Sterol Composition and Biosynthetic Genes of the Recently Discovered Photosynthetic Alveolate, Chromera velia (Chromerida), a Close Relative of Apicomplexans

Abstract

Chromera velia is a recently discovered, photosynthetic, marine alveolate closely related to apicomplexan parasites, and more distantly to perkinsids and dinoflagellates. To date, there are no published studies on the sterols of C. velia. Because apicomplexans and perkinsids are not known to synthesize sterols de novo, but rather obtain them from their host organisms, our objective was to examine the composition of the sterols of C. velia to assess whether or not there is any commonality with dinoflagellates as the closest taxonomic group capable of synthesizing sterols de novo. Furthermore, knowledge of the sterols of C. velia may provide insight into the sterol biosynthetic capabilities of apicomplexans prior to loss of sterol biosynthesis. We have found that C. velia possesses two primary sterols, 24-ethylcholesta-5,22E-dien-3β-ol, and 24-ethylcholest-5-en-3β-ol, not common to dinoflagellates, but rather commonly found in other classes of algae and plants. In addition, we have identified computationally three genes, SMT1 (sterol-24C-methyltransferase), FDFT1 (farnesyl diphosphate farnesyl transferase, squalene synthase), and IDI1 (isopentenyl diphosphate Δ-isomerase), predicted to be involved in sterol biosynthesis by their similarity to analogous genes in other sterol-producing eukaryotes, including a number of algae.

Mono- and digalactosyldiacylglycerol composition of dinoflagellates. VI. Biochemical and genomic comparison of galactolipid biosynthesis betweenChromera velia(Chromerida), a photosynthetic alveolate with red algal plastid ancestry, and the dinoflagellate,Lingulodinium polyedrum

“…To date, despite the evolutionary importance of C. velia's plastid, there is a noticeable gap in knowledge of its lipid biochemistry, with only a single published study on the composition of C. velia's forms of MGDG and DGDG by Botté et al (2011) and a single published study on its sterol composition by Leblond et al (2012). In their recent study, Botté et al (2011) found major forms of MGDG and DGDG containing 20:5 at both the sn-1 and sn-2 positions, and minor forms containing 20:5 and 16:0 (regiochemistry undetermined).…”

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

“…), however, synthesize a wide variety of sterols de novo (Patterson , ), which does not generally include those produced by C. velia and V. brassicaformis (see discussion by Leblond et al. ).…”

“…24‐Ethylcholest‐5‐en‐3β‐ol is the predominant sterol in both V. brassicaformis and C. velia ; however, C. velia produces an additional array of sterols, namely 24‐methylcholesta‐5,22E‐dien‐3β‐ol and 24‐ethylcholesta‐5,22E‐dien‐3β‐ol, that are not found in V. brassicaformis but are commonly found in plant and other groups of algae but not in dinoflagellates (Leblond et al. ). Based on the KEGG reference pathway (Ogata et al.…”

“…A direct comparison of sterol composition cannot be made between apicomplexans and chromerids because apicomplexans do not synthesize sterols de novo (Coppens 2006), although they do possess the ability to synthesize other isoprenoid compounds (Guggisberg et al 2014) and to convert cholesterol to cholesteryl esters (Bott e et al 2013;Nishikawa et al 2005). Dinoflagellates, a closely related group to both chromerids and apicomplexans as based on ultrastructural and phylogenetic features (Janou skovec et al 2010; Moore et al 2008;Oborn ık et al 2012), however, synthesize a wide variety of sterols de novo (Patterson 1971(Patterson , 1991, which does not generally include those produced by C. velia and V. brassicaformis (see discussion by Leblond et al 2012). A Figure 3 Maximum likelihood tree generated by using RAxML with LG+G model for 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) protein sequence.…”

Increased growth and pigment content ofChromera veliain mixotrophic culture

“…The photosynthesis system of C. velia is highly efficient and adaptable to a range of light conditions owing to its specialised photoacclimation strategies (Kotabová et al ., ; Quigg et al ., ). Since its original isolation, published studies have cultured C. velia photoautotrophically in simple, inorganic growth media (Moore et al ., ; Guo et al ., ; Sutak et al ., ; Oborník et al ., ; Leblond et al ., ). Compared to the physical conditions, there has been relatively little exploration in terms of the nutritional factors of C. velia cultivation.…”