Dataset Information

The mitochondrial genome of the brachiopod Laqueus rubellus.

ABSTRACT: The complete nucleotide sequence of the 14,017-bp mitochondrial (mt) genome of the articulate brachiopod Laqueus rubellus is presented. Being one of the smallest of known mt genomes, it has an extremely compact gene organization. While the same 13 polypeptides, two rRNAs, and 22 tRNAs are encoded as in most other animal mtDNAs, lengthy noncoding regions are absent, with the longest apparent intergenic sequence being 54 bp in length. Gene-end sequence overlaps are prevalent, and several stop codons are abbreviated. The genes are generally shorter, and three of the protein-coding genes are the shortest among known homologues. All of the tRNA genes indicate size reduction in either or both of the putative TPsiC and DHU arms compared with standard tRNAs. Possession of a TV (TPsiC arm-variable loop) replacement loop is inferred for tRNA(R) and tRNA(L-tag). The DHU arm appears to be unpaired not only in tRNA(S-tct) and tRNA(S-tga), but also in tRNA(C), tRNA(I), and tRNA(T), a novel condition. All the genes are encoded in the same DNA strand, which has a base composition rich in thymine and guanine. The genome has an overall gene arrangement drastically different from that of any other organisms so far reported, but contains several short segments, composed of 2-3 genes, which are found in other mt genomes. Combined cooccurrence of such gene assortments indicates that the Laqueus mt genome is similar to the annelid Lumbricus, the mollusc Katharina, and the octocoral Sarcophyton mt genomes, each with statistical significance. Widely accepted schemes of metazoan phylogeny suggest that the similarity with the octocoral could have arisen through a process of convergent evolution, while it appears likely that the similarities with the annelid and the mollusc reflect phylogenetic relationships.

SUBMITTER: Noguchi Y

PROVIDER: S-EPMC1461069 | biostudies-other | 2000 May

REPOSITORIES: biostudies-other

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The mitochondrial genome of the brachiopod Laqueus rubellus.

Noguchi Y Y Endo K K Tajima F F Ueshima R R

Genetics 20000501 1

The complete nucleotide sequence of the 14,017-bp mitochondrial (mt) genome of the articulate brachiopod Laqueus rubellus is presented. Being one of the smallest of known mt genomes, it has an extremely compact gene organization. While the same 13 polypeptides, two rRNAs, and 22 tRNAs are encoded as in most other animal mtDNAs, lengthy noncoding regions are absent, with the longest apparent intergenic sequence being 54 bp in length. Gene-end sequence overlaps are prevalent, and several stop codo ...[more]

PMID: 10790399

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Project description:Background:Hox genes encode a family of homeodomain containing transcription factors that are clustered together on chromosomes of many Bilateria. Some bilaterian lineages express these genes during embryogenesis in spatial and/or temporal order according to their arrangement in the cluster, a phenomenon referred to as collinearity. Expression of Hox genes is well studied during embryonic and larval development of numerous species; however, relatively few studies focus on the comparison of pre- and postmetamorphic expression of Hox genes in animals with biphasic life cycle. Recently, the expression of Hox genes was described for embryos and larvae of Terebratalia transversa, a rhynchonelliformean brachiopod, which possesses distinct metamorphosis from planktonic larvae to sessile juveniles. During premetamorphic development, T. transversa does not exhibit spatial collinearity and several of its Hox genes are recruited for the morphogenesis of novel structures. In our study, we determined the expression of Hox genes in postmetamorphic juveniles of T. transversa in order to examine metamorphosis-related changes of expression patterns and to test whether Hox genes are expressed in the spatially collinear way in the postmetamorphic juveniles. Results:Hox genes are expressed in a spatially non-collinear manner in juveniles, generally showing similar patterns as ones observed in competent larvae: genes labial and post1 are expressed in chaetae-related structures, sex combs reduced in the shell-forming epithelium, whereas lox5 and lox4 in dorso-posterior epidermis. After metamorphosis, expression of genes proboscipedia, hox3, deformed and antennapedia becomes restricted to, respectively, shell musculature, prospective hinge rudiments and pedicle musculature and epidermis. Conclusions:All developmental stages of T. transversa, including postmetamorphic juveniles, exhibit a spatial non-collinear Hox genes expression with only minor changes observed between pre- and postmetamorphic stages. Our results are concordant with morphological observation that metamorphosis in rhynchonelliformean brachiopods, despite being rapid, is rather gradual. The most drastic changes in Hox gene expression patterns observed during metamorphosis could be explained by the inversion of the mantle lobe, which relocates some of the more posterior larval structures into the anterior edge of the juveniles. Co-option of Hox genes for the morphogenesis of novel structures is even more pronounced in postmetamorphic brachiopods when compared to larvae.

Dataset Information

The mitochondrial genome of the brachiopod Laqueus rubellus.

Publications

The mitochondrial genome of the brachiopod Laqueus rubellus.

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