The Genetic Basis of Toxin Biosynthesis in Dinoflagellates

Abstract

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.

Transcriptomic investigation into polyketide toxin synthesis in Ostreopsis (Dinophyceae) species

“…Such mechanisms would restrict the accumulation of deleterious mutations and also provides protection from reactive oxygen species generated during the process of photosynthesis (Kohli et al ., ). As fatty acid synthesis is essential for survival, these genes were likely retained by protists in the nucleus due to strong selective pressure (Verma et al ., and references therein). Amongst dinoflagellates, their evolution broadly follows a similar trend as reported by ribosomal gene phylogenies highlighting the conserved nature of FAS domains amongst the reported species (Fig.…”

“…This implies that numerous PKS domains, including both single and multi-, work together on the biosynthesis of PLTX-like compounds and also other related polyketide compounds (Van Dolah et al, 2017). Alongside PKS gene clusters, other gene families have also been reported from recent studies that facilitate toxin production and secretion, however, their use in toxic dinoflagellates remains to be fully investigated (Stephens et al, 2018;Verma et al, 2019 and references therein). The PKS domains reported in this study have divergent homologues, belonging to different phylogenetic sub-clades and producing diverse range of secondary metabolites, however, no specific PLTX-like compounds producing-or species-specific sub-clades could be observed in our phylogenetic analyses ( Figs.…”

Biosynthesis of Saxitoxin in Marine Dinoflagellates: An Omics Perspective

“…Alongside the lethal saxitoxins of purine alkaloids, dinoflagellates also produce other toxins of spirolides, macrolides, and cyclic polyethers, for which definitive roles are still incognito to researchers. The arduous molecular characterization of their biosynthetic pathways can only be effectively uncovered with biochemical information [121].…”

Ciguatera Fish Poisoning: The Risk from an Aotearoa/New Zealand Perspective

“…Gene catalogues have been produced for the CTXs producers G. polynesiensis and G. excentricus and, in addition to a vast diversity of PKS genes being detected, a clear distinction has been made between those genes responsible for fatty acid and polyketide biosynthesis in Gambierdiscus [65,66]. It is likely that many genes are associated with CTXs production and dinoflagellates may also produce a variety of diverse PKS-related compounds, making it even more difficult to link specific pathways and compounds [67]. The finding that the average toxicity (Table 2) of a species may be inversely proportional to growth rate suggests that there may be an evolutionary trade-off between toxin production (possibly for defence) and growth [22].…”