Taxonomic rearrangement of the genus Ulkenia sensu lato based on morphology, chemotaxonomical characteristics, and 18S rRNA gene phylogeny (Thraustochytriaceae, Labyrinthulomycetes): emendation for Ulkenia and erection of Botryochytrium, Parietichytrium, and Sicyoidochytrium gen. nov

Abstract

The genus Ulkenia is characterized by the naked protoplast stage within its life cycle. However, the 18S rRNA gene tree clearly shows that this genus is not a natural taxon, because our own isolates and reported strains separately form four well-supported monophyletic groups. These four groups are clearly distinguishable by their profi les of polyunsaturated fatty acids and carotenoid pigments and cell and colony morphology, e.g., persistence of sporangial wall, manner of the cell cleavage at the zoospore formation, and development of the ectoplasmic nets. Therefore, the four groups are assigned to four genera including three new genera, i.e., Ulkenia sensu stricto, Botryochytrium, Parietichytrium, and Sicyoidochytrium gen. nov.

Versatile Transformation System That Is Applicable to both Multiple Transgene Expression and Gene Targeting for Thraustochytrids

“…The phylogenetic analysis of thraustochytrids was performed on the basis of 18S ribosomal DNA sequences, as described previously (26,27), and four selected strains: Aurantiochytrium limacinum mh0186 (representative of the genus Aurantiochytrium) (19), Thraustochytrium aureum ATCC 34304 (Thraustochytrium), Parietichytrium sp. strain TA04Bb (Parietichytrium), and Schizochytrium sp.…”

“…However, the supply of fish oils is unstable due to declines in fish stocks, and thus, alternatives are required. One promising substitute for fish oils is thraustochytrids (class Labyrinchulomycetes, Stramenopiles) (2), unicellular eukaryotic marine protists, including those of the genera Aurantiochytrium (formerly known as the genus Schizochytrium), Parietichytrium, Schizochytrium sensu stricto, and Thraustochytrium (26,27). Thraustochytrids accumulate large amounts of DHA and n-6 docosapentaenoic acid (C 22:5n-6 ) mainly in their lipid droplets; however, they produce little EPA or arachidonic acid (C 20:4n-6 ) (5, 11).…”

Optimization of Culture Conditions for Growth and Docosahexaenoic Acid Production by a Marine Thraustochytrid, Aurantiochytrium limacinum mh0186

“…Nucleotide sequences were determined from both strands using the Big Dye Terminator Cycle Sequencing Kit (Applied Biosystems, Foster City, CA, USA) and ABI PRISM 3100 Genetic Analyzer (Applied Biosystems, Foster City, CA, USA) with previously described primers FA1, FA2, FA3, RA1, RA2, RA 13) , 18S001 and 18S13 12) . The obtained sequences were added to the aligned sequence data set 12,14) through a profile alignment process using ClustalW 15) and checked manually. Pairwise evolutionary distances were calculated following Kimura's 2-parameter (K2P) model 16) and were used to obtain a neighbor-joining (NJ) phylogenetic tree 17) with MEGA version 3.1 18) .…”

“…The quantities of individual fatty acids were estimated from the peak areas on the chromatogram using C19:0 fatty acid (nonadecanoic acid) as an internal standard. (accession number: DQ023620) 10,12,14) . Cell growth represented by OD660 under different carbon sources is shown in .…”

A Re-Visit to the Evolution and Ecophysiology of the Labyrinthulomycetes

“…2. A schematic summary of the phylogenetic relationships among the genera within the labyrinthulomycetes (modified from Tsui et al, 2009 andYokoyama et al, 2007b).…”