The Mechanism Whereby Jinggangmycin Induced ILP2 Modulates The Reproduction And Population Of Brown Planthopper,Nilaparvata Lugens(St(?)l)

The brown planthopper(BPH),Nilaparvata lugens(Stal)(Hemiptera:Delphacidae),is a classic insecticide-induced resurgence insect pest of rice cropping system.The antibiotic fungicide jinggangmycin(JGM)enhanced fecundity of BPH is closely intertwined with fatty acid metabolism as revealed by our previous work(Zhang et al.,2015;Li et al.,2016;Jiang et al.,2016;You et al.,2016).However,other modulatory networks involving in the JGM-induced fecundity increase of BPH are uncharted.We analyzed the gene expression profile of the BPH(2 days postemergence,2d PE)treated with JGM and found insulin-like peptides(ILP2),based in the insecticide-induced insulin signaling pathway,was significantly up-regulated.Whereas whether the up-regulation of NlILP2 underlies the mechanisms of JGM-enhanced fecundity remains elusive.In this paper,the RNA interference technique,bioassays,qRT-RCR,western blot and immunofluorescence were performed to elucidate the mechanism whereby NlILP2 modulates fecundity of BPH and its population growth.The results are detailed as follows:1.Transcriptomic analysis of female adults post JGM treatment at 2d PETranscriptomic analysis against female BPHs treated with JGM at 2d PE was performed via RNA-seq technique.A total of 1165 differentially expressed genes were identified,with 557 genes up-regulated and 608 down-regulated.Additionally,this analysis yielded 317 pathways among which 16 pathways correlate with hormonal and reproductive regulation.Pathway annotation and enrichment analysis were conducted to screen the up-regulated NlILP2.To highlight the role of NlILP2 in JGM-stimulated fecundity mechanisms,qRT-PCR was employed to investigate the expression profile of NlILPs gene family(NIILP1-NlILP4)and RNA interference was used for NIILP2 silencing to provide cues for its gene function study.2.Silencing NlILP2 influences fecundity of BPH and its offspring populationDietary dsNIILP2 treatments led to reduced transcript level of NlILP2,by circa 36.4%?74.6%at 1,3,5,and 7d PE.Post JGM+dsNlILP2 treatment,the fecundity of the brown planthopper significantly diminished relative to the JGM-treated group,as registered by 63%decreased egg-laying,57.4%reduced for offspring population and 17.7%for egg hatching rate,and preoviposition period was prolonged up to 36%,oviposition period shortened by 28%,whereas no significant difference for the sex ratio of progeny.Silencing NlILP2 resulted in retarded ovary development in females after 2d,4d,and 6d post emergence.Upon NIILP2 knockdown,fat and ovary protein content decreased by 66%and 59%,respectively,and Nlvg transcript levels at 2d PE and 3d PE dropped by 45%and 37%respectively.Besides,the signal of vitellogenin detected by immunofluorescence(IF)also weakened dramatically at 2d PE post silencing.The amount of yeast-like symbiotes in female fat bodies of JGM+dsNlILP2 treatment was significantly lower than that of the JGM-treated insects,down by 48%,also reduced were insulin content(by 34%)and juvenile titer(by 19%),while 20E titer rose by 30%,meanwhile JGM+dsNlILP2-treated females at 2d PE tend to possess decreased body weight and dwarf body size.