| Insectcides play a main role in control of major vectors of diseases. However, development of resistance in many insect species represents a significant and increasing thread to their continued effective use. It is important and urgent to elucidate the resistance mechanism in order to slow down the spread and development of resistance of vector populations. Most studies on the resistance-related mechanism of Aedes albopictus were mainly focused on the occurrence, development and biochemistry of the resistance, there are very few of research based on molecular biology, although Ae. albopictus is very important vector species. In this research, a resistance strain which has been selected in lab (R-lab) for many years was used as a study model, a biochemistry and molecular method have been adopted to find out the resistance-related mechanism in R-lab, and some resistance-related genes had also been identified by SSH, in order to obtain further understanding of pyrethroid resistance of Ae. albopictus based on the molecular genetics.1. Bioassay and biochemical analyses of R-lab.Metabolism detoxification mechanisms are one of the major resistance mechanisms in R-lab by the analyses of synergistic action and effect of detoxifying enzyme. The increased activity of Cytochrome P450 monooxygenases(P450s) was a main factor in metabolism detoxification mechanisms, GSTs have a role and EST probably have a minor role in pyrethroid resistance of R-lab.2. The action of knockdown resistance (kdr) in R-lab2.1 Sequence analysis of the voltage-dependent sodium channel in Ae. albopictusA total 6304bp of sodium channel gene had been amplified and sequenced by RT-PCR and RACE from S-lab. It has been demonstrated that 2058 aminoacid are encoded including four homologous domains and the hydrophilic linking peptides of varying length without 3 UTR. Although it is incomplete in this para-like cDNA sequence in Ae. albopictus, but it is long enough to find out the kdr mutation in Ae. albopictus because it contains all of the mutations that have been reported to be related with kdr. It was found that the closest sequence homology to the Drosophila para sodium channel with 83. 1% sequence identity, and with 46. 2% sequence identity with RatI which is rat brain I sodium channel by comparison of the sodium channel gene sequence with other cloned sodium channel. It means Ae. albopictus para homologous have been cloned.2.2 cDNA sequence analysis of the sodium channel of the pyrethroid-resistance of Ae. alboptictus.The cDNA sequence of IIS4-IIS6 in which Mr mutation located and the whole cDNA sequence have been analyzed from the resistance individuals. Resistance-related mutation has not been found. These results indicates that kdr perhaps has a minor role in pyrethroid resistance of R-lab.2. 3 Alternative splicing of sodium channel gene in Ae. albopictusEight alternative exons have been found in sodium channel gene from a high resistant individual and the exon m and exon n are found firstly in insect sodium channel. It is indicated that alternative splicing widely exists in sodium channel gene of mosquitoes. A further study is needed to be done on the action of the alternative splicing.3. Study on the resistance-related gene of R-labSuppression subtractive hybridization (SSH) technique is employed to construct both of the differentially expressed gene segments libraries between the R-lab and S-lab. One is the forward libraries which R-lab is tester, S-lab is driver; the other is reverse libraries which S-lab is tester and R-lab is driver. 160 clones are arbitrarily selected to sequenced from the forward libraries and 134 clones were obtained with the sequence length(177-600bp). By analysis with bioinformatics methods, these 134 clones include 8 known Ae. albopictus sequences, 21 homologoussequences of known mosquitoes genes such as Aedes. aegypti and Anopheles, gambiae, 2 homologous sequences of other known organism gene, 16 homologous sequences of known sequence but no function clues and 89 unknown gene segments. Two...
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