evolution, and function in dinoflagellates are enigmatic and, in the meantime, continuous inspiration for scientific quests. Recent third-generation sequencing and Hi-C linkage analyses brought new insights into the spatial organization of symbiodiniacean genomes, revealing the topologically associated domains, discrete gene clusters and their cis and trans orientations, and relationships with transcription. Where do these new findings bring us in dinoflagellate genomics? Here, we aim to place these new results in the backdrop of the long history of research on this topic and in the context of what critical questions remain to be pursued in the future. The new data suggest, pending verification of other complete chromosome assemblies, a potential evolutionary trend in chromosome number decrease and length increase within the Symbiodiniaceae. While questions remain about the mechanics of the three-dimensional chromosome structure and cell cycle-related DNA replication, the mechanisms of gene transcription and genome size evolution, these latest findings set new starting points for further inquiries.

Genomic and Experimental Investigations of Auriscalpium and Strobilurus Fungi Reveal New Insights into Pinecone Decomposition

Saprophytic fungi (SPF) play vital roles in ecosystem dynamics and decomposition. However, because of the complexity of living systems, our understanding of how SPF interact with each other to decompose organic matter is very limited. Here we studied their roles and interactions in the decomposition of highly specialized substrates between the two genera Auriscalpium and Strobilurus fungi-colonized fallen pinecones of the same plant sequentially. We obtained the genome sequences from seven fungal species with three pairs: A. orientale-S. luchuensis, A. vulgare-S. stephanocystis and A. microsporum-S. pachcystidiatus/S. orientalis on cones of Pinus yunnanensis, P. sylvestris and P. armandii, respectively, and the organic profiles of substrate during decomposition. Our analyses revealed evidence for both competition and cooperation between the two groups of fungi during decomposition, enabling efficient utilization of substrates with complementary profiles of carbohydrate active enzymes (CAZymes). The Auriscalpium fungi are highly effective at utilizing the primary organic carbon, such as lignin, and hemicellulose in freshly fallen cones, facilitated the invasion and colonization by Strobilurus fungi. The Strobilurus fungi have genes coding for abundant CAZymes to utilize the remaining organic compounds and for producing an arsenal of secondary metabolites such as strobilurins that can inhibit other fungi from colonizing the pinecones.

Assessing nucleic acid binding activity of four dinoflagellate cold shock domain proteins from Symbiodinium kawagutii and Lingulodinium polyedra

Background

Dinoflagellates have a generally large number of genes but only a small percentage of these are annotated as transcription factors. Cold shock domain (CSD) containing proteins (CSPs) account for roughly 60% of these. CSDs are not prevalent in other eukaryotic lineages, perhaps suggesting a lineage-specific expansion of this type of transcription factors in dinoflagellates, but there is little experimental data to support a role for dinoflagellate CSPs as transcription factors. Here we evaluate the hypothesis that dinoflagellate CSPs can act as transcription factors by binding double-stranded DNA in a sequence dependent manner.

Results

We find that both electrophoretic mobility shift assay (EMSA) competition experiments and selection and amplification binding (SAAB) assays indicate binding is not sequence specific for four different CSPs from two dinoflagellate species. Competition experiments indicate all four CSPs bind to RNA better than double-stranded DNA.

Conclusion

Dinoflagellate CSPs do not share the nucleic acid binding properties expected for them to function as bone fide transcription factors. We conclude the transcription factor complement of dinoflagellates is even smaller than previously thought suggesting that dinoflagellates have a reduced dependance on transcriptional control compared to other eukaryotes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12860-021-00368-4.

