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Ancient origin of the biosynthesis of lignin precursors.
Biol Direct. 2015;10:23
Authors: Labeeuw L, Martone PT, Boucher Y, Case RJ
Abstract
BACKGROUND: Lignin plays an important r…

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Integration of plastids with their hosts: Lessons learned from dinoflagellates.
Proc Natl Acad Sci U S A. 2015 May 20;
Authors: Dorrell RG, Howe CJ
Abstract
After their endosymbiotic…

Sterol Composition and Biosynthetic Genes of Vitrella brassicaformis, A Recently Discovered Chromerid: Comparison to Chromera velia and Phylogenetic Relationship to Apicomplexan Parasites.

J Eukaryot Microbiol. 2015 May 20;

Authors: Khadka M, Salem M, Leblond JD

Abstract
Vitrella brassicaformis is the second discovered species in the Chromerida, and first in the family Vitrellaceae. Chromera velia, the first discovered species, forms an independent photosynthetic lineage with V. brassicaformis, and both are closely related to peridinin-containing dinoflagellates and non-photosynthetic apicomplexans; both also show phylogenetic closeness with red algal plastids.. We have utilized gas chromatography/mass spectrometry (GC/MS) to identify two free sterols, 24-ethylcholest-5-en-3β-ol, and a minor unknown sterol which appeared to be a C28:4 compound. We have also used RNA Seq analysis to identify seven genes found in the non-mevalonate/methylerythritol pathway (MEP) for sterol biosynthesis. Subsequent genome analysis of V. brassicaformis showed the presence of two mevalonate (MVA) pathway genes, though the genes were not observed in the transcriptome analysis. Transcripts from four genes (dxr, ispf, ispd, and idi) were selected and translated into proteins to study the phylogenetic relationship of sterol biosynthesis in V. brassicaformis and C. velia to other groups of algae and apicomplexans. Based on our genomic and transcriptomic analyses, we hypothesize that the MEP pathway was the primary pathway that apicomplexans used for sterol biosynthesis before they lost their sterol biosynthesis ability, although contribution of the MVA pathway cannot be discounted. This article is protected by copyright. All rights reserved.

PMID: 25996517 [PubMed – as supplied by publisher]

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The Plastid Genome of the Cryptomonad Teleaulax amphioxeia.
PLoS One. 2015;10(6):e0129284
Authors: Kim JI, Yoon HS, Yi G, Kim HS, Yih W, Shin W
Abstract
Teleaulax amphioxeia is a p…

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Polyketide synthesis genes associated with toxin production in two species of Gambierdiscus (Dinophyceae).

BMC Genomics. 2015;16:410

Authors: Kohli GS, John U, Figueroa RI, Rhodes LL, Harwood DT, Groth M, Bolch CJ, Murray SA

Abstract
BACKGROUND: Marine microbial protists, in particular, dinoflagellates, produce polyketide toxins with ecosystem-wide and human health impacts. Species of Gambierdiscus produce the polyether ladder compounds ciguatoxins and maitotoxins, which can lead to ciguatera fish poisoning, a serious human illness associated with reef fish consumption. Genes associated with the biosynthesis of polyether ladder compounds are yet to be elucidated, however, stable isotope feeding studies of such compounds consistently support their polyketide origin indicating that polyketide synthases are involved in their biosynthesis.
RESULTS: Here, we report the toxicity, genome size, gene content and transcriptome of Gambierdiscus australes and G. belizeanus. G. australes produced maitotoxin-1 and maitotoxin-3, while G. belizeanus produced maitotoxin-3, for which cell extracts were toxic to mice by IP injection (LD50 = 3.8 mg kg(-1)). The gene catalogues comprised 83,353 and 84,870 unique contigs, with genome sizes of 32.5 ± 3.7 Gbp and 35 ± 0.88 Gbp, respectively, and are amongst the most comprehensive yet reported from a dinoflagellate. We found three hundred and six genes involved in polyketide biosynthesis, including one hundred and ninty-two ketoacyl synthase transcripts, which formed five unique phylogenetic clusters.
CONCLUSIONS: Two clusters were unique to these maitotoxin-producing dinoflagellate species, suggesting that they may be associated with maitotoxin biosynthesis. This work represents a significant step forward in our understanding of the genetic basis of polyketide production in dinoflagellates, in particular, species responsible for ciguatera fish poisoning.

PMID: 26016672 [PubMed – in process]

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Heat Shock Protein 70 and 90 Genes in the Harmful Dinoflagellate Cochlodinium polykrikoides: Genomic Structures and Transcriptional Responses to Environmental Stresses.
Int J Genomics. 2015;2015:484626
…

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Eye-like ocelloids are built from different endosymbiotically acquired components.
Nature. 2015 Jul 1;
Authors: Gavelis GS, Hayakawa S, White Iii RA, Gojobori T, Suttle CA, Keeling PJ, Leander BS
…

Culture-Independent Study of the Late-Stage of a Bloom of the Toxic Dinoflagellate Ostreopsis cf. ovata: Preliminary Findings Suggest Genetic Differences at the Sub-Species Level and Allow ITS2 Structure Characterization.
T…

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Paralytic shellfish toxin content is related to genomic sxtA4 copy number in Alexandrium minutum strains.

Front Microbiol. 2015;6:404

Authors: Stüken A, Riobó P, Franco J, Jakobsen KS, Guillou L, Figueroa RI

Abstract
Dinoflagellates are microscopic aquatic eukaryotes with huge genomes and an unusual cell regulation. For example, most genes are present in numerous copies and all copies seem to be obligatorily transcribed. The consequence of the gene copy number (CPN) for final protein synthesis is, however, not clear. One such gene is sxtA, the starting gene of paralytic shellfish toxin (PST) synthesis. PSTs are small neurotoxic compounds that can accumulate in the food chain and cause serious poisoning incidences when ingested. They are produced by dinoflagellates of the genera Alexandrium, Gymnodium, and Pyrodinium. Here we investigated if the genomic CPN of sxtA4 is related to PST content in Alexandrium minutum cells. SxtA4 is the 4th domain of the sxtA gene and its presence is essential for PST synthesis in dinoflagellates. We used PST and genome size measurements as well as quantitative PCR to analyze sxtA4 CPN and toxin content in 15 A. minutum strains. Our results show a strong positive correlation between the sxtA4 CPN and the total amount of PST produced in actively growing A. minutum cells. This correlation was independent of the toxin profile produced, as long as the strain contained the genomic domains sxtA1 and sxtA4.

PMID: 25983733 [PubMed]