Comparative mitochondrial genomes and proteomes of three osmoheterotrophic marine protists (labyrinthulomycete)

COLLIER, JACKIE; BELIGNI, MV

Encuentro; ASCB/EMBO 2018 Meeting; 2018

The American Society for Cell Biology

Labyrinthulomycetes are ubiquitous, abundant, and diverse fungus-like marine protists, likely to play important roles in the decomposition of particulate organic matter in the oceans. 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 cell biology of these organisms, we are using the draft genome sequences of one aplanochytrid, Aplanochytrium sp. PBS07, and two thraustochytrids, Schizochytrium aggregatum ATCC 28209 and Aurantiochytrium limacinum ATCC MYA-1381, to characterize their mitochondrial proteomes, including the mitochondrial genomes (mtDNA) as well as nuclear-encoded proteins with probable mitochondrial localization. Each of these JGI genome sequencing projects produced a scaffold consistent with a mtDNA. The Aurantiochytrium and Schizochytrium scaffolds were both similar in size to the gene-rich region of the previously reported mitochondrial genome from the thraustochytrid Thraustochytrium aureum (GenBank Accession AF288091) and recently from ?Schizochytrium? TIO1101 (GenBank Accession KU183024). The Aplanochytrium mtDNA scaffold was longer largely because of longer genes and greater intergenic spacing, not because of greater gene content. In fact, the Aplanochytrium mtDNA lacked several genes found in all three thraustochytrids (including nad7, nad9, and nad11). Aplanochytrium did contain one tRNA not present in thraustochytrid mtDNA: a trnX(cua), apparently modified from a trnY(gua), which we predict allows TAG codons to encode tyrosine rather than stop. As reported for Thraustochytrium aureum, Nanopore sequencing suggests that the Aurantiochytrium mtDNA is circular with a repetitive, noncoding region of similar size as the gene-rich region.