Studies On Genetic Differentiation Of Different Populations And Mitochondrial And Ribosomal Genome Of Aleurodicus Dispersus (Hemiptera:Aleyrodidae)

Aleurodicus dispersus Russell (Hemiptera:Aleyrodidae), also known as spiraling whitefly, has a high reproductive rate, short developmental phase and a wide range of host plants. As a result, rapid outbreaks are common and A. dispersus is targeted in quarantine in many countries in the world. In this study, the genetic differentiation of different populations of Aleurodicus dispersus was studied.The comlete mitochondrial and ribosomal DNA of Aleurodicus dispersus were analyzed. Meanwhile, the phylogenetic relationships among partial species of Hemiptera were reconstructed based on the complete mitochondrial and ribosomal genome sequences that are available in GenBank. This study could provid some basic data and experimental methods for the research of A. dispersus and Hemiptera. The results are as follows.1. Results from analysis of the mtDNA-COI gene and rDNA-ITS1gene of Aleurodicus dispersus showed that fairly low genetic variation existed among the different populations sampled in various locations. Analysis of the mtDNA-COI gene also showed that two haplotypes were found mid18samples in Hainan, with only the Wenchang sample coming from Psidium guajava L. carrying one variable position at the242-site in mtDNA-COI gene. In addition, Analysis of the rDNA-ITS1gene showed that the ITS1sequences of all the populations of Aleurodicus dispersus were consistent. There was no variable site in the ITS1gene. As the genetic distance between Taiwan population and Hainan population is very closeaccording our analysis, the invading Aleurodicus dispersus in Hainan, to some extent, is considered to be from Taiwan.2. In order to study the genetic differences of spiraling whitefly populations,16S gene of secondary endosymbiotic bacteria Cardinium, Arsenophonus and wsp gene of Wolbachia were studied in the present study. The results are as follows.1) Analysis of the16S gene of secondary endosymbiotic bacteria Cardinium and Arsenophonus showed that there were no variations existing among the different populations. Wolbachia infecting spiraling whitefly in Hainan, belonged to B group, and the phylogenesis of Wolbachia was in no positive correlation with the phylogenesis of spiraling whitefly.2) Both Cardinium and Arsenophonus could infect the spiraling whitefly of Hainan with high infection rate among43samples,with detection populations rate72.09%and93.02%respectively. Meanwhile, the detection sample size of Cardinium and Arsenophonus were93and120respectively, with the detection samples rate75.27%and87.50%accordingly.Although the spiraling whitefly could be infected by Cardinium and Arsenophonus with high detection samples rate, the detection population rate of Wolbachia infecting Aleurodicus dispersus was only2.32%with detection samples rate0.78%. 3. The complete mitochondrial DNA of Aleurodicus dispersus was sequenced, and the phylogenetic relationship of Hemiptera was reconstructed based on the complete mitochondrial genome sequences that are available in GenBank. Some conclusions drawn from the study are as follows.1) The mitogenome of A. dispersus was16170bp in length, including13protein-coding genes,20tRNA genes,2rRNA genes, and two A+T-rich regions. The nucleotide composition shows a high bias towards A+T.2) Most protein-coding genes of the studied A, dispersus started with a typical ATN codon. While the start codons of COI gene, COII gene, COIII gene were ATG, and ATP8gene, ND5gene were ATT. The TAA codon was used as the terminal codon for the most protein-coding genes, excepting COII gene, ND4gene and ND4L gene with incomplete codon T as their terminal codon. Phenylalanineare, leucine, isoleucine and asparagine were the most frequently used amino acids in the mitochondrial protein-coding genes.3) Besides tRNASer(AGN) lacking of dihydrouridine arm and the anticodon arm of tRNAAsn(N) with double loops, other tRNAs had typical secondary structures of clover leaf. The anticodons of most tRNAs were GNN and UNN, which were similar to those found in other Hexapoda animals. The aminoacyl stems and anticodon loops of tRNAs were conservative while other stems and loops were variable. The problem of inexact matching between some tRNA anticodons and high frequent synonymous codons can be solved by G-U pairing. The two rRNA genes were conservative.4) Phylogenomic analysis of mitochondrion were performed by the methods of neighbor joining, maximum parsimony, maximum likelihood and Bayesian inference based on combined gene data set(ALL data set)-protein-coding gene data set(PCG data set), rRNA data set and tRNA data set. The monophyly of Sternorrhyncha was supported, but monophyly of Auchenorrhyncha was not recovered in this study.4. The ribosomal DNA of Aleurodicus dispersus were sequenced, and the phylogenetic relationship of Hemiptera was reconstructed based on ribosomal genome sequences that are available in GenBank. Some conclusions drawn from the study are as follows.1) The secondary structure of18S rRNA was predicted according to the insect modal Drosophila melanogaster, and E21-5.6.7.8referred to Acyrthosiphon pisum. E41of SWF was predicted according to Plasmodium vivax(S gene).The secondary structure of E41of SWF was different from that of pea aphid, Acyrthosiphon pisum, because of the different model used. If the E41structure of Aleurodicus dispersus was peculiar, we need to make a deeper study.2) The monophyly and5suborders of Hemiptera have been supported by the analysis of three ribosomal gene data sets (18S rDNA, ITS1-5.8S-ITS2rDNA, and28S rDNA), especially for18S rDNA gene data sets. The five suborders were Sternorrhyncha, Cicadorrhyncha, Fulgororrhyncha, Coleorrhyncha and Heteroptera.