SxtA and sxtG Gene Expression and Toxin Production in the Mediterranean Alexandrium minutum (Dinophyceae)

Perini, Federico; Galluzzi, Luca; Dell’Aversano, Carmela; Iacovo, Emma Dello; Tartaglione, Luciana; Ricci, Fabio; Forino, Martino; Ciminiello, Patrizia; Penna, Antonella

doi:10.3390/md12105258

Cited by 43 publications

(37 citation statements)

References 56 publications

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“…For example, the gene expression pattern for sxtA4 in A. catenella examined by RT-qPCR did not significantly change under different growth stages, even though the saxitoxin production was significantly altered [45]. A similar expression pattern was also observed in sxtA and sxtG genes in A. minutum [49]. Examination by RNA-seq on the A. catenella transcriptome also revealed that most of the putative toxin gene transcripts varied insignificantly at different toxin biosynthesis stages [46].…”

Section: Recent Insight Into Saxitoxin Biosynthesis Through Transcripmentioning

confidence: 82%

“…More reports for translational control in dinoflagellates were found (Table 4), leading researchers to conclude that the expression of sxt genes in dinoflagellates is controlled at the post-transcriptional or post-translational level owing to the inconsistent expression level at the transcript level documented by previous studies [46,49] and the presence of a dinoflagellate splice-leader sequence in at least two core genes for saxitoxin biosynthesis [43,44]. However, as we are still traversing in the unknown genetic territory, gene expression at the transcript level in dinoflagellates cannot be completely overlooked.…”

Section: Translational Control In Dinoflagellates and Its Implicationmentioning

confidence: 99%

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Biosynthesis of Saxitoxin in Marine Dinoflagellates: An Omics Perspective

et al. 2020

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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.

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Section: Recent Insight Into Saxitoxin Biosynthesis Through Transcripmentioning

confidence: 82%

Section: Translational Control In Dinoflagellates and Its Implicationmentioning

confidence: 99%

Biosynthesis of Saxitoxin in Marine Dinoflagellates: An Omics Perspective

et al. 2020

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“…It appears that sxtA may not be strongly regulated at the transcriptional level in A. minutum, as toxin quantities were not well correlated with transcript abundance (Perini et al, 2014). Nevertheless, sxtA was found to be significantly down regulated in a non-toxic mutant strain of A. pacificum (Zhang et al, 2014).…”

Section: Introductionmentioning

confidence: 91%

“…Only limited information is available regarding the expression and function of sxtA copies (Perini et al, 2014;Zhang et al, 2014). It appears that sxtA may not be strongly regulated at the transcriptional level in A. minutum, as toxin quantities were not well correlated with transcript abundance (Perini et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Gene duplication, loss and selection in the evolution of saxitoxin biosynthesis in alveolates

Murray

Diwan

Orr

et al. 2015

Molecular Phylogenetics and Evolution

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a b s t r a c tA group of marine dinoflagellates (Alveolata, Eukaryota), consisting of $10 species of the genus Alexandrium, Gymnodinium catenatum and Pyrodinium bahamense, produce the toxin saxitoxin and its analogues (STX), which can accumulate in shellfish, leading to ecosystem and human health impacts. The genes, sxt, putatively involved in STX biosynthesis, have recently been identified, however, the evolution of these genes within dinoflagellates is not clear. There are two reasons for this: uncertainty over the phylogeny of dinoflagellates; and that the sxt genes of many species of Alexandrium and other dinoflagellate genera are not known. Here, we determined the phylogeny of STX-producing and other dinoflagellates based on a concatenated eight-gene alignment. We determined the presence, diversity and phylogeny of sxtA, domains A1 and A4 and sxtG in 52 strains of Alexandrium, and a further 43 species of dinoflagellates and thirteen other alveolates. We confirmed the presence and high sequence conservation of sxtA, domain A4, in 40 strains (35 Alexandrium, 1 Pyrodinium, 4 Gymnodinium) of 8 species of STX-producing dinoflagellates, and absence from non-producing species. We found three paralogs of sxtA, domain A1, and a widespread distribution of sxtA1 in non-STX producing dinoflagellates, indicating duplication events in the evolution of this gene. One paralog, clade 2, of sxtA1 may be particularly related to STX biosynthesis. Similarly, sxtG appears to be generally restricted to STX-producing species, while three amidinotransferase gene paralogs were found in dinoflagellates. We investigated the role of positive (diversifying) selection following duplication in sxtA1 and sxtG, and found negative selection in clades of sxtG and sxtA1, clade 2, suggesting they were functionally constrained. Significant episodic diversifying selection was found in some strains in clade 3 of sxtA1, a clade that may not be involved in STX biosynthesis, indicating pressure for diversification of function.

