Variation and evolution of polyadenylation profiles in sauropsid mitochondrial mRNAs as deduced from the high-throughput RNA sequencing

Background Genes encoded in vertebrate mitochondrial DNAs are transcribed as a polycistronic transcript for both strands, which is later processed into individual mRNAs, rRNAs and tRNAs, followed by modifications, such as polyadenylation at the 3′ end of mRNAs. Although mechanisms of the mitochondrial transcription and RNA processing have been extensively studied using some model organisms, structural variability of mitochondrial mRNAs across different groups of vertebrates is poorly understood. We conducted the high-throughput RNA sequencing to identify major polyadenylation sites for mitochondrial mRNAs in the Japanese grass lizard, Takydromus tachydromoides and compared the polyadenylation profiles with those identified similarly for 23 tetrapod species, featuring sauropsid taxa (reptiles and birds).