| The organisms rapidly evolved to cope with the climate changes and humans activity including the enhanced Ultraviolet (UV), the increase of CO2 concentration, the application of insecticides and Bt-transgenic crops extension.Silent transposable elements (TEs) can be activated by environmental stress. How to speed up the pest evolution for transposon? Is genomic DNA mutation of its host related with the activity, dynamics of transposon? Whether can the transposon be employed as marker to identify the mutation of host pests?The cotton bollworm (Helicoverpa zea), sweetpotato whitefly (Bemisia tabaci), green peach aphids (Myzus persicae), as three world-wide destructive pests, their genetic evolutions were affected by the human intervention and climate changes. Rapid acquiring of insecticide resistance of H. zea to Bt-transgene crops in H. zea, biotype differentiation in B. tabaci and subspecies differentiation in M. persicae. TEs not only constitute a large fraction of some genomes, but involve in the regulation of host defense against environment. Therefore, based on the relations of environment, pest and transposon, genetic structures of eight populations were assessed using transposon display technique with pest-transposon as subjects. Also, according to the transposon dynamics and PCR results, this study tested the characteristics of transposon including the activity, function, natural history and potential application.Transposon display could be conducted to elucidate the population genetic structure. Hztransib from H. zea has the potential to be used as gene drive agent for controlling mosquito-borne disease. MITE from B. tabaci may be exploited to identify biotypes as molecular marker. In addition, Suppression Subtractive Hybridization (SSH) was employed to identify differentially expressed genes between the control and UV-induced aphids.Therefore, the results showed the following aspects:(1) Intragenomic dynamics of Hztransib in H zea with transposon display Transposon Display found a total of 39 Hztransib insertion sites from 4 laboratory and 4 field populations of H. zea (16 individuals per population) and revealed the presence of at least 1 intact Hztransib copy in all the 128 individuals tested. All the 39 genomic sites were polymorphic. The equilibrium copy number of Hztransib per individual ranged from 5.83 copies in the Benson strain to 14.21 copies in the Pop 2 strain. Multiple comparisons indicated that the average insertion sites per individual were significantly higher in the DK6971 and Benzon strains than in the other six strains (Turkey's HSD test, p < 0.05). These data suggest that Hztransib is currently capable of increasing its copy number in its host genome.(2) Natural history and current richness of Hztransib Genomic PCR were conducted to elucidate natural history and current richness of Hztransib. The intact ORF (open reading frame) of Hztransib was present in H. armigera from which H. zea was established via a founder event at around 1.5 million years ago and H. assulta, the common ancestor of H. zea and H. armigra. And the intact copies were always more abundant than the internally-deleted ones. Taken together, while Hztransib has persisted for at least 1.5 million years in H. zea and H. armigera, it still possesses the capacity to maintain its structural integrity.(3) Transpositional activity of intact Hztransib and its mutation in insect cell lines To break the host silent mechanism, the silent mutations were introduced to the Hztransib including point mutation, multiple points mutation and area mutation. The mutant vector will try to destroy the alternative polyA position and the controlling polyA position was located downstream 28 bp of stop codon at 3'end of Hztransib.(4) Obtain of the MITEs in B. tabaci According to the insertion polymorphism and current technical limitation, MITEs were subsequently exploited in the development of a powerful molecular marker with transposon display. Here, five MITE genes were discovered in the whitefly by designing the degenerate primer. They are highly repetitive with characteristics including lacking coding capacity, high copy number (polymorphism sites), high AT content and the potential to form strong secondary structures.(5) Construction of MITEs-based genetic marker New molecular marker takes advantage of transposons-MITEs. The suitable MITE was selected and the system was optimized. The technique of MITE-based molecular marker was finally constructed. Based on its insertion polymorphism, we thereby assess the potential of MITEs for identifying genetic variation between and within biotypes by segregation study, reproductive test. The results suggested that the MITE-based marker may provide a reliable diagnostic tool for identifying the biotypes and the genetic variation within biotypes.(6) SSH library identified a collection of predicted UV-B induced genes which encode proteins associated with stress, nuclear acid and fatty-acid metabolism, transcription, protein synthesis. The data revealed that the growth of aphid population depended on the dose of UV-B radiation and aphids might regulate gene expression for protection against UV-B damage.
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