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Complete sequence and gene organization of the mitochondrial genome of the land snail Albinaria coerulea.

ABSTRACT: The complete sequence (14,130 bp) of the mitochondrial DNA (mtDNA) of the land snail Albinaria coerulea was determined. It contains 13 protein, two rRNA and 22 tRNA genes. Twenty-four of these genes are encoded by one and 13 genes by the other strand. The gene arrangement shares almost no similarities with that of two other molluscs for which the complete gene content and arrangement are known, the bivalve Mytilus edulis and the chiton Katharina tunicata; the protein and rRNA gene order is similar to that of another terrestrial gastropod, Cepaea nemoralis. Unusual features include the following: (1) the absence of lengthy noncoding regions (there are only 141 intergenic nucleotides interspersed at different gene borders, the longest intergenic sequence being 42 nucleotides) (2) the presence of several overlapping genes (mostly tRNAs), (3) the presence of tRNA-like structures and other stem and loop structures within genes. An RNA editing system acting on tRNAs must necessarily be invoked for posttranscriptional extension of the overlapping tRNAs. Due to these features, and also because of the small size of its genes (e.g., it contains the smallest rRNA genes among the known coelomates), it is one of the most compact mitochondrial genomes known to date.

SUBMITTER: Hatzoglou E

PROVIDER: S-EPMC1206699 | biostudies-other | 1995 Aug

REPOSITORIES: biostudies-other

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Complete sequence and gene organization of the mitochondrial genome of the land snail Albinaria coerulea.

Hatzoglou E E Rodakis G C GC Lecanidou R R

Genetics 19950801 4

The complete sequence (14,130 bp) of the mitochondrial DNA (mtDNA) of the land snail Albinaria coerulea was determined. It contains 13 protein, two rRNA and 22 tRNA genes. Twenty-four of these genes are encoded by one and 13 genes by the other strand. The gene arrangement shares almost no similarities with that of two other molluscs for which the complete gene content and arrangement are known, the bivalve Mytilus edulis and the chiton Katharina tunicata; the protein and rRNA gene order is simil ...[more]

PMID: 7498775

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Project description:The complete sequence of honeybee (Apis mellifera) mitochondrial DNA is reported being 16,343 bp long in the strain sequenced. Relative to their positions in the Drosophila map, 11 of the tRNA genes are in altered positions, but the other genes and regions are in the same relative positions. Comparisons of the predicted protein sequences indicate that the honeybee mitochondrial genetic code is the same as that for Drosophila; but the anticodons of two tRNAs differ between these two insects. The base composition shows extreme bias, being 84.9% AT (cf. 78.6% in Drosophila yakuba). In protein-encoding genes, the AT bias is strongest at the third codon positions (which in some cases lack guanines altogether), and least in second codon positions. Multiple stepwise regression analysis of the predicted products of the protein-encoding genes shows a significant association between the numbers of occurrences of amino acids and %T in codon family, but not with the number of codons per codon family or other parameters associated with codon family base composition. Differences in amino acid abundances are apparent between the predicted Apis and Drosophila proteins, with a relative abundance in the Apis proteins of lysine and a relative deficiency of alanine. Drosophila alanine residues are as often replaced by serine as conserved in Apis. The differences in abundances between Drosophila and Apis are associated with %AT in the codon families, and the degree of divergence in amino acid composition between proteins correlates with the divergence in %AT at the second codon positions. Overall, transversions are about twice as abundant as transitions when comparing Drosophila and Apis protein-encoding genes, but this ratio varies between codon positions. Marked excesses of transitions over chance expectation are seen for the third positions of protein-coding genes and for the gene for the small subunit of ribosomal RNA. For the third codon positions the excess of transitions is adequately explained as due to the restriction of observable substitutions to transitions for conserved amino acids with two-codon families; the excess of transitions over expectation for the small ribosomal subunit suggests that the conservation of nucleotide size is favored by selection.

Dataset Information

Complete sequence and gene organization of the mitochondrial genome of the land snail Albinaria coerulea.

Publications

Complete sequence and gene organization of the mitochondrial genome of the land snail Albinaria coerulea.

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