Induction Of Xenobiotics On Symbiotic Bacteria And The Genome Sequence In Cotton Aphid,Aphis Gossypii Glover

The cotton aphid(Aphis gossypii Glover),which belongs to Aphididae,Hemiptera,as a devastating insect pest,damages crops by sucking plant fluids and transmitting plant viruses.Cotton aphids are able to increase their population during a short period and then cause serious harm,due to their wide host range,strong adaptability,rapid reproduction and short generation time.These biology characteristics make cotton aphid become a promising model for the research of adaption.There are many kinds of symbiotic bacteria exist in cotton aphid,which play an important role in nutrient metabolism,development,reproduction and adaption.In the present study,the influences of four plant allelochemicals(tannic acid,gossypol,quercetin and 2-tridecanone)and an insecticide(omethoate)on symbiotic bacteria were investigated in cotton aphid.Besides,the whole genome of cotton aphid was sequenced to further explore the gene evolution and differentiation time.The results as follows:1.By mixing cotton aphid transcriptome,27,718 of 28,555 sequences were annotated.Among them,21%of annotated sequences were annotated as bacteria.Then combining with digital gene expression profiling data,the significant differential expressions of 68,63,52 and 151 genes were observed under the stress of 2-tridecanone,tannic acid,quercetin and gossypol,respectively.Most of the differential expression genes were up-regulated in the groups treated by 2-tridecanone and quercetin.While,most differential expression genes were down-regulated in the treatment groups by tannic acid and gossypol.The results by KEGG annotation showed that bacteria genes participated in many pathways,and mainly distributed in metabolism related pathways.2.The V3-V4 regions in 16S rDNA were sequenced in order to explore the changes of symbiotic bacteria species and abundance under the four plant allelochemicals stress.The results showed that most of the symbiotic bacteria were distributed in Actinobacteria,Firmicutes and Proteobacteria,and Proteobacteria account for more than 90%.The Buchnera was the dominant symbiotic bacteria in all of the samples,it's the proportion was 89.53%,83.03%,92.65%,91.33%and 54.61%in control,2-tridecanone,tannic acid,quercetin,and gossypol groups,respectively.In addition,the abundance of Serratia was significant decreased in the treatment group by 2-tridecanone while other secondary symbiotic bacteria appeared slightly increase.There was also obvious difference between gossypol treatment and control group:the abundance of Buchnera reduced,while the abundance of Serratia increased and the diversity of symbiotic bacteria enhanced.The differential species were also found in the groups treated by tannic acid and quercetin,meanwhile the whole community structure changed a little.3.According to the result of 16S rDNA sequencingin the cotton aphid,84 OTUs were generated by the stress of omethoat.The symbiotic bacteria also mainly distributed in Actinobacteria,Firmicutes and Proteobacteria on phylum level.Low dose of omethoat resulted in bacteria diversity descend,while only Buchnera abundance was increased.The diversity of symbiotic bacteria reduced slightly after the treatment by high dose of omethoat.However,the evenness of bacteria community risen,thus showed the system of bacteria tend to be more stable.Besides,the abundance of Buchnera declined under the stress of high dose of omethoat,while several multiple secondary symbiotic bacteria abundance rose significantly.4.Whole genome de novo sequence of cotton aphid was proceed by Illumina Hiseq 2500 and Pcibio RS ? platform.After quality control and data filter,557X second generation and 32X third generation data were generated.As cotton aphid genome possess a high heterozygosity,so we choose third generation sequence,which has 7,305 average reads length,to lower the heterozygosity pollution.We assembled the two platform sequencing data seperates,and then assembled into a high-quality result.As a result,the N50 of scaffolds was 1.05 Mb and N50 of contigs was 304 kb.The gene coverage reached 99%.5.59,640 repetitive sequences by the method of de novo prediction and homologous comparison were discovered in cotton aphid genome.The total size of repetitive region was 68 Mb accounting for 17.46%of whole genome.Structure prediction obtained 15,386 coding genes by de novo prediction,homologous comparison and combining published transcriptome data.Mapping with the public database,14,504 of homology genes were found,882 genes were exclusive in cotton aphid.In addition,we also obtained 92 microRNAs,102 snoRNAs,431 tRNAs and 596 rRNAs in the genome.6.Through comparative genomics method,we compared the genomes of cotton aphid with other sixteen spices genomes to analysis gene families and gene orthologys.The results indicated that cotton aphid genes were distributed into 8,006 gene families,in which 886 gene families were species-specific gene families for cotton aphid.Single-copy gene families were assembled to construct phylogenetic relationships.By estimating divergence times among lineages,we found that Hemiptera insect was diverged before 198.6(202.5-373.4)million years ago.Aphididae was diverged about 234.7(130.9-330.6)million years ago and the cotton aphid was diverged at 34.2(11.2-71.2)million years ago.7.Cotton aphid genomeis in a high quality of sequencing and assembling by comparing with Phis glycines,Myzus persicae,Diuraphis noxia and Acyrthosiphon pisum genomes.Then,xenobiotics adaption related gene familis were found in three aphid genomes with gene amplification and contraction.The gene pathways of xenobiotics adaption with KEGG database were established in three aphids.