Studies On Interference Lethal Genes In Laodelphax Striatellus (Fallen) And Rice Stripe Virus Base On Rna Interference

The small brown planthopper, Laodelphax striatellus (Fallen), is one of the most important pest on rice production in China. It can suck the sap of crop plants and spread viruses. Rice stripe disease, which caused by rice stripe virus (RSV), is an important rice virus disease and transmitted by small brown planthopper only. Rice stripe disease has turned to be a more and more serious disease since2000following the fast population growth of small brown planthopper.There is not effective method to directly control rice stripe disease at present. Therefore, controling small plant hopper become an important task in rice production. Nowadays, utilising pesticides are still the most widely used strategy in controling small brown planthopper. However, this strategy has been criticized for causing serious pollution problems to food and enviroment.RNA interference (RNAi) is one of the research hotspot in molecular biology at present and can be used in studying gene function. In pest control, it can be used to interfere with important biological process and thereby kill the pest. Therefore, selecting effective RNAi target genes with high specificity is great helpful in developing a new strategy of pest control.The aim of the study is to select effective interference lethal genes in small brown planthopper and RSV genes by RNAi technology. The main results are summarized as follows:1. Three softwares (NormFinder, qBasePlus and BestKeeper) were used to analyze the stability of5internal reference genes (EF, Actin, ARF, GAPDH and β-tubulin). The result by NormFinder was EF=Actin> ARF> GAPDH>β-tubulin, and the result by qBasePlus was EF> Actin> ARF> GAPDH> β-tubulin, while the result of BestKeeper was Actin has the best stability followed by EF. Consistent with the resutls of NormFinder and qBasePlus, β-tubulin was the least stable as evaluated by BestKeeper. Considering the results of three softwares together, genes EF and Actin were treated as the suitable internal reference genes in the quantitative real-time PCR (qRT-PCR) experiments.2. The lethal effects of14genes’dsRNA to the second instar nymphs of small brown planthopper were checked by dsRNA feeding. Six genes (CHIT1, α-tubulin, RL9B, γ-tubulin,UBC, β-tubulin) with the corrected mortality above50%at120h after the dsRNA feeding were selected as effective genes. CHIT gene was the best lethal gene because it had the lowest dsRNA concentration but the best interference lethal effect, the corrected mortality of it reached to62%.3. Three dsRNAs (dsRdRp, dsNSvc4, dsCP) were used to feed2instar L. striatellus (Fallen) with high RSV concentration. At96h after dsRNA feeding, the expression of RSV genes in insects were checked by using qRT-PCR. The results indicated that the expression of NSvc4and CP decreased over95%, while the expression of gene RdRp only decreased by51%-78%. The expression of other genes after feeding specific dsRNAs were also tested. The pilot studies showed that the expression of other genes decreased, which indicated that RSV transcripts might be knocked down with these dsRNAs. This study provides an important basis for controlling RSV through gene sliencing.