The Nile soft-shelled turtle, Trionyx triunguis, is a member of Trionychidae within Cryptodira and is considered the only extant species of its genus. The 16,590 base pairs (bp) mitochondrial genome (mtDNA) sequence of this species was determined in this study. It was found to have similar gene organization and base composition to that of most other vertebrates. Twenty-two tRNA genes, 2 rRNA genes, 13 protein-coding genes, and a control region were identified in this mtDNA. Similar to most turtle mtDNAs reported, an extra base was inserted at position 175 in the ND3 gene. This insertion could be processed by the translational frameshifting of the mRNA during protein synthesis or by RNA editing prior to translation. The control region was 1,078 bp long and it contained three conserved sequence blocks like most cryptodirans. Comparisons with three other soft-shelled turtles showed that the Trionyx triunguis control region contained a C-rich sequence at the 5' domain and twenty C (TA)3T-3' tandem repeat units at the 3' domain. This information could make soft-shelled turtles phylogeny being better understood. Preliminary survey of the genetic variation among Egyptian and Liberian individuals implied rather low gene diversity within species, calling the need for conservation of both the species and genetic biodiversity for Trionyx triunguis.
Key words: Trionychidae, mitochondrial genome, frameshift, control region
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