The Complete Sequence of the Mitochondrial Genome of the Chamberednautilus (Mollusca: Cephalopoda)
Background: Mitochondria contain small genomes that arephysically separate from those of nuclei. Their comparison serves as amodel system for understanding the processes of genome evolution.Although complete mitochondrial genome sequences have been reported formore than 600 animals, the taxonomic sampling is highly biased towardvertebrates and arthropods, leaving much of the diversity yetuncharacterized. Results: The mitochondrial genome of a cephalopodmollusk, the Chambered Nautilus, is 16,258 nts in length and 59.5 percentA+T, both values that are typical of animal mitochondrial genomes. Itcontains the 37 genes that are typical for animal mtDNAs, with 15 on oneDNA strand and 22 on the other. The arrangement of these genes can bederived from that of the distantly related Katharina tunicata (Mollusca:Polyplacophora) by a switch in position of two large blocks of genes andtranspositions of four tRNA genes. There is strong skew in thedistribution of nucleotides between the two strands. There are an unusualnumber of non-coding regions and their function, if any, is not known;however, several of these demark abrupt shifts in nucleotide skew,suggesting that they may play roles in transcription and/or replication.One of the non-coding regions contains multiple repeats of a tRNA-likesequence. Some of the tRNA genes appear to overlap on the same strand,but this could be resolved if the polycistron were cleaved at thebeginning of the downstream gene, followed by polyadenylation of theproduct of the upstream gene to form a fully paired structure.Conclusions: Nautilus sp. mtDNA contains an expected gene content thathas experienced few rearrangements since the evolutionary split betweencephalopods and polyplacophorans. It contains an unusual number ofnon-coding regions, especially considering that these otherwise often aregenerated by the same processes that produce gene rearrangements. Thisappears to be yet another case where polyadenylation of mitochondrialtRNAs restores what would otherwise bean incompletestructure.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director, Office of Science. Office of Biological andEnvironmental Research; National Science Foundation (NSF)
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 900782
- Report Number(s):
- LBNL-59181; R&D Project: Y00010; BnR: 600305000; TRN: US200711%%556
- Journal Information:
- BMC Genomics, Vol. 7, Issue 182; Related Information: Journal Publication Date: 07/19/2006
- Country of Publication:
- United States
- Language:
- English
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