MITOCHONDRIAL GENOME SCAFFOLDS FROM three Labyrinthulomycete draft genome assemblies

COLLIER, JACKIE; BELIGNI, MV; AERTS, ANDREA; GRIGORIEV, IGOR; JENKINS, JERRY; KUO, ALAN; PANGILINAN, JASMYN

Banff, Alberta

Conferencia; Protist 2014: Conference of the International Society for Evolutionary Protistology and the International Society of Protistologists.; 2014

International Society for Evolutionary Protistology and the International Society of Protistologists.

Labyrinthulomycetes comprise ubiquitous, abundant, and diverse fungus-like marine protists. They are likely to play important roles in the decomposition of particulate organic matter in the oceans, including refractory substrates. They also produce, de novo, large amounts of essential polyunsaturated fatty acids, which may give them an important role in the nutrition of marine metazoans. To gain insight into the physiological ecology of these organisms, we are sequencing and annotating the genomes of Aplanochytrium sp. PBS07, Schizochytrium aggregatum ATCC 28209, and Aurantiochytrium limacinum ATCC MYA-1381. Among the assembled scaffolds we identified one from each organism consistent with mitochondrial genomes (mtDNA), and analyzed these in comparison to the previously reported mitochondrial genome from Thraustochytrium aureum (GenBank Accession AF288091). The Aurantiochytrium and Schizochytrium scaffolds were both similar in size to the gene-rich region of the Thraustochytrium mtDNA (34418, 36775, and 31570 bases, respectively). The Aplanochytrium mtDNA scaffold was much longer, 55616 bases, largely because of a repeat region containing several genes combined with greater intergenic spacing, not because of greater content of distinct genes. In fact, Aplanochyrium has transferred more genes from the mtDNA to the nuclear genome than the thraustochytrids. 21 tRNAs were identified in each of the three thraustochytrids, while 33 were identified in Aplanochytrium. Only one of the additional Aplanochytrium tRNAs was a type not present in the thraustochytrids, and the other 11 were duplicated in the repeat region. The Aplanochytrium scaffold also requires a unique genetic code to produce conserved proteins; in particular, TAG apparently encodes for tyrosine.