Characterization Of Three Complete Mitochondrial Genome From Different Family Of Lepidopteran

Mitochondrial DNA(mtDNA)is maternally inherited DNA,characterized by a rapid evolutionary rate and lack of genetic recombination.It has been widely used as an informative molecular marker for diverse evolutionary studies among species,including molecular evolution,phylogenetics,population genetics,and comparative and evolutionary genomics.Lepidoptera is large,accounting for more than 140,000 insect species,but only about 700 complete or near-complete mitogenomes are currently available in GenBank.In order to enrich the Lepidoptera mitogenome data,and go further into structural and evolutionary studies of the mitogenome in Lepidoptera insect,mitogenomes of three Lepidoptera species,Cerura menciana,Agrius convolvuli,Eligma narcissus belonging to three families were sequenced,assembled,annotated and anylazed.Then these mitogenomes combined with other Lepidoptera species which deposited in GenBank used to conduct a comprehensive comparative analysis including the length,the base composition,the protein coding genes,the transfer RNA,condon usage and control regions.In addition,the phylogenetic relationships among lepidoptera insects were reconstructed and analyzed based on the nucleotide sequences of the 13 PCGs from other insect mitogenomes.The studies and the main results are as followings:1.The complete mitogenome of C.menciana was found to be a closer circular molecules of 15,369 bp in size,the A.convolvuli mitogenome was 15,349 bp and the complete mitogenome of E.narcissus was determined to be 15,329 bp.All of these mitogenomes contained 37 genes including 13 protein-coding genes(PCGs: seven NADH dehydrogenase subunits [nad1-nad6 and nad4L],three cytochrome c oxidase subunits [cox1-cox3],two ATPase subunits [atp6 and atp8],one cytochrome b [cob],two ribosomal RNA genes [rrn L and rrnS]),and 22 transfer RNA(tRNA)genes.2.The nucleotide compositions of mitgenomes of C.menciana,A.convolvuli and E.narcissus were biased toward adenine and thymine.The GC skew was negative.The A+T content of C.menciana,A.convolvuli and E.narcissus was 80.06%,81.49% and 81.00%,respectively.3.All the PCGs of C.menciana,A.convolvuli and E.narcissus mitgenomes were started with the canonical putative start codons ATN except for the cox1 gene which uses CGA instead.In addition,most PCGs share complete termination codon TAA and TAG,and the other genes use incomplete stop codons(single T).4.The structures of all the 22 tRNAs from C.menciana,A.convolvuli and E.narcissus mitgenomes were similar to other lepidoptera.The length of the tRNA genes various from 64 bp to 73 bp.All the tRNAs of C.menciana and A.convolvuli could be folded into the expected secondary cloverleaf structures except the trnS1,in which its dihydrouridine(DHU)arm simply forms a loop,whereas all the 22 tRNAs from E.narcissus could be folded into the expected secondary cloverleaf structures.5.There were obvious biases in the both codon and amino acid usage in these Lepidoptera species.The codons of high content of G and C were abandoned appears in C.menciana,A.convolvuli and E.narcissus.The results of the codon usage of these three mitogenomes indicted that Asn,Ile,Leu2,Tyr and Phe were the five most frequent amino acids.6.The A+T-rich region is located between the rrnS and trnM genes,The length of A+T-rich region of C.menciana,A.convolvuli and E.narcissus was 372 bp,331 bp and 434 bp,respectively.The AT content of A+T-rich region of C.menciana,A.convolvuli and E.narcissus was 94.35%,93.35%,96.54%,respectively.7.The phylogenetic relationships among the seven superfamilies of lepidopteran were reconstructed based on concatenated nucleotide sequences of the 13 PCGs using Maximum Likelihood method All the results supported a close relationship between the Noctuoidea,Bombycoidea and Pyraloidea.This result deviated from the traditional view.To confirm these relationships,more advanced studies based on massive samples need to be performed.This work was the first report about the complete mitogenome sequence of C.menciana,A.convolvuli and E.narcissus.It could provide some references during futher research.