Analysis Of The Mitochondrial Genome Of Psettodes Erumei And Phylogenetic Analyses Of Flatfishes

Amplified the mitochondrial(mt) genome of P.erumei.The whole sequence was 17,315bp.It contained 22 transfer RNA genes(tRNA),2 ribosomal RNA genes (rRNA),13 protein-coding,genes,2 dominating non-coding regions.Most genes were encoded by the H-strand,except for ND6 and eight tRNA genes.Organization of P. erumei was the same as the typical vertebrate arrangement.Nucleotide composition in mtDNA genome of P.erumei were A 27.8%,T 23.9%,G 16.3%,C 2.1%,A+T 51.7%,a strong bias against the use of'G'.GC-skew =-0.32,AT-skew=0.08,which were typical in vertebrates.P.erumei mt genome protein-coding genes used ATG as the initiation codons with the only exception of COâ… and COâ…¢,which used GTG and CAC.Stop codons included TAA,TAG,TGG and incomplete stop codons T or TA.The base composition of Light-strand replication(O_L)exhibited unsimilarity to the corresponding region in the other flatfishes.The A+T of O_L of P.erumei was only 20.5%,this was much lower than 36.5%(Palichthys olivaceus) and other flatfishes(more than 50%).In flatfishes the secondary structure of O_L consisted of a conserve stem(TTCCC~*GCCT/ AAGGG~*CGGA) and loop structure.Designed two primer pairs L-Pro/HLOOP and eru21/CX4 divided control region into 5' end and 3' end.There were 56bp tandemly repeated sequence in the 5' end and 8bp tandemly repeated sequence in the 3'end respectively.The 5'end in eyes sinistral specimen had three different clongs,the number copies were 8.7,7.7,5.7.And 3'end has two different clongs,the number copie were 8 and 23.The control region in eyes dextra specimen had three kinds of clongs in 5'end,the number copies were 7.7;8.7;3.7,there were two clongs in 3'end,the number copies 6 and 25.It also exhibited the typical tripartite structure with a central domain and two adjacent variable domains(ETAS and CSB).All blocks of conserved sequences,TAS, CSB-D,E,F,CSB-1,2,3could be identified.The difference of base composition of complete CR sequences was greater than that of CR sequence excluding the repeated regions in nine species of flatfishes,and the variation coefficient of the former was about twice of the latter,which was mainly due to the sequences variation in base composition,length and copy numbers of repeated regions.Phylogenetic analysed of flatfishes with the Bayesian and ML method based on mtDNA genome(without CR) and CR.On both trees,P.erumei was the lowest group in the flatfishes,this was the same as morphological data.So maked sure evolutionary position of the P.erumei in flatfishes was very importantly to discuss the original of flatfishes in the future.At our level,the result considered that the hypothesis of monophyletic of flatfishes was stands,From our study it seemed to us that flatfishes's sister group was Carangidae(Perciformes-â… ) with a high bootstrap support value.