Functional Analysis Of Doublesex Gene In Sogatella Furcifera And Laodelphax Striatellus

The white-backed planthopper（WBPH）,Sogatella furcifera and the small brown planthopper（SBPH）,Laodelphax striatellus,（Delphacidae,Hemiptera）,have gradually become important pests that threaten rice production in China in recent decades.Doublesex gene,as a nexus of insect sex determination and sex differentiation,is a key gene in insect sex determination,and plays an important role in the reproduction for insect population.Hence,functional analysis of dsx homologs in WBPH and SBPH will help us better understand sex determination mechanism in planthoppers,and will provide a theoretical basis for the pest control.In this study,four splicing patterns of dsx were found in WBPH by sequence analysis.Domain analysis revealed that all four transcripts contain a typical conserved domain of DM/OD1,which are conserved among all insects dsx amino acid sequences,but there is no OD2 domain in Sfdsx,which indicates the sex determination mechanism of WBPH may be different from other studied insects.The comparison showed that the OD1 domain of the male and female common area is relatively conservative,and the key amino acid residues are highly conserved.The female specific region of Sfdsx are distinctly different from those of other insects,and the male specific region are various among insects.Using the semi quantitative PCR technique,Sfdsx^F1 and Sfdsx^F2 were identified as the female-specific splice forms,while Sfdsx^M1 and Sfdsx^M2 were the male-specific splice forms.RNA inference（RNAi）using the double strand RNA targeting the common region and male specific region of Sfdsx showed that male copulatory apparatus and inner reproductive system are abnormal,but no obvious changes on the female ovipositor and inner reproductive system were observed.In addition,knockdown of Sfdsx M lead to a remarkable increase in the body sizes of the males.These results implied that Sfdsx may play a crucial role in the regulation of male somatic and sexual development.Furthermore,we have also achieved a gene Ls3901 in SBPH by searching against the local transcriptomic databases,which was the most homologous to Sfdsx.Using RNA interference,the result showed Ls3901 had the same function as Sfdsx.Our results provided a basis for the further study on the mechanism of sex determination of two rice planthoppers,and provided a potential targets for the RNAi-based or genesis-based planthopper control.