Characterization and localization of a hybrid non-ribosomal peptide synthetase and polyketide synthase gene from the toxic dinoflagellate Karenia brevis

A decade of dinoflagellate genomics illuminating an enigmatic eukaryote cell

Dinoflagellates are a remarkable group of protists, not only for their association with harmful algal blooms and coral reefs but also for their numerous characteristics deviating from the rules of eukaryotic biology. Genome research on dinoflagellates has lagged due to their immense genome sizes in most species (~ 1-250 Gbp). Nevertheless, the last decade marked a fruitful era of dinoflagellate genomics, with 27 genomes sequenced and many insights attained. This review aims to synthesize information from these genomes, along with other omic data, to reflect on where we are now in understanding dinoflagellates and where we are heading in the future. The most notable insights from the decade-long genomics work include: (1) dinoflagellate genomes have been expanded in multiple times independently, probably by a combination of rampant retroposition, accumulation of repetitive DNA, and genome duplication; (2) Symbiodiniacean genomes are highly divergent, but share about 3,445 core unigenes concentrated in 219 KEGG pathways; (3) Most dinoflagellate genes are encoded unidirectionally and are not intron-poor; (4) The dinoflagellate nucleus has undergone extreme evolutionary changes, including complete or nearly complete loss of nucleosome and histone H1, and acquisition of dinoflagellate viral nuclear protein (DVNP); (5) Major basic nuclear protein (MBNP), histone-like protein (HLP), and bacterial HU-like protein (HCc) belong to the same protein family, and MBNP can be the unifying name; (6) Dinoflagellate gene expression is regulated by poorly understood mechanisms, but microRNA and other epigenetic mechanisms are likely important; (7) Over 50% of dinoflagellate genes are "dark" and their functions remain to be deciphered using functional genetics; (8) Initial insights into the genomic basis of parasitism and mutualism have emerged. The review then highlights functionally unique and interesting genes. Future research needs to obtain a finished genome, tackle large genomes, characterize the unknown genes, and develop a quantitative molecular ecological model for addressing ecological questions.

De novo Transcriptome of the Non-saxitoxin Producing Alexandrium tamutum Reveals New Insights on Harmful Dinoflagellates

Many dinoflagellates species, especially of the Alexandrium genus, produce a series of toxins with tremendous impacts on human and environmental health, and tourism economies. Alexandrium tamutum was discovered for the first time in the Gulf of Naples, and it is not known to produce saxitoxins. However, a clone of A. tamutum from the same Gulf showed copepod reproduction impairment and antiproliferative activity. In this study, the full transcriptome of the dinoflagellate A. tamutum is presented in both control and phosphate starvation conditions. RNA-seq approach was used for in silico identification of transcripts that can be involved in the synthesis of toxic compounds. Phosphate starvation was selected because it is known to induce toxin production for other Alexandrium spp. Results showed the presence of three transcripts related to saxitoxin synthesis (sxtA, sxtG and sxtU), and others potentially related to the synthesis of additional toxic compounds (e.g., 44 transcripts annotated as "polyketide synthase"). These data suggest that even if this A. tamutum clone does not produce saxitoxins, it has the potential to produce toxic metabolites, in line with the previously observed activity. These data give new insights into toxic microalgae, toxin production and their potential applications for the treatment of human pathologies.

Transcriptome survey and toxin measurements reveal evolutionary modification and loss of saxitoxin biosynthesis genes in the dinoflagellates Amphidinium carterae and Prorocentrum micans

In the present study, we characterized the potential toxin genes for polyketide synthase (PKS) and saxitoxin (STX) biosynthesis using the transcriptomes of two non-STX producing dinoflagellates Amphidinium carterae and Prorocentrum micans. RNA sequencing revealed 94 and 166 PKS contigs in A. carterae and P. micans, respectively. We first detected type III PKS, which was closely related to bacteria. In addition, dozens of homologs of 20 STX biosynthesis genes were identified. Interestingly, the core STX-synthesizing genes sxtA and sxtB were only found in P. micans, whereas sxtD was detected in A. carterae alone. Bioinformatic analysis showed that the first two core genes (sxtA and sxtG) had a low sequence similarity (37.0-67.6%) and different domain organization compared to those of other toxigenic dinoflagellates, such as Alexandrium pacificum. These might result in the breakdown of the initial reactions in STX production and ultimately the loss of the ability to synthesize the toxins in both dinoflagellates. Our findings suggest that toxin-related PKS and sxt genes are commonly found in non-STX producing dinoflagellates. In addition to their involvement in the synthesis of toxins, our result indicates that genes may also have other molecular metabolic functions.