Physiological and transcriptomic responses to N-deficiency and ammonium: Nitrate shift in Fugacium kawagutii (Symbiodiniaceae)

Symbiodiniaceae are the source of essential coral symbionts of reef building corals. The growth and density of endosymbiotic Symbiodiniaceae within the coral host is dependent on nutrient availability, yet little is known about how Symbiodiniaceae respond to the dynamics of the nutrients, including switch between different chemical forms and changes in abundance. In this study, we investigated physiological, cytometric, and transcriptomic responses in Fugacium kawagutii to nitrogen (N)-nutrient deficiency and different chemical N forms (nitrate and ammonium) in batch culture conditions. We mainly found that ammonium was consumed faster than nitrate when provided separately, and was preferentially utilized over nitrate when both N compounds were supplied at 1:2, 1:1 and 2:1 molarity ratios. Besides, N-deficiency caused decreases in growth, energy production, antioxidative capacity and investment in photosynthate transport but increased energy consumption. Growing on ammonium produced a similar cell yield as nitrate, but with a reduced investment in nutrient transport and assimilation; yet at high concentrations ammonium exhibited inhibitory effects. These findings together have important implications in N-nutrient regulation of coral symbiosis. In addition, we identified ten highly and stably expressed genes as candidate reference genes, which will be potentially useful for gene expression studies in the future.

A New Dinoflagellate Genome Illuminates a Conserved Gene Cluster Involved in Sunscreen Biosynthesis

Photosynthetic dinoflagellates of the Family Symbiodiniaceae live symbiotically with many organisms that inhabit coral reefs and are currently classified into fifteen groups, including seven genera. Draft genomes from four genera, Symbiodinium, Breviolum, Fugacium, and Cladocopium, which have been isolated from corals, have been reported. However, no genome is available from the genus Durusdinium, which occupies an intermediate phylogenetic position in the Family Symbiodiniaceae and is well known for thermal tolerance (resistance to bleaching). We sequenced, assembled, and annotated the genome of Durusdinium trenchii, isolated from the coral, Favia speciosa, in Okinawa, Japan. Assembled short reads amounted to 670 Mb with ∼47% GC content. This GC content was intermediate among taxa belonging to the Symbiodiniaceae. Approximately 30,000 protein-coding genes were predicted in the D. trenchii genome, fewer than in other genomes from the Symbiodiniaceae. However, annotations revealed that the D. trenchii genome encodes a cluster of genes for synthesis of mycosporine-like amino acids, which absorb UV radiation. Interestingly, a neighboring gene in the cluster encodes a glucose-methanol-choline oxidoreductase with a flavin adenine dinucleotide domain that is also found in Symbiodinium tridacnidorum. This conservation seems to partially clarify an ancestral genomic structure in the Symbiodiniaceae and its loss in late-branching lineages, including Breviolum and Cladocopium, after splitting from the Durusdinium lineage. Our analysis suggests that approximately half of the taxa in the Symbiodiniaceae may maintain the ability to synthesize mycosporine-like amino acids. Thus, this work provides a significant genomic resource for understanding the genomic diversity of Symbiodiniaceae in corals.

SAGER: a database of Symbiodiniaceae and Algal Genomic Resource

Symbiodiniaceae dinoflagellates are essential endosymbionts of reef building corals and some other invertebrates. Information of their genome structure and function is critical for understanding coral symbiosis and bleaching. With the rapid development of sequencing technology, genome draft assemblies of several Symbiodiniaceae species and diverse marine algal genomes have become publicly available but spread in multiple separate locations. Here, we present a Symbiodiniaceae and Algal Genomic Resource Database (SAGER), a user-friendly online repository for integrating existing genomic data of Symbiodiniaceae species and diverse marine algal gene sets from MMETSP and PhyloDB databases. Relevant algal data are included to facilitate comparative analyses. The database is freely accessible at http://sampgr.org.cn. It provides comprehensive tools for studying gene function, expression and comparative genomics, including search tools to identify gene information from Symbiodiniaceae species, and BLAST tool to find orthologs from marine algae and protists. Moreover, SAGER integrates transcriptome datasets derived from diverse culture conditions of corresponding Symbiodiniaceae species. SAGER was developed with the capacity to incorporate future Symbiodiniaceae and algal genome and transcriptome data, and will serve as an open-access and sustained platform providing genomic and molecular tools that can be conveniently used to study Symbiodiniaceae and other marine algae. Database URL: http://sampgr.org.cn.