Complete mitochondrial genome of Rectorisluxiensis (Teleostei, Cyprinidae): characterisation and phylogenetic...

Mitochondrial genomes (mitogenomes) are widely used in scientific studies on phylogenetic relationships, molecular evolution and population genetics. Here, we sequenced and analysed the mitogenome of Rectorisluxiensis, a Yangtze River drainage endemic, but threatened cyprinid fish of Labeoninae. The complete mitogenome of R.luxiensis was 16,592 bp in length, encoding 13 protein coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs) and a control region. The mitogenome showed a high A+T content (58.2%) and a positive AT-skew (0.10) and negative GC-skew (-0.25) base composition pattern. All the 13 PCGs were found to start with ATG codons, except for the COXI, in which GTG was the start codon. The ratio of non-synonymous and synonymous substitutions (Ka/Ks) of all the 13 PCGs were less than 1, indicating negative or purifying selection evolved in these genes. Comparatively speaking, the evolutionary rate of ATP8 was the fastest and ND4L was the slowest. All tRNAs could fold into a typical cloverleaf secondary structure, except tRNA^Ser1 that lacked a dihydrouridine arm. Phylogenetic relationships, based on the PCGs dataset of 91 mitogenomes of Labeoninae, showed that R.luxiensis grouped with Rectorisposehensis and they formed a monophyletic Rectoris. However, many non-monophyletic genera were revealed in labeoninae fishes, such as Cirrhinus, Decorus, Garra, Labeo and Pseudocrossocheilus, which indicated that the validities of some traditional genera required a further check. This study reported the complete mitogenome of R.luxiensis for the first time, which provided valuable data for future molecular evolution and conservation related studies of Rectoris and other species in Labeoninae.