Comparative transcriptomics of toxin synthesis genes between the non-toxin producing dinoflagellate Cochlodinium polykrikoides and toxigenic Alexandrium pacificum

In the present study, we extensively characterized potential toxin-related genes, including polyketide synthase (PKS), saxitoxin (STX) and fatty acid synthase (FAS) from the non-toxin producing marine dinoflagellate Cochlodinium polykrikoides, comparing to those of a toxigenic dinoflagellate Alexandrium pacificum. RNA sequencing revealed 50 and 271 PKS contigs from C. polykrikoides and A. pacificum, respectively. According to domain constitute and amino acid alteration, we further classified the dinoflagellate type I PKS genes into 4 sub-groups. Type III PKS was first identified in C. polykrikoides. Interestingly, we detected a large number (242 and 288) of homologs of 18 sxt genes from two studied dinoflagellates. Most of the eight key genes (sxtA, sxtB, sxtD, sxtG, sxtH/T, sxtI, sxtS and sxtU) for STX synthesis were detected in both dinoflatellates, whereas a core STX biosynthesis gene sxtG was not detected in C. polykrikoides. This may partially explain the absence of saxitoxin production in C. polykrikoides. In addition, we identified several type I and type II FAS genes, including FabD, FabF, FabG, FabH, FabI, and FabZ, whereas FabB was not found in C. polykrikoides. Overall, the numbers of the toxin-related genes in C. polykrikoides were less than that of A. pacificum. Phylogenetic analyses showed that type I PKS/FASs of dinoflagellates had close relationships with apicomplexans and bacteria. These suggest that the toxin-related PKS and sxt genes are commonly present in toxigenic and non-toxin producing dinoflagellates, and may be involved not only in the toxin synthesis, but also in other related molecular metabolic functions.

Biosynthesis of Saxitoxin in Marine Dinoflagellates: An Omics Perspective

Saxitoxin is an alkaloid neurotoxin originally isolated from the clam Saxidomus giganteus in 1957. This group of neurotoxins is produced by several species of freshwater cyanobacteria and marine dinoflagellates. The saxitoxin biosynthesis pathway was described for the first time in the 1980s and, since then, it was studied in more than seven cyanobacterial genera, comprising 26 genes that form a cluster ranging from 25.7 kb to 35 kb in sequence length. Due to the complexity of the genomic landscape, saxitoxin biosynthesis in dinoflagellates remains unknown. In order to reveal and understand the dynamics of the activity in such impressive unicellular organisms with a complex genome, a strategy that can carefully engage them in a systems view is necessary. Advances in omics technology (the collective tools of biological sciences) facilitated high-throughput studies of the genome, transcriptome, proteome, and metabolome of dinoflagellates. The omics approach was utilized to address saxitoxin-producing dinoflagellates in response to environmental stresses to improve understanding of dinoflagellates gene–environment interactions. Therefore, in this review, the progress in understanding dinoflagellate saxitoxin biosynthesis using an omics approach is emphasized. Further potential applications of metabolomics and genomics to unravel novel insights into saxitoxin biosynthesis in dinoflagellates are also reviewed.

Research Progress in the Biosynthetic Mechanisms of Marine Polyether Toxins

Marine polyether toxins, mainly produced by marine dinoflagellates, are novel, complex, and diverse natural products with extensive toxicological and pharmacological effects. Owing to their harmful effects during outbreaks of marine red tides, as well as their potential value for the development of new drugs, marine polyether toxins have been extensively studied, in terms of toxicology, pharmacology, detection, and analysis, structural identification, as well as their biosynthetic mechanisms. Although the biosynthetic mechanisms of marine polyether toxins are still unclear, certain progress has been made. In this review, research progress and current knowledge on the biosynthetic mechanisms of polyether toxins are summarized, including the mechanisms of carbon skeleton deletion, pendant alkylation, and polyether ring formation, along with providing a summary of mined biosynthesis-related genes. Finally, future research directions and applications of marine polyether toxins are discussed.

