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
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]