The Effects Of Bcutra On Sex Determination In Bactrocera Cucurbitae

Bactrocera cucurbitae(Copuillett)is classified into Bactrocera Macquar,family Tephritidae,order Diptera.It is a worldwide quarantine pest and one of the important quarantine pests in China,which can do harm to 125 host plants.Chemical control,which badly effects on environment and human health,is the most common method to control B.eucurbitae.Therefore,new control method should be developed.The genetic engineering technology,which is used to induce sex imbalance in insects in order to achieve the goal of population control,is a new way to control B.cucurbitae.Transformer(tra)is a key gene in sex determination of many sexually dimorphic insects,especially in Diptera insects.The protein produced by tra with the protein of transformer 2(tra 2)activates specific splicing in the terminal genes of cascade reaction and produces Dsx protein,which promotes the development of female individuals.Sex-determining gene tra(Bcutra)has been isolated and identified in B.cucurbitae,but its sex-determining mechanism has not been clearly understood until now.In this study,B.cucurbitae is the research object.R.NAi technology was used to microinject Bcutra double-stranded RNA(dsRNA)into embryos,and then the effects of Bcutra on sex determination were studied.The experimental results are as follows:1.The study suggested that the ratio of female and male was nearly 1:1 in two control groups whether Venus dsRNA was injected or not.2.More than 90%of male adults could be obtained by RNAi embryonic micro-injection of two different fragments of Bcutra dsRNA in Bcutra gene.It is concluded that Bcutra gene has effects on sex development.3.Through the test of RNAi male fecundity,it was found that only 45.0%and 37.5%of males respectively injected Bcuira-384 dsRNA and Bcutra-738 dsRNA could mate with wild-type females.And the males with fertile offspring they produced accordingly accounted for 37.5%and 30%.4.Subsequently,all the males tested for fertility were dissected.An abnormal internal genital containing testis and ovaries was found in some intersex individuals microinjected with Bcutra dsRNA embryos.At the same time,a large and a small abnormal testis or two small ones were found in some of the RNAi males.5.By analyzing the expression of Bcudsx genes in RNAi unmated males,it was discovered that RNAi unmated males contained a 1107bp-sized female-specific transcript of Bcudsx and a 484bp-sized male-specific transcript of Bcudsx.Therefore,the study showed that Bcutra gene could induce the XX females to develop into males,and the unmated RNAi males were unfertile pseudo-males.In this study,it successfully studied the effect of Bcutra,a sex-determining gene on the sex determination of B.cucurbitae by RNAi technique.The sex-determining gene Bcutra was silenced by embryo microinjection,and the transformation of XX females into males was successfully induced.The results of this study not only made a big breakthrough in the field of sex determination mechanism,but also provided theoretical support and technical guidance for controlling B.cucurbitea by new control methods of genetic engineering.