The Mitochondrial Genome Of Symphysodon Discus Heckel And Its Comparative Analysis To Other Four Breeding Varieties In Cytb And 5S RDNA

Symphysodon discus Heckel is a cichlid(Perciformes: Cichlidae). The beautiful fish is native to the amazon basin and has an important status in the aquaculture. After a longtime breeding, a lot of varieties with different colors and patterns on body have been formed. More and more people have great interest on the relationship of colorful wild species and varieties of artificial breeding, which is right the main objective of this study.This research sequenced the complete mitochondrial genome of wild Heckel Discus.And the gene of Cytb of four kinds of breeding varieties( Red Spotted Green Discus, Solid Red Discus, Pigeon Blood Discus and Royal Blue Discus) were studied and compared with Heckel’s Cytb gene. Moreover, 5S r DNA of these five discus species were compared and analyzed for their genetic relationships.1. Mitochondrial genome of Heckel DiscusDNA was extracted from fins of Heckel Discus, augmented by PCR amplification technology, and joined together for the whole mitochondrial genome sequence of Heckel Discus. The whole length of genome sequence was 16544 bp including 22 t RNA genes, 13 coding protein, 2r RNA genes and non-coding regions.The content of basic group A, G, C and T in the whole genome sequence was 28.86%,14.96%, 30.15% and 14.96%, respectively. There were two kinds of initiation codon ATG and GTG in protein genome, while there werethree kinds of termination codon TAA, TAG and an incomplete termination codon T--. There were eight genetic overlap area and 12 genetic interval area of the whole mitochondrial genome.2. Comparative analysis in Cytb gene of Heckel and four breeding discus varietiesDNA of Red Spotted Green Discus, Solid Red Discus, Pigeon Blood Discus and Royal Blue Discus were extracted and their Cytb genome sequences were obtained by PCR amplification technology. The Cytb gene sequence length was 1137 bp consistent with Heckel’s discus. Homology comparison and base composition were analyzed by MEGA5.0 software. Then it was concluded that the content of bases A +T was higher than G + C. The initiation codon and termination codon of these five discus were all ATG and TAA, respectively. The homology of Pigeon Blood Discus,Red Spotted Green Discus, Royal Blue Discus and Solid Red Discus was respectively97.27%, 97.27%, 98.86% and 97.27% compared with Heckel’s Discus.3. Sequence analysis of 5S r DNA among five discus fish SymphysodonThe 5S r DNA was extracted and sequenced in fin raysfrom the five discus fish Symphysodon by designed primers. The results showed that the five discus all had the structural unit in 5Sr DNA of 201 bp and 410 bp. However, the structural units of 300 bp,299bp and 338 bp with high conservative coding regions were observed in the Heckel Discus(the wild one), Solid Red Discus and Pigeon Blood Discus. There was significant difference in non-transcribed spacer regions, especially the 300 bp in Heckel Discus(wild), the 299 bp in Solid Red Discus and the 338 bp in Pigeon Blood Discus. There was very high G+C base content in these discus. The wild Heckel Discus showed genetic relationship rate of 97.53% with Red Spotted Green Discus,90.12% with Solid Red Discus, 88.89% with Pigeon Blood Discus and 85.19% with Royal Blue Discus, meaning the maximal genetic relationship rate in Red Spotted Green Discus.