Effect Of Four Chitinase Genes On The Female Fecundity In Sogatella Furcifera (Horváth)

Sogatella furcifera(Horváth)is a long-distance migratory rice pest with strong female reproductive capacity,particularly in terms of prolonged oviposition periodsand high egglaying rates,which makes it susceptible to outbreaks.Reproduction is an important factor for the maintenance and continuation of insect populations,as well as a crucial topic in pest control research.Currently,the research has identified 12 chitinase genes,of which four genes(SfCht2,SfCht6-2,SfIDGF1,and SfENGase)showed high expression levels in the ovary and fat body of S.furcifera,suggesting their potential involvement in regulating the reproductive system of this pest.Therefore,in this study,we focused on S.furcifera and used real-time quantitative polymerase chain reaction(RT-q PCR)technology to analyze the spatial and temporal expression patterns of the four chitinase genes in female insects.Using RNA interference(RNAi)methods,we investigated their effects on the fecundity of S.furcifera.After silencing the four chitinase genes,we measured the transcription levels of genes related to reproduction of S.furcifera and combined transcriptome sequencing technology to preliminarily analyze the potential molecular mechanisms by which SfENGase gene effects reproductive development.The principal research findings are summarized as follows:1.Analyzing the spatial and temporal expression patterns of the four chitinase genes in female S.furcifera(1)The m RNA levels of SfCht2 and SfIDGF1 in females showed an increasing trend followed by a decrease after eclosion,while SfCht6-2 exhibited significant fluctuations during growth process.Additionally,the transcriptional level of SfENGase was highest on the first day females.(2)Chitinase genes SfCht2,SfCht6-2,and SfENGase were relatively highly expressed in the ovaries of S.furcifera,whereas the expression level of SfIDGF1 in the ovaries was only second to that in the legs.(3)SfCht2 and SfIDGF1 were mainly highly expressed in the late stage of ovarian development,while SfCht6-2 exhibited large fluctuations during ovarian development.In addition,during the progression of ovarian development,the transcriptional level of SfENGase showed an increasing-decreasing pattern.(4)SfCht2,SfCht6-2,and SfENGase were all highly expressed in the fat body of females on the first and second days after eclosion,while SfIDGF1 showed the highest expression level on the seventh day after eclosion.2.Clarifying four chitinase genes participated in reproductive process of S.furcifera(1)dsSfCht2,dsSfCht6-2,dsSfIDGF1 and dsSfENGase were successfully silenced in newly emerged females when compared to the control group(dsGFP),and the average lifespan of the insects was significantly reduced.(2)In the group treated with dsSfCht2,dsSfCht6-2,dsSfIDGF1 and dsSfENGase,their ovaries were inhibited by 25%,35%,30%,and 45%,respectively,and the egg-laying period of the whiteflies was significantly shortened.However,only the egg-laying pre-stage of the SfENGase silenced group was significantly delayed.(3)Following the injection of dsSfCht2,dsSfCht6-2,dsSfIDGF1 and dsSfENGase,the egg-laying capacity of female of S.furcifera showed a significant reduction compared to the control group(179.54),which resulting in a decrease of 45.90%,48.36%,53.83% and58.62% respectively,but did not affect the hatching of eggs.3.Preliminary study of the molecular pathways on reproductive regulation of four chitinase genes(1)Silencing of SfCht2,SfIDGF1,SfCht6-2 and SfENGase resulted in a significant decrease in the expressions and contents of the SfVg and SfVg R genes in S.furcifera.(2)Silencing of the four chitinase genes caused a significant decrease in the expression levels of 70%～90% of genes in the JH signaling pathway.Silencing of SfCht6-2 and SfENGase restrained on the expression levels of reproductive genes in the TOR signaling pathway.(3)Silencing of the SfENGase gene resulted in changes in key genes of vitellogenin production,TOR signaling pathway and fatty acid synthesis and metabolism.These results indicated that four chitinase genes(SfCht2,SfCht6-2,SfIDGF1 and SfENGase)are involved in the regulation of reproduction in female S.furcifera.Interfering with these four chitinase genes led to a decrease in the expression levels of reproductionrelated genes in the vitellogenin/vitellogenin receptor,juvenile hormone,and TOR signaling pathways.Additionally,the SfENGase gene can inhibit vitellogenin synthesis by affecting the TOR signaling pathway and the fatty acid pathway,thus affecting the ovarian development of S.furcifera.The results of this study have enriched our understanding of the biological functions of insect chitinases,and provided a new target for the development of control technologies against the S.furcifera.