title: The Large Mitochondrial Genome of Symbiodinium minutum Reveals Conserved Noncoding Sequences between Dinoflagellates and Apicomplexans.
abstract: Even though mitochondrial genomes, which characterize eukaryotic cells, were first discovered more than 50 years ago, mitochondrial genomics remains an important topic in molecular biology and genome sciences. The Phylum Alveolata comprises three major groups (ciliates, apicomplexans, and dinoflagellates), the mitochondrial genomes of which have diverged widely. Even though the gene content of dinoflagellate mitochondrial genomes is reportedly comparable to that of apicomplexans, the highly fragmented and rearranged genome structures of dinoflagellates have frustrated whole genomic analysis. Consequently, noncoding sequences and gene arrangements of dinoflagellate mitochondrial genomes have not been well characterized. Here we report that the continuous assembled genome (∼326 kb) of the dinoflagellate, Symbiodinium minutum, is AT-rich (∼64.3%) and that it contains three protein-coding genes. Based upon in silico analysis, the remaining 99% of the genome comprises transcriptomic noncoding sequences. RNA edited sites and unique, possible start and stop codons clarify conserved regions among dinoflagellates. Our massive transcriptome analysis shows that almost all regions of the genome are transcribed, including 27 possible fragmented ribosomal RNA genes and 12 uncharacterized small RNAs that are similar to mitochondrial RNA genes of the malarial parasite, Plasmodium falciparum. Gene map comparisons show that gene order is only slightly conserved between S. minutum and P. falciparum. However, small RNAs and intergenic sequences share sequence similarities with P. falciparum, suggesting that the function of noncoding sequences has been preserved despite development of very different genome structures.
authors.affiliation: Marine Genomics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, Japan eiichi@oist.jp.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Shoguchi
authors.affiliation: Marine Genomics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, Japan.
authors.forename: Chuya
authors.initials: C
authors.lastname: Shinzato
authors.affiliation: Marine Genomics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, Japan.
authors.forename: Kanako
authors.initials: K
authors.lastname: Hisata
authors.affiliation: Marine Genomics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, Japan.
authors.forename: Nori
authors.initials: N
authors.lastname: Satoh
authors.affiliation: Marine Genomics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, Japan.
authors.forename: Sutada
authors.initials: S
authors.lastname: Mungpakdee
mesh_terms: D001483:Base Sequence; D002874:Chromosome Mapping; D017124:Conserved Sequence; D004141:Dinoflagellida / Q000235:genetics*; D023061:Gene Order; D059646:Genome Size; D054629:Genome, Mitochondrial; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000235:genetics*; D022661:RNA, Untranslated / Q000235:genetics; D059467:Transcriptome
chemical_list: D022661:RNA, Untranslated
keywords: Plasmodium; RNA editing; Symbiodinium; gene map; mitochondrial genome expansion; noncoding