Comparative Analysis Of B. Sinensis B And Q Cytochrome P450 CYP6 Subfamily

The Bemisia tabaci(Gennadius)is one of the major invasive pest around the world,which leads to huge economic losses in agriculture production every year.In China,the most serious B.tabaci types are B and Q biotypes.Due to the widespread use of pesticides,whitefly has gained resistance to many insecticides.It has been reported that the resistance of Q biotype to insecticides was significantly stronger than that of B biotype,with the result that Q biotype has become the advantageous biotype in recent years.In this study,the neonicotinoid insecticide thiacloprid,and the analysis of real time quantitative PCR were used to find the candidate gene associated with thiacloprid resistance.In addition,the application of RNA interference technology was used to verify the function of resistance gene provideing an important theoretic foundation for the prevention and controlling of insecticides resistance in whitefly.According to the transcriptome data,we selected two subfamilies of cytochrome P450 CYP6 CX and DW as the target genes,and screened out 12 pairs of RT-qPCR primers for genes in CX and DW subfamilies.The new insecticide thiacloprid of high efficiency was chosen to determine the toxicity of B and Q biotype of Bemisia tabaci.The mortality rate of B and Q biotype showed that the resistance of Q biotype was significantly higher than that of B biotype Bemisia tabaci,and the experimental results were consistent with the results of previous studies.Using real-time quantitative PCR,the differences of gene expression between pesticide-untreated B and Q biotype Bemisia tabaci were analyzed.It was found that the expression of most genes in the Q biotype was higher than that in the B biotype.Then,the expression of the target genes were analyzed after pesticide thiacloprid treatment.The results showed that the expression levels of CX5,CX6,CX7,and DW2 genes were up-regulated.The expression levels of CX5 and CX7 showed positive correlation with the drug concentration in some degree,which showed that these genes played important roles in the insecticide resistance of Bemisia tabaci.According to the results of previous experiments,the CX5 gene that significantlyup regulated was selected as the target gene of RNAi interference,and the CX5 gene was successfully silenced with feeding method.B and Q biotype Bemisia tabaci in which the target gene was silenced by RNAi were treated with pesticide thiacloprid,and the mortality rates were caclucated invidually.The results showed that the mortality rate of Bemisia tabaci in which the target gene was interfered was higher than that of the control group,indicated that the CX5 gene played an important role in the pesticide resistance.