Molecular Basis Of Adaptive Evolution Of The Eucryptorrhynchus Scrobiculatus And E.brandti

The Eucryptorrhynchus scrobiculatus and Eucryptorrhynchus brandti are two of the most important pests of the tree-of-heaven,Ailanthus altissima(Mill.),which can be found throughout China.Larvae of E.scrobiculatus feed on the root tissues of Ailanthus trees,thereby disrupting nutrient and water translocation,usually killing the trees in 3-5 years following initial attack.Furthermore,E.scrobiculatus and E.brandti,whose larvae feed on the phloem and cambial,respectively,often occur concurrently.The resource from the mitochondirla and transcriptome data should lay an important molecular foundation for future studies on adaptive evolution of the E.scrobiculatus and E.brandti.All the reaearch results are as follows.1.The complete mitochondrial genomes of E.scrobiculatus and E.brandtiComplete mtgenome sequences were obtained for E.scrobiculatus(15628bp)and E.brandti(15597bp).They are both circular and include the entire set of 36 genes usually present in animal mtDNA,including 13 PCG,21tRNA genes,2 ribosomal genes and A+T-rich region.In both mitochondrial genomes,the start codons for coxl and nadl are AAT and TTG,respectively.One striking feature is the deficiency of tRNA-Ile genes in two species.The complete sequences of AT-rich region have two regions including tandem repeats.2.Comparative mitogenomics of the ColeopteraMitochondrial gene order is usually conserved in Coleoptera which identical to the inferred ancestral gene complement for insect,but the deficiency of tRNA-Ile are common in Curculionidae.In the sequenced mitochondrial genomes of Coleoptera,the base composition has a significant AT bias.In the majority strand,species have a slight positive AT-skew(0.005-0.248)and an obvious negative GC-skew(-0.305--0.146).The ratio of the nonsynonymous substitution(Ka)and the synonymous(Ks)reflects the evolution of the motogenomes of the Coleoptera.In the 13 protein-coding genes of mitochondria,the Ka/Ks of nine genes are greater than 1 and the others are less than 1.Substitution saturation of coxl was analyzed by drawing transitions and transversions against genetic distance.With the increase of genetic distance,coxl gene nucleotide substitution tends to saturation,which provides phylogeetic informations will be inaccurate.3.Molecular phylogeny and divergence of the sympatric species E.scrobiculatus and E.brandtiBased on the molecular phylogeny,the phylogenetic position of Eucryptorrhynchus is inconsistent with the traditional classification.The Eucryptorrhynchus and Entiminae clustered into a clade,while the other species of Cryptorhynchinae formed the other clade.The divergence time of E.scrobiculatus and E.brandti can be traced back to about 3.76Ma the middle Pliocene(5.3-2.6 Ma).4.Transcriptomic analysis of E.scrobiculatusAn RNA pool obtained from E.scrobiculatus eggs,larva,pupae,and adults was sequenced and assembled de novo to obtain maximum diversity of sampled transcripts.A large number of molecular marker site were obtained from the transcriptome data,whichi could be used for the phylogeny study of the E.scrobiculatus and E.brandti.GO,KOG and KEGG anlyses provide the candidate genes associated with growth,reproduction,detoxification and stressful conditions of the E.scrobiculatus.