Effects Of Prey Variation On The Development And Fecundity Of Propylaea Japonica And Fuction Analysis Of Genes Insulin Signaling

Propylea japonica is an important predatory natural enemy insect widely distributed in farmland.It has great potential for biological control and is one of the important means to achieve the goal of pest control.In this experiment,the reproductive effects of several prey species were determined by feeding different prey to P.japonica Expression profiles of 8important genes in the insulin signaling pathway（IRS1,E（sev）2B,TOR,PDK1,PI3K,AKT,MAPK and RPS6KB）in different developmental stages（1,3,5,7 days after eclosion）and tissues（head,chest,abdomen,intestine）of P.japonica were identified with the method of real-time quantitative PCR,and the expression changes of genes after feeding on Megoura crassicauda and Mythimna separata were also investigated.The effects of IRS1 gene interference on ovary and ovarian follicular epithelial cells of P.japonica were analyzed by using RNAi technology.The purpose of this study was to explore the possibilities of feeding P.japonica via inexpensive preys,clarify the role of insulin signaling pathway in the reproductive development of P.japonica,and provide a theoretical basis for large-scale propagation of P.japonica.The main results are as follows:（1）By feeding P.japonica with different preys,it was found that the P.japonica larvae fed on M.crassicauda could grow and develop normally,but all the P.japonica larvae fed on M.separata,Drosophila melanogaster and Helicoverpa armigera all died.Adults of P.japonica could lay eggs normally when feeding on M.crassicauda,few eggs when feeding on M.separata and D.melanogaster,but no eggs when feeding on H.armigera.（2）After feeding on the M.crassicauda and M.separata,the adults of P.japonica were dissected.It found that the ovaries of P.japonica female feeding on M.crassicauda can develop normally,while the ovaries of P.japonica adults that feed on M.separata showed no significantly changes from 1 d to 7 d post emergence.（3）The results of q RT-PCR analysis showed that the expression levels of eight important genes in the insulin signaling pathway（IRS1,E（sev）2B,TOR,PDK1,PI3K,AKT,MAPK and RPS6KB）were significantly up-regulated at the 7^th day of adult emergence.Expression patterns of 8 genes were divergent in different developmental stages（1,3,5,7 days after eclosion）and tissues（head,chest,abdomen,intestine）of P.japonica.The expression levels of8 genes were different between the P.japonica female feeding on M.crassicauda and M.Separata.Generally,t it showed that the gene expression levels of these genes in the female feeding on M.crassicauda were significantly higher than those feeding on M.separata.（4）The ds RNA was introduced into P.japonica by microinjection to silence the IRS1gene,and the silencing efficiency was detected at 24 h,72 h and 120 h by q PCR.The results showed that the IRS1 gene expression level was significantly down-regulated at 24 h and 72 h after interference,while no difference was observed at 120 h after interference.In addition,when the expression of IRS1 was inhibited,P.japonica could not lay eggs normally.The ovary was dissected and stained for cytoskeleton and nucleus.It was found that after IRS1gene silencing,ovarian development was slow,and primary oocytes hardly grew,follicular epithelial cells were tightly packed,and the gap for vitellogenin could not be formed.