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“…Specific studies on toxic dinoflagellate species have led to the establishment of defined gene sets likely related to toxin production (Beedessee, Hisata, Roy, Satoh, & Shoguchi, ; Cusick & Sayler, ; Hackett et al., ; Kellmann, Stüken, Orr, Svendsen, & Jakobsen, ; Kohli et al., , ; Lehnert et al., ; Meyer et al., ; Monroe & Van Dolah, ; Murray, Diwan, Orr, Kohli, & John, ; Perini et al., ; Salcedo, Upadhyay, Nagasaki, & Bhattacharya, ; Sheng, Malkiel, Katz, Adolf, & Place, ; Snyder et al., ; Stüken et al., ; Wang, ; Zhang, Zhang, Lin, & Wang, ). PKS genes are present in all dinoflagellates (Kohli et al., ) but many of the toxic metabolites produced by some dinoflagellate species are of polyketide origin (Kellmann et al., ).…”

Section: Methodsmentioning

confidence: 99%

Analysis of the genomic basis of functional diversity in dinoflagellates using a transcriptome‐based sequence similarity network

et al. 2018

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Dinoflagellates are one of the most abundant and functionally diverse groups of eukaryotes. Despite an overall scarcity of genomic information for dinoflagellates, constantly emerging high-throughput sequencing resources can be used to characterize and compare these organisms. We assembled de novo and processed 46 dinoflagellate transcriptomes and used a sequence similarity network (SSN) to compare the underlying genomic basis of functional features within the group. This approach constitutes the most comprehensive picture to date of the genomic potential of dinoflagellates. A core-predicted proteome composed of 252 connected components (CCs) of putative conserved protein domains (pCDs) was identified. Of these, 206 were novel and 16 lacked any functional annotation in public databases. Integration of functional information in our network analyses allowed investigation of pCDs specifically associated with functional traits. With respect to toxicity, sequences homologous to those of proteins found in species with toxicity potential (e.g., sxtA4 and sxtG) were not specific to known toxin-producing species. Although not fully specific to symbiosis, the most represented functions associated with proteins involved in the symbiotic trait were related to membrane processes and ion transport. Overall, our SSN approach led to identification of 45,207 and 90,794 specific and constitutive pCDs of, respectively, the toxic and symbiotic species represented in our analyses. Of these, 56% and 57%, respectively (i.e., 25,393 and 52,193 pCDs), completely lacked annotation in public databases. This stresses the extent of our lack of knowledge, while emphasizing the potential of SSNs to identify candidate pCDs for further functional genomic characterization.

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SxtA and sxtG Gene Expression and Toxin Production in the Mediterranean Alexandrium minutum (Dinophyceae)

Cited by 43 publications

References 56 publications

Biosynthesis of Saxitoxin in Marine Dinoflagellates: An Omics Perspective

Biosynthesis of Saxitoxin in Marine Dinoflagellates: An Omics Perspective

Gene duplication, loss and selection in the evolution of saxitoxin biosynthesis in alveolates

Analysis of the genomic basis of functional diversity in dinoflagellates using a transcriptome‐based sequence similarity network

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