| Aphids(Aphidoidea)is a kind of multi-feeding insect.As a result of wide range of feeding,there are many kinds of plants that can be fed,so they can differentiate on the selection of species that can be eaten.After a long period of evolution,there is a dependence and specificity on a host,that is,host specialization.On the basis of the pea aphid(Acyrthosiphon piusm Harris),Myzus persicae(Sulzer)and corn aphid(Rhopalosiphum maidis)having a host biotypes phenomenon,and host biotypes phenomenon about cotton aphid(A.gossypii Glover)have been reported in Xinjiang,Nanjing,Henan and other places,combined with Yangzhou area presenting a vegetation diversity phenomenon,that many ornamental plants will become the place for the cotton aphid to spend winter,and migration to cotton and cucumber to feed plant leaf when spring coming,therefore this thesis begins from the second host plant,that aphid living conditions to explore different situation researching on host differentiation in Yangzhou region,and with the help of the difference in gene expression of transcriptome sequencing technology of different host group of cotton aphid,to find host specific genes related to type,and provide a theoretical basis for the application of targeted prevention and control technology of cotton aphid.Therefore,this paper selects three plants(cotton,cucumber and squash)as hosts to raise cotton aphid,the results are as follows:1.Mutual transfer cotton aphid between cotton,cucumber and zucchini to establish population life table for studying on differentiation of cotton aphid,experimental results show:Only eighth,ninth and tenth days have a calving phenomenonwhen after the cotton aphid living in cotton transferred to cucumber,and net reproductive rate(R0)decreased significantly,and intrinsic growth rate(Rm)was negative,therefore come to conclusion that population can not be established when the cotton aphid living in cotton transferred to cucumber;After the cotton aphid living in cucumber transferred to cotton five days,the average survival rate of first five days is only 39.67%,and the average litter size is only 0.24 aphid per day,intrinsic growth rate decreased significantly,therefore,the cotton aphid living in cucumber is difficult to establish population in cotton;After the cotton aphid living in pumpkin transfer to other two host plants(cotton,cucumber)five days,the average survival rates were 85.31%and 91.01%,and rm>0,R0>1,compared with the other two groups,the cotton aphid living in pumpkin had no significant difference.The study pointed out that the cotton and cucumber aphid mutualing transfer can not establish normal population,zucchini group aphid comparing with the other two groups had no differentiation phenomenon.Results show that the cotton aphid living in Yangzhou region can be divided into cotton and cucumber type.2.Sequencing gene expression of the cotton aphid by transcriptome sequencing technology.Results show that:The expression density distribution of the aphid gossypii living in the three host plant indicate that the gene concentrated area enrichment a large number of differentially expressed genes between cotton and pumpkin group,squash group is located between the two groups;the number of different genes of cotton aphid between living in cucumber and cotton is far more than compared with the aphid living in squash(P<0.01、P<0.05).This shows that the differences between cucumber and cotton group is greater than the zucchini and cotton group;Obtained by Venn diagram,there were 8260 differentially expressed genes between the cotton and cucumber groups,and there were 1106 differentially expressed genes compared with the squash group,and there were 276 differentially expressed genes in cucumber and zucchini group.The number of differentially expressed genes between cotton and cucumber was 7.5 times as high as that of Zucchini group,and the difference between the number of genes in Cucumber group and zucchini group was about 30 times higher than that of the group;Compared with the GO database,it was found that the differentially expressed genes were mainly concentrated in the metabolic process,cell process,biochemical process regulation,cell components,and the activity of the catalyst.3.Seven kinds of enzymes was screened based on the results of transcriptome,they are respectively cytochrome(P450)、acetylcholinesterase(AchE)、glutathione-S-transferase(GST)、NADH dehydrogenase complex、heat shock protein(HSP60)、carboxylesterase(CarE)and(ABC transporter).Two genes was selected from each enzyme group and amount to 14 genes to experiment real time quantitative PCR,Results show:in addition to the CarEgl gene,the results of real-time quantitative PCR of the other 13 down regulated genes were consistent with those of the transcriptome,that is,cotton group as control,AchEgl,AchEg2,NADHgl,NADHg2,HSP60g1,CarEg2 genes expression increased in cucumber group,P450g1,P450g2,GSTg1,GSTg2,HSP60g2,ABCgl,ABCg2 genes expression was down regulated,the results verify the accuracy of the transcript ome conclusion;At the same time,from the common expression,the expression of the two genes of ABC,GST and P450 were significantly down regulated,the gene expression level of cotton aphid living in cotton was significantly higher than that living in cucumber.The two genes selected from AchE and NADH dehydrogenase were significantly up-regulated,the results show that aphid coexistence with the host plant in the long-term lead to the five kinds of enzymes(ABC,GST,P450,AchE and NADH)gene expression level differences.On the one hand,cotton aphid adapt to the needs of host plants,on the other hand,the coevolution of cotton aphid with plants lead to mutual adaptation,that exacerbate the extension of host biotype phenomenon of cotton aphid. |
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