Comparative and phylogenetic analysis of mitochondrial Cytochrome b gene and control region from natural triploid (Carassius auratus gibelio) in Chuzhou

The complete sequences of mitochondrial cytochrome b (Cyt b) gene and control region (D-loop) were amplified and sequenced in Carassius auratus gibelio, a natural triploid crucian carp in Chuzhou City of Anhui Province. No nucleotide variation sites were found in all sequences among 14 samples. The 1 141 bp Cyt b gene contained 29.2%, 27.8%, 28.5% and 14.5% of T, C, A and G, respectively; while 924 bp D-loop sequence contained 33.2%, 20.1%, 32.6% and 14.1% of T, C, A and G, respectively. The contents of A+T (57.5%, 65.8%) were significantly greater than those of G+C (42.3%, 34.2%) and G was the lowest among four nucleotides, the similar case as other aquatic animals. The key sequences of extended terminal associated sequences (ETAS), central domains (CSB-D, E and F) and conserved sequence blocks (CSB-1, CSB-2 and CSB-3) were identified. There was high sequence similarity between C.auratus gibelio in Chuzhou and other Carassius speciesrecorded in GenBank based on Cyt b (93%~100%) and D-loop (94%~99%) sequences, respectively. The phylogenetic trees constructed by NJ and MP methods based on the two sequences indicated that the closest phylogenetic relationship was between C.auratus gibelio in Chuzhou and that in Fangzheng, while the farthest one was between C.auratus gibelio in Chuzhou and crucian carps in Japan.