| Plutella xylostella is one of the major pests in many crucifers and causing severe damages.The continuous application of chemical pesticides has made this pest resistant to many chemicals.Therefore,novel methods are needed to control the pest,and biocontrol agents have shown great potential.Beauveria bassiana is one of the most widely studied and used biological pesticides,Analysisof host-pathogen interaction related genes is the basis for efficiency improvement for B.bassiana against P.xylostella.In this study,Firstly,we obtained the most virulent B.bassiana strainagainst Plutella xylostella from 20 B.bassiana strains isolated from different agroclimatic regions.Secondly,The transcriptome of P.xylostella larvae at 48 hours post treatment of infection were analyzed for getting insight into the host-pathogen interaction related genes by high-throughput sequencing.Meanwhile,the genes differentially expressed in fungi and insects during infection process and pathogenesis were screened and the function of these genes were analyzed.This study provides new insight into geneinteraction between B.bassiana and Plutella xylostellaas as well as the genetic basis for eontol efficiency improvement of B.bassiana against Plutella xylostellaas.The main results are as follows:1.Screening of high virulent strains of B.bassiana against Plutella xylostellaWe tested 20 strains of B.bassiana against 2nd instar of Plutella xylostella.Finally,5 strains?Bb2393,Bb 2391,Bb2361,Bb2356 and Bb2345?showed higher virulence with median lethal time ranged from 4.59d,5.17d,5.38d,5.3d,5.5d,respectively.Similarly,half lethal concentrations were recorded as 1.48×105,3.10×105,6.18×105,6.95×105,1.27×106 spores ml-1,respectively.The bioassay results showed that Bb2393 had the strongest adaptive capacity under different temperature conditions.And 88.69%corrected mortality of 25°C with the least time mortality 4.32days was recorded.It suggested that Bb2393 are the most suitable strain in biocontrol of Plutella xylostella.2.Analysis of infection and pathogenicity related genes in B.bassianaPaired analysis of DGE libraries derived from B.bassiana infecting larvae for 48h and pure-cultivating B.bassiana was conducted.8383DGEs were obtained,which included 716 significantly differentially expressed genes?FDR?0.001 and log2Ratio?1?.There were 350 up-regulated genes and 366 down-regulated genes.GO annotation was used to analyze the DEGs and found 26 terms,which included Biological processes?11?,Cellular component?8?and Molecular function?7?.93 up-regulated genes and 61down-regulated genes in Bb2393 were enriched in 12 KEGG pathways?Pvalue?0.05?.Further analysis showed that many DEGs were enriched in infection and virulence processes,includingchitinase1,acidic chitinase,antigenic cell wall galactomannoprotein and extracellular serine-rich protein.In addition,we obtained some genes which may not be reported in the early stage.And the role of these genes in the infection process needs to be further verified.3.Analysis of immune related genes of Plutella xylostella against B.bassianaPaired analysis of DGE libraries derived from the infected?48h?and uninfected?control?larvae,which revealed 15542 differentially expressed genes.These genes including 2434 significantly differentially expressed genes?FDR?0.001 and log2Ratio?1?.Besides,1080 genes were up-regulated and 1354 genes were down-regulated in these DEGs.GO annotation was used to analyzed the DEGs and found 45GO terms,which included Biological processes,Cellular component and Molecular function.The DEGs were enriched in 298 KEGG pathways like Ribosome,Endoplasmic reticulum protein processing and pancreatic secretion.Further analysis showed that 25 KEGG pathways?Pvalue?0.05?contained peptidoglycan recognition protein,phenol oxidase and serine protease,which were closely related to host immunity.These findings of genes related to immunity of diamond back moth provided genetargