Study On Mitochondrial Genome Structure And Phylogeny Of Seven Staghorn Corals(Scleractinia:Acroporidae)

Coral reefs,one of the most important resources,have been in decline since the1990s.This article aims to provide data and theoretical basis for coral classification and coral reef ecosystem protection by analyzing the mitochondrial genome structure and phylogeny of seven Acroporidae species.We got seven corals in Sanya.They are Acropora digitifera,Acropora microphthalma,Acropora intermedia,Montipora digitate,Acropora hyacinthus,Montipora vietnamensis and Montipora monasteriata.The main research results are as follows:The complete sequence length of mitochondrial genome of seven Acroporidae species ranges from 17690 bp to 18360 bp,including two rRNA genes,two tRNA genes and thirteen protein-coding genes.The base composition is T>A>G>C,showing high AT content.They contain 13 protein-coding genes:ND1,ND2,ND3,ND4,ND4L,ND5,ND6,COI,COII,COIII,Cytb,ATP6 and ATP8,coding in H chain.The sequence and composition are consistent.The length of tRNA^Metet is 71 bp,and tRNA^Trp is 70 bp.All of them form stable stem loop structures.12S rRNA and 16S rRNA are relatively conservative and fixed,both located in the H chain.The substitutions at three codon positions of the mitochondrial protein gene sequences are not saturated.In the study of phylogenetic relationships,the data of Acropora hyacinthus and Acropora microphthalma are the same with the results in the GenBank.The data of Acropora digitifera and Acropora intermedia are different from the results in the GenBank.Both of their genetic distances are 0.00076.Montipora digitate,Montipora vietnamensis,Montipora monasteriata are the closest genetic relatives to Montipora peltiformis.Their genetic distances are 0.00034,0.00279,0.00102.The results show that the mitochondrial genome sequence can clearly express the taxonomic status and phylogenetic relationships among corals of different genera.The complete sequences of mitochondrial genome are difficult to clearly distinguish the differences among different species of the same genus,which need to be further proved by combining traditional morphological classification and partial nuclear gene fragments.