| The Asian citrus psyllid,Diaphorina citri Kuwayama(Hemiptera: Psylloidea)is recorded to cause extensive damage to the plants of Rutaceae families,for the adult and nymph suck the plant juices and has distributed all over the world.The Asian citrus is the most important pest as the vector of Huanglongbing(HLB),the citrus greening disease.D.citri is mainly distributed in the citrus production areas,and has serious damaged to citrus industries in south China.There are no efficient control methods for the HLB,for the citrus psyllid is the mainly vector of HLB in the field,therefore the prevention and treatment of citrus psyllid occurred to be an effective way to prevent the spread of HLB.In this study,the complete mitochondrial genome of D.citri has been sequenced and annotated,and a comparative analysis is provided with known Psylloidea species.The phylogenetic relationships among Sternorrhyncha species were reconstructed based on the complete mitochondrial genome sequence that are available in GenBank.Additionally,to determine genetic variation among geographic population of D.citri,mitochondrial gene cytochrome oxidase I(mtCOI)was used to characterize China populations.Phylogenetic analyses were utilized to elucidate the relationship among the sequence data in this study and all mtCOI sequence available in public.And then provides the genetic basis for the effective biological control agents of D.citri.The main results of this study are as follows:(1)The complete mitochondrial genome of D.citri has been sequenced,annotated and analyzed(GenBank: KX073968).The complete mitochondrial genome of D.citri is a typical circular molecular of 15038 bp in length with an A+T content of74.56%,and contains 13 protein-coding genes(PCGs),22 tRNA genes,2 rRNA genes and a large non-coding region(control region).The mitochondrial genome has several features: The gene order is identical to the ancestral arthropod mitochondrial gene order,and All PCGs use standard initiation codons(ATN),and stop with TAA and TAG except ND2 and ND5 which stop with incomplete termination codon T.All tRNA genes(54~70 bp)have the typical clover-leaf structure,with the exception of trnS1 lacking the dihydrouridine(DHU)arm.The control region is located between rrnL and the trnI gene with the highest A+T content of all regions.(2)Comparative analysis within five Psylloidea species D.citri,Cacopsyllacoccinea,Pachypsylla venusta,Bactericera cockerelli and Paratrioza sinica suggested: the mitochondrial genomes of five psyllids are contain 37 genes typical found in most metazoans.The mitochondrial genomes of five psyllids have the same gene order and similarly high A+T content.The PCGs have strong codon usage bias and the A+T content at the third codon position,which is higher than that at the first and second codon position.The tRNA genes found in the five psyllids were the same with all tRNA genes have the typical clover-leaf structure,except trnS1 lacking the dihydrouridine(DHU)arm.The evolutionary rate of protein-coding genes indicated that the cytochrome oxidase subunits I(COI)have the slowest evolutionary rate therefore COI sequence diversity can be used as a DNA barcoding to identify closely related species.By contrast,ATP8 has the highest evolutionary rate which can be used as a effective molecular marker to analyze intraspecific relationships and reveal the relationship among different populations within the same Psylloidea species.(3)The phylogenic relationships of 23 Sternorrhyncha species have been reconstructed.The maximum likelihood(ML)and Bayesian inference(BI)based on nucleotide sequences of 13 PCGs or/and 2 rRNAs,and the ML and MP trees based on amino acid sequences of 13 PCGs supported the traditional morphological classification.(4)119 D.citri individuals of 23 different geographic populations from China and one population from Florida were sampled.The mitochondrial COI gene fragments were amplified and sequenced from all samples.The aligned consensus COI fragment was 721 bases long and 10 haplotypes based on the COI gene were detected.Haplotype analysis indicates that Hap1 is the preponderant haplotype shared with all geographic populations of China.The genetic diversity and haplotype diversity were relatively low,moreover there were no genetic diversity for the Ganzhou sampled populations.(5)The genetic distance between the various groups are smaller in our country,the small genetic differences between populations and the geographic almost no significant genetic differentiation between populations.The population according to the geographical position is divided into two groups of AMOVA analysis indicates that population within the genetic variation of total variation respectively,mainly from genetic variation within a population.Spatial structure analysis showes no significant correlation between geographic distance and genetic distance.(6)The phylogenetic analyses showed that D.ctiri in China,Vietnam,Thailand,Indonesia,Mauritius Island and Reunion Island are similar belong to the South East group.These result should be considered when looking for biological control. |
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