July 2015 archive

Related Articles
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…

Related Articles
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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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]

Related Articles
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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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
…

Related Articles
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…