Molecular Dynamics Of Plutella Xylostella Immune Response Against The Infection Of Isaria Fumosorosea

The entomopathogenic fungi Isaria fumosorosea has the potential to control Plutella xylostella as the invasive activity of I.fumosorosea inhibits the immune system of P.xylostella.To better understand the interaction mechanism of P.xylostella and I.fumosorosea,in the present study,P.xylostella was challenged with I.fumosorosea at four different time points(12 h,18 h,24 h,and 36 h).The transcriptome and small RNA libraries of P.xylostella were used to screen out immune genes and miRNAs following I.fumosorosea infection.Furthermore,RT-qPCR was used to verify the expression profile of Plutella xylostella.The dynamics of immune-related mRNA-miRNAs molecular network was constructed and the critical time point of Plutella xylostella immune defense mechanism against I.fumosorosea was selected for further experiments.To further deepen our study,iTRAQ was used to determine and screen the critical proteins of Plutella xylostella immune defense in response to I.fumosorosea infection.,The dynamics of molecular regulation network of P.xylostella immune defense against I.fumosorosea was clarified.The main results are summarized as follows: 1.The symptoms and histopathologic changes of P.xylostella after infected with I.fumosoroseaIn 12 h,18h,24 h and 36 h,the results showed that disease and pathological changes of diamondback moth at different time,and the results provide detailed biological data for the study on the immunity of P.xylostella against the infection of I.fumosorosea.It provides an important basis for the selection of sequencing time points in the next step of the study.2.The transcriptome data analysis of the immune responses of P.xylostella against I.fumosoroseaThere are 161 immune related genes expressed in significant differences after I.fumosorosea infection.There were 15,13,53,14 immune related genes up – regulated,and 38,51,56,49 down – regulated at 18 h,12 h,24 h and 36 h,respectively.The number of genes related with antimicrobial peptides were significantly decreased.Above results indicate that I.fumosorosea can restrain the immune response of the diamondback moth,and has the ability to become a potential biological pesticide for controlling P.xylostella.3.The identification and analysis of miRNAs of P.xylostella after infected with I.fumosoroseaWe identified 116 known miRNAs with precursor sequences and predicted 42 novel miRNAs.There were 23 known miRNAs which were significantly differentially expressed.The miRNAs,which were abundantly expressed are;pxy-mir-7b-5p,pxy-mir-2768-3p,pxy-mir-79-3p,pxy-mir-8507-3p,and pxy-mir – 2a-3.In addition,we predicted 30699 target genes of miRNAs by RNAhybrid,miRanda,and Target Scan.4.The joint analysis of mRNA and miRNAwe finally screened 7 pairs of miRNA-target genes.Through KEGG database screening,we found that five of the target genes were involved in the signaling pathway related to immunity,among which the target genes scavenger receptor regulated by pxy-mir-2796-3p(gene ID: 105394486)was involved in the lysosome pathway KO04142 and phagosome(KO 04145).It plays an important role in the infection of insect immune fungi.5.The immune responses of P.xylostella analyzed by ITRAQ quantitative proteomicsThe iTRAQ of P.xylostella was determined 24 hours after infection.we identified 20708 peptides,and 3861 proteins.There were 202 proteins significantly differentially expressed,94 proteins were up-regulated,108 were down-regulated.The results showed that differentially expressed protein molecules might affect the immune defense of P.xylostella.This provides useful information for understanding the interaction between I.fumosorosea and P.xylostella.6.The correlation analysis of proteomics and transcriptomeThrough the combined analysis of transcriptome and proteomics,3861 proteins and 17057 genes were identified,among which the associated number was 3811.After obtaining the information of gene structure and sequence,in order to obtain further functional information of the genes,35 pairs of differentially expressed proteins-significantly differentially expressed genes were screened.The strong association between proteomic and transcriptional groups is helpful to find out the regulation of gene expression.Target genes were involved in immune-related signaling pathways,such as melanogenesis biosynthesis signal pathway(KO04916),lysosome signal pathway(KO04142),phagosome signal pathway(KO04145),peroxisome signal pathway(KO04146),fatty acid degradation metabolism signal pathway(KO00071),and pancreatic secretion signal pathway(KO04972).In conclusion,transcriptional data combined with proteomics data showed that,I.fumosorosea infects P.xylostella by inhibiting host immune response and regulating metabolism.Therefore,this study provides an important insight into immune response and regulating metabolism of P.xylostella.