Acyl-CoA elongase activity and gene from the marine microalga Pavlova lutheri (Haptophyceae)
ABSTRACT Microsomal elongases are proteins catalyzing the condensation of malonyl-CoA with acyl-CoA chains, the first and rate-limiting step in microsomal fatty acid elongation. Here we report the measurement of elongase activity of a microsomal enriched fraction from the marine microalga Pavlova lutheri (P. lutheri). By directly monitoring the production of C2 elongated acyl-CoA from a range of saturated and monounsaturated acyl-CoA substrates, we found that saturated 16:0-CoA is the preferred substrate for this elongase complex. Analysis of an EST database prepared from the exponential stage of growth of P. lutheri revealed the most abundant identifiable enzyme as a cDNA, Plelo1, encoding a protein similar to the plant β-ketoacyl-coenzyme A synthases (KCS, also known as elongases). Plelo1 is a single copy gene in the algal genome and gene expression analysis showed it to be highly expressed during the exponential phase of growth. It is suggested that microsomal elongation of 16:0-CoA represents a key intermediate step in the biosynthesis of the health beneficial very long chain polyunsaturated fatty acids eicosapentaenoic (20:5n3) and docosahexaenoic (22:6n3) acids.
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ABSTRACT: The Pavlovophyceae (Haptophyta) contains four genera (Pavlova, Diacronema, Exanthemachrysis and Rebecca) and only thirteen characterised species, several of which are important in ecological and economic contexts. We have constructed molecular phylogenies inferred from sequencing of ribosomal gene markers with comprehensive coverage of the described diversity, using type strains when available, together with additional cultured strains. The morphology and ultrastructure of 12 of the described species was also re-examined and the pigment signatures of many culture strains were determined. The molecular analysis revealed that sequences of all described species differed, although those of Pavlova gyrans and P. pinguis were nearly identical, these potentially forming a single cryptic species complex. Four well-delineated genetic clades were identified, one of which included species of both Pavlova and Diacronema. Unique combinations of morphological/ultrastructural characters were identified for each of these clades. The ancestral pigment signature of the Pavlovophyceae consisted of a basic set of pigments plus MV chl cPAV, the latter being entirely absent in the Pavlova + Diacronema clade and supplemented by DV chl cPAV in part of the Exanthemachrysis clade. Based on this combination of characters, we propose a taxonomic revision of the class, with transfer of several Pavlova species to an emended Diacronema genus. The evolution of the class is discussed in the context of the phylogenetic reconstruction presented.Protist 06/2011; 162(5):738-61. DOI:10.1016/j.protis.2011.05.001 · 3.56 Impact Factor
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ABSTRACT: Pseudochattonella farcimen (Eikrem, Edvardsen, et Throndsen) is a unicellular alga belonging to the Dictyochophyceae (Heterokonta). It forms recurring blooms in Scandinavian coastal waters, and has been associated to fish mortality. Here we report the sequencing and analysis of 10,368 expressed sequence tags (ESTs) corresponding to 8,149 unique gene models from this species. Compared to EST libraries from other heterokonts, P. farcimen contains a high number of genes with functions related to cell communication and signaling. We found several genes encoding proteins related to fatty acid metabolism, including eight fatty acid desaturases and two phospholipase A2 genes. Three desaturases are highly similar to Δ4-desaturases from haptophytes. P. farcimen also possesses three putative polyketide synthases (PKSs), belonging to two different families. Some of these genes may have been acquired via horizontal gene transfer by a common ancestor of brown algae and dictyochophytes, together with genes involved in mannitol metabolism, which are also present in P. farcimen. Our findings may explain the unusual fatty acid profile previously observed in P. farcimen, and are discussed from an evolutionary perspective and in relation to the ichthyotoxicity of this alga.Protist 08/2011; 163(1):143-61. DOI:10.1016/j.protis.2011.07.004 · 3.56 Impact Factor