The complete mitochondrial DNA (mtDNA) sequence of the brine shrimp Artemia franciscana has been determined. It extends the present knowledge of mitochondrial genomes to the crustacean class and supplies molecular markers for future comparative studies in this large branch of the arthropod phylum. Artemia mtDNA is 15,822 nucleotides long, and when compared with its Drosophila counterpart, it shows very few gene rearrangements, merely affecting two tRNAs placed 3' downstream of the ND 2 gene. In this position a stem-loop secondary structure with characteristics similar to the vertebrate mtDNA L-strand origin of replication is found. This suggests that, associated with tRNA changes, the diversification of the mitochondrial genome from an ancestor common to crustacea and insects could be explained by errors in the mtDNA replication process. Although the gene content is the same as in most animal mtDNAs, the sizes of the protein coding genes are in some cases considerably smaller. Artemia mtDNA uses the same genetic code as found in insects, ATN and GTG are used as initiation codons, and several genes end in incomplete T or TA codons.

No abstract

To extend to the crustacean class the information concerning the genomic organization of the mitochondrial DNA (mtDNA) a double strategy has been used: Southern blot analysis with cloned Drosophila mtDNA probes and sequence comparison to the Drosophila mtDNA of the sequenced termini of different subclones along the Artemia mitochondrial genome, probably the smallest mtDNA studied at this level to date. These approaches have allowed us to localize the 16S rRNA gene, two tRNA genes and eleven protein genes. The genome organization is surprisingly similar to the Drosophila mtDNA, with the 16S rRNA and the protein genes located in the same positions and orientations as their Drosophila counterparts. The only changes detected are at the level of tRNA genes, although the position and orientation of some of these are also conserved. These results contrast with the important rearrangements detected among other invertebrates mtDNAs and suggest that the genome organization of the mitochondrial DNA may be more conserved in the arthropods than in other invertebrate phyla.

No abstract

No abstract