Wc. Black et Rl. Roehrdanz, Mitochondrial gene order is not conserved in arthropods: Prostriate and metastriate tick mitochondrial genomes, MOL BIOL EV, 15(12), 1998, pp. 1772-1785
The entire mitochondrial genome was sequenced in a prostriate tick, Ixodes
hexagonus, and a metastriate tick, Rhipicephalus sanguineus. Both genomes e
ncode 22 tRNAs, 13 proteins, and two ribosomal RNAs. Prostriate ticks are b
asal members of Ixodidae and have the same gene order as Limulus polyphemus
. In contrast, in R. sanguineus a block of genes encoding NADH dehydrogenas
e subunit 1 (ND1), tRNA(Leu (UUR)), tRNA(Lett (CUN)), 16S rDNA, tRNA(Val),
12S rDNA, the control region, and the tRNA(Ile) and tRNA(Glm) have transloc
ated to a position between the tRNA(Glu) and tRNA(Phe) genes. The tRNA(Cys)
gene has translocated between the control region and the tRNA(Met) gene, a
nd the tRNA(Leu(CUN)) gene has translocated between the tRNA(Ser (UCN)) gen
e and the control region. Furthermore, the control region is duplicated, an
d both copies undergo concerted evolution. Primers that flank these rearran
gements confirm that this gene order is conserved in all metastriate ticks
examined. Correspondence analysis of amino acid and codon use in the two ti
cks and in nine other arthropod mitochondrial genomes indicate a strong bia
s in R. sanguineus towards amino acids encoded by AT-rich codons.