Microalgal Enzymes with Biotechnological Applications

Enzymes are essential components of biological reactions and play important roles in the scaling and optimization of many industrial processes. Due to the growing commercial demand for new and more efficient enzymes to help further optimize these processes, many studies are now focusing their attention on more renewable and environmentally sustainable sources for the production of these enzymes. Microalgae are very promising from this perspective since they can be cultivated in photobioreactors, allowing the production of high biomass levels in a cost-efficient manner. This is reflected in the increased number of publications in this area, especially in the use of microalgae as a source of novel enzymes. In particular, various microalgal enzymes with different industrial applications (e.g., lipids and biofuel production, healthcare, and bioremediation) have been studied to date, and the modification of enzymatic sequences involved in lipid and carotenoid production has resulted in promising results. However, the entire biosynthetic pathways/systems leading to synthesis of potentially important bioactive compounds have in many cases yet to be fully characterized (e.g., for the synthesis of polyketides). Nonetheless, with recent advances in microalgal genomics and transcriptomic approaches, it is becoming easier to identify sequences encoding targeted enzymes, increasing the likelihood of the identification, heterologous expression, and characterization of these enzymes of interest. This review provides an overview of the state of the art in marine and freshwater microalgal enzymes with potential biotechnological applications and provides future perspectives for this field.

The Genetic Basis of Toxin Biosynthesis in Dinoflagellates

In marine ecosystems, dinoflagellates can become highly abundant and even dominant at times, despite their comparatively slow growth rates. One factor that may play a role in their ecological success is the production of complex secondary metabolite compounds that can have anti-predator, allelopathic, or other toxic effects on marine organisms, and also cause seafood poisoning in humans. Our knowledge about the genes involved in toxin biosynthesis in dinoflagellates is currently limited due to the complex genomic features of these organisms. Most recently, the sequencing of dinoflagellate transcriptomes has provided us with valuable insights into the biosynthesis of polyketide and alkaloid-based toxin molecules in dinoflagellate species. This review synthesizes the recent progress that has been made in understanding the evolution, biosynthetic pathways, and gene regulation in dinoflagellates with the aid of transcriptomic and other molecular genetic tools, and provides a pathway for future studies of dinoflagellates in this exciting omics era.

Diversified secondary metabolite biosynthesis gene repertoire revealed in symbiotic dinoflagellates

Symbiodiniaceae dinoflagellates possess smaller nuclear genomes than other dinoflagellates and produce structurally specialized, biologically active, secondary metabolites. Till date, little is known about the evolution of secondary metabolism in dinoflagellates as comparative genomic approaches have been hampered by their large genome sizes. Here, we overcome this challenge by combining genomic and metabolomics approaches to investigate how chemical diversity arises in three decoded Symbiodiniaceae genomes (clades A3, B1 and C). Our analyses identify extensive diversification of polyketide synthase and non-ribosomal peptide synthetase genes from two newly decoded genomes of Symbiodinium tridacnidorum (A3) and Cladocopium sp. (C). Phylogenetic analyses indicate that almost all the gene families are derived from lineage-specific gene duplications in all three clades, suggesting divergence for environmental adaptation. Few metabolic pathways are conserved among the three clades and we detect metabolic similarity only in the recently diverged clades, B1 and C. We establish that secondary metabolism protein architecture guides substrate specificity and that gene duplication and domain shuffling have resulted in diversification of secondary metabolism genes.

Interaction of a dinoflagellate neurotoxin with voltage-activated ion channels in a marine diatom

Background

The potent neurotoxins produced by the harmful algal bloom species Karenia brevis are activators of sodium voltage-gated channels (VGC) in animals, resulting in altered channel kinetics and membrane hyperexcitability. Recent biophysical and genomic evidence supports widespread presence of homologous sodium (Na⁺) and calcium (Ca²⁺) permeable VGCs in unicellular algae, including marine phytoplankton. We therefore hypothesized that VGCs of these phytoplankton may be an allelopathic target for waterborne neurotoxins produced by K. brevis blooms that could lead to ion channel dysfunction and disruption of signaling in a similar manner to animal Na⁺ VGCs.

Methods

We examined the interaction of brevetoxin-3 (PbTx-3), a K. brevis neurotoxin, with the Na⁺/Ca²⁺ VGC of the non-toxic diatom Odontella sinensis using electrophysiology. Single electrode current- and voltage- clamp recordings from O. sinensis in the presence of PbTx-3 were used to examine the toxin’s effect on voltage gated Na⁺/Ca²⁺ currents. In silico analysis was used to identify the putative PbTx binding site in the diatoms. We identified Na⁺/Ca²⁺ VCG homologs from the transcriptomes and genomes of 12 diatoms, including three transcripts from O. sinensis and aligned them with site-5 of Na⁺ VGCs, previously identified as the PbTx binding site in animals.

Results

Up to 1 µM PbTx had no effect on diatom resting membrane potential or membrane excitability. The kinetics of fast inward Na⁺/Ca²⁺ currents that underlie diatom action potentials were also unaffected. However, the peak inward current was inhibited by 33%, delayed outward current was inhibited by 25%, and reversal potential of the currents shifted positive, indicating a change in permeability of the underlying channels. Sequence analysis showed a lack of conservation of the PbTx binding site in diatom VGC homologs, many of which share molecular features more similar to single-domain bacterial Na⁺/Ca²⁺ VGCs than the 4-domain eukaryote channels.

Discussion

Although membrane excitability and the kinetics of action potential currents were unaffected, the permeation of the channels underlying the diatom action potential was significantly altered in the presence of PbTx-3. However, at environmentally relevant concentrations the effects of PbTx- on diatom voltage activated currents and interference of cell signaling through this pathway may be limited. The relative insensitivity of phytoplankton VGCs may be due to divergence of site-5 (the putative PbTx binding site), and in some cases, such as O. sinensis, resistance to toxin effects may be because of evolutionary loss of the 4-domain eukaryote channel, while retaining a single domain bacterial-like VGC that can substitute in the generation of fast action potentials.

Both modular and single-domain Type I polyketide synthases are expressed in the brevetoxin-producing dinoflagellate, Karenia brevis (Dinophyceae)

Dinoflagellates are prolific producers of polyketide compounds, many of which are potent toxins with adverse impacts on human and marine animal health. To identify polyketide synthase (PKS) genes in the brevetoxin-producing dinoflagellate, Karenia brevis, we assembled a transcriptome from 595 million Illumina reads, sampled under different growth conditions. The assembly included 125,687 transcripts greater than 300 nt in length, with over half having >100× coverage. We found 121 transcripts encoding Type I ketosynthase (KS) domains, of which 99 encoded single KS domains, while 22 contained multiple KS domains arranged in 1-3 protein modules. Phylogenetic analysis placed all single domain and a majority of multidomain KSs within a monophyletic clade of protist PKSs. In contrast with the highly amplified single-domain KSs, only eight single-domain ketoreductase transcripts were found in the assembly, suggesting that they are more evolutionarily conserved. The multidomain PKSs were dominated by trans-acyltransferase architectures, which were recently shown to be prevalent in other algal protists. Karenia brevis also expressed several hybrid nonribosomal peptide synthetase (NRPS)/PKS sequences, including a burA-like sequence previously reported in a wide variety of dinoflagellates. This contrasts with a similarly deep transcriptome of Gambierdiscus polynesiensis, which lacked NRPS/PKS other than the burA-like transcript, and may reflect the presence of amide-containing polyketides in K. brevis and their absence from G. polynesiensis. In concert with other recent transcriptome analyses, this study provides evidence for both single domain and multidomain PKSs in the synthesis of polyketide compounds in dinoflagellates.

Genomic insights into the distribution, genetic diversity and evolution of polyketide synthases and nonribosomal peptide synthetases

Polyketides and nonribosomal peptides are important secondary metabolites that exhibit enormous structural diversity, have many pharmaceutical applications, and include a number of clinically important drugs. These complex metabolites are most commonly synthesized on enzymatic assembly lines of polyketide synthases and nonribosomal peptide synthetases. Genome-mining studies making use of the recent explosion in the number of genome sequences have demonstrated unexpected enzymatic diversity and greatly expanded the known distribution of these enzyme systems across the three domains of life. The wealth of data now available suggests that genome-mining efforts will uncover new natural products, novel biosynthetic mechanisms, and shed light on the origin and evolution of these important enzymes.

Multifunctional polyketide synthase genes identified by genomic survey of the symbiotic dinoflagellate, Symbiodinium minutum

Background

Dinoflagellates are unicellular marine and freshwater eukaryotes. They possess large nuclear genomes (1.5–245 gigabases) and produce structurally unique and biologically active polyketide secondary metabolites. Although polyketide biosynthesis is well studied in terrestrial and freshwater organisms, only recently have dinoflagellate polyketides been investigated. Transcriptomic analyses have characterized dinoflagellate polyketide synthase genes having single domains. The Genus Symbiodinium, with a comparatively small genome, is a group of major coral symbionts, and the S. minutum nuclear genome has been decoded.

Results

The present survey investigated the assembled S. minutum genome and identified 25 candidate polyketide synthase (PKS) genes that encode proteins with mono- and multifunctional domains. Predicted proteins retain functionally important amino acids in the catalytic ketosynthase (KS) domain. Molecular phylogenetic analyses of KS domains form a clade in which S. minutum domains cluster within the protist Type I PKS clade with those of other dinoflagellates and other eukaryotes. Single-domain PKS genes are likely expanded in dinoflagellate lineage. Two PKS genes of bacterial origin are found in the S. minutum genome. Interestingly, the largest enzyme is likely expressed as a hybrid non-ribosomal peptide synthetase-polyketide synthase (NRPS-PKS) assembly of 10,601 amino acids, containing NRPS and PKS modules and a thioesterase (TE) domain. We also found intron-rich genes with the minimal set of catalytic domains needed to produce polyketides. Ketosynthase (KS), acyltransferase (AT), and acyl carrier protein (ACP) along with other optional domains are present. Mapping of transcripts to the genome with the dinoflagellate-specific spliced leader sequence, supports expression of multifunctional PKS genes. Metabolite profiling of cultured S. minutum confirmed production of zooxanthellamide D, a polyhydroxy amide polyketide and other unknown polyketide secondary metabolites.

Conclusion

This genomic survey demonstrates that S. minutum contains genes with the minimal set of catalytic domains needed to produce polyketides and provides evidence of the modular nature of Type I PKS, unlike monofunctional Type I PKS from other dinoflagellates. In addition, our study suggests that diversification of dinoflagellate PKS genes comprises dinoflagellate-specific PKS genes with single domains, multifunctional PKS genes with KS domains orthologous to those of other protists, and PKS genes of bacterial origin.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2195-8) contains supplementary material, which is available to authorized users.

RNA Sequencing Revealed Numerous Polyketide Synthase Genes in the Harmful Dinoflagellate Karenia mikimotoi

The dinoflagellate Karenia mikimotoi forms blooms in the coastal waters of temperate regions and occasionally causes massive fish and invertebrate mortality. This study aimed to elucidate the toxic effect of K. mikimotoi on marine organisms by using the genomics approach; RNA-sequence libraries were constructed, and data were analyzed to identify toxin-related genes. Next-generation sequencing produced 153,406 transcript contigs from the axenic culture of K. mikimotoi. BLASTX analysis against all assembled contigs revealed that 208 contigs were polyketide synthase (PKS) sequences. Thus, K. mikimotoi was thought to have several genes encoding PKS metabolites and to likely produce toxin-like polyketide molecules. Of all the sequences, approximately 30 encoded eight PKS genes, which were remarkably similar to those of Karenia brevis. Our phylogenetic analyses showed that these genes belonged to a new group of PKS type-I genes. Phylogenetic and active domain analyses showed that the amino acid sequence of four among eight Karenia PKS genes was not similar to any of the reported PKS genes. These PKS genes might possibly be associated with the synthesis of polyketide toxins produced by Karenia species. Further, a homology search revealed 10 contigs that were similar to a toxin gene responsible for the synthesis of saxitoxin (sxtA) in the toxic dinoflagellate Alexandrium fundyense. These contigs encoded A1-A3 domains of sxtA genes. Thus, this study identified some transcripts in K. mikimotoi that might be associated with several putative toxin-related genes. The findings of this study might help understand the mechanism of toxicity of K. mikimotoi and other dinoflagellates.

Atlas of nonribosomal peptide and polyketide biosynthetic pathways reveals common occurrence of nonmodular enzymes

Nonribosomal peptides and polyketides are a diverse group of natural products with complex chemical structures and enormous pharmaceutical potential. They are synthesized on modular nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) enzyme complexes by a conserved thiotemplate mechanism. Here, we report the widespread occurrence of NRPS and PKS genetic machinery across the three domains of life with the discovery of 3,339 gene clusters from 991 organisms, by examining a total of 2,699 genomes. These gene clusters display extraordinarily diverse organizations, and a total of 1,147 hybrid NRPS/PKS clusters were found. Surprisingly, 10% of bacterial gene clusters lacked modular organization, and instead catalytic domains were mostly encoded as separate proteins. The finding of common occurrence of nonmodular NRPS differs substantially from the current classification. Sequence analysis indicates that the evolution of NRPS machineries was driven by a combination of common descent and horizontal gene transfer. We identified related siderophore NRPS gene clusters that encoded modular and nonmodular NRPS enzymes organized in a gradient. A higher frequency of the NRPS and PKS gene clusters was detected from bacteria compared with archaea or eukarya. They commonly occurred in the phyla of Proteobacteria, Actinobacteria, Firmicutes, and Cyanobacteria in bacteria and the phylum of Ascomycota in fungi. The majority of these NRPS and PKS gene clusters have unknown end products highlighting the power of genome mining in identifying novel genetic machinery for the biosynthesis of secondary metabolites.

Putative monofunctional type I polyketide synthase units: a dinoflagellate-specific feature?

Marine dinoflagellates (alveolata) are microalgae of which some cause harmful algal blooms and produce a broad variety of most likely polyketide synthesis derived phycotoxins. Recently, novel polyketide synthesase (PKS) transcripts have been described from the Florida red tide dinoflagellate Karenia brevis (gymnodiniales) which are evolutionarily related to Type I PKS but were apparently expressed as monofunctional proteins, a feature typical of Type II PKS. Here, we investigated expression units of PKS I-like sequences in Alexandrium ostenfeldii (gonyaulacales) and Heterocapsa triquetra (peridiniales) at the transcript and protein level. The five full length transcripts we obtained were all characterized by polyadenylation, a 3′ UTR and the dinoflagellate specific spliced leader sequence at the 5′end. Each of the five transcripts encoded a single ketoacylsynthase (KS) domain showing high similarity to K. brevis KS sequences. The monofunctional structure was also confirmed using dinoflagellate specific KS antibodies in Western Blots. In a maximum likelihood phylogenetic analysis of KS domains from diverse PKSs, dinoflagellate KSs formed a clade placed well within the protist Type I PKS clade between apicomplexa, haptophytes and chlorophytes. These findings indicate that the atypical PKS I structure, i.e., expression as putative monofunctional units, might be a dinoflagellate specific feature. In addition, the sequenced transcripts harbored a previously unknown, apparently dinoflagellate specific conserved N-terminal domain. We discuss the implications of this novel region with regard to the putative monofunctional organization of Type I PKS in dinoflagellates.

Bioactives from microalgal dinoflagellates

Dinoflagellate microalgae are an important source of marine biotoxins. Bioactives from dinoflagellates are attracting increasing attention because of their impact on the safety of seafood and potential uses in biomedical, toxicological and pharmacological research. Here we review the potential applications of dinoflagellate toxins and the methods for producing them. Only sparing quantities of dinoflagellate toxins are generally available and this hinders bioactivity characterization and evaluation in possible applications. Approaches to production of increased quantities of dinoflagellate bioactives are discussed. Although many dinoflagellates are fragile and grow slowly, controlled culture in bioreactors appears to be generally suitable for producing many of the metabolites of interest.

Biosynthesis and molecular genetics of polyketides in marine dinoflagellates

Marine dinoflagellates are the single most important group of algae that produce toxins, which have a global impact on human activities. The toxins are chemically diverse, and include macrolides, cyclic polyethers, spirolides and purine alkaloids. Whereas there is a multitude of studies describing the pharmacology of these toxins, there is limited or no knowledge regarding the biochemistry and molecular genetics involved in their biosynthesis. Recently, however, exciting advances have been made. Expressed sequence tag sequencing studies have revealed important insights into the transcriptomes of dinoflagellates, whereas other studies have implicated polyketide synthase genes in the biosynthesis of cyclic polyether toxins, and the molecular genetic basis for the biosynthesis of paralytic shellfish toxins has been elucidated in cyanobacteria. This review summarises the recent progress that has been made regarding the unusual genomes of dinoflagellates, the biosynthesis and molecular genetics of dinoflagellate toxins. In addition, the evolution of these metabolic pathways will be discussed, and an outlook for future research and possible applications is provided.