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| Gene Order,Characteristics and Phylogenetic Analyses of Mitochondrial Genomes in Flatfish Pleuronectiformes |
| SHEN Xin,TIAN Mei,MENG Xueping,CHENG Hanliang,XU Jianhe,YAN Binlun |
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Abstract T he gene content of mitochondrial genomes is highly conserved (each encoding 37 genes ) in flatfish Pleuronectiformes .The A + T contents of mitochondrial main coding strands from the suborder Pleuronectoidei ,ranging between 53 .21% (starry flounder Platichthys stellatus ) and 55 .78% (turbot Scophthalmus maximus ) , were lower than those from the suborder Soleoidei . The maximal A + T contents were observed in family Cynoglossidae of suborder Soleoidei ,60 .35% in shortnose tongue-sole Cynoglossus abbreviatus and 60 .59% in half-smooth tongue-sole C .semilaevis .However ,the A + T content from the family Soleidae of suborder Soleoidei (54 .63% in Senegalese sole Solea senegalensis) was found very similar to those of suborder Pleuronectoidei .The ratios of synonymous substitution (K a) to synonymous substitutions (Ks) (K a/Ks) in mitochondrial protein-coding genes were ranged from 0 to 0 .2171 in Hippoglossus ,Verasper and Cynoglossus ,indicating that there is a strong purification (negative) selection in Pleuronectiformes mitochondrial genomes . The comprehensive analysis of 12 Pleuronectiformes mitochondrial gene mutation features show s that nad5 ,nad4 and nad2 genes are ideal molecular markers . Mitochondrial gene order of nine species from the suborder Pleuronectoidei and Senegalese sole from the family Soleidae in suborder Soleoidei is a typical arrangement of vertebrate mitochondrial genomes . However , there are translocation and inversion of tRNA gene (trnQ ) in mitochondrial genomes of shortnose tongue-sole and half-smooth tongue-sole from the family Cynoglossidae of suborder Soleoidei . Mitochondrial genome data support the phylogenetic relationship within Pleuronectiformes at families level : [(Pleuronectidae+ Paralichthyidae)+ Scophthalmidae)]+ Soleidae) + Cynoglossidae . The family Soleidae of suborder Soleoidei was clustered with the suborder Pleuronectoidei firstly (BPN = 100 , BPM = 100) ,followed by clustered with the family Cynoglossidae (BPN = 100 ,BPM = 100) ,indicating that there are two clades in the suborder Soleoidei .Integrated other genomic features ,including A + T content and gene order ,Soleoidei is considered as monophyletic group being questioned ,and need further study .
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Received: 25 October 2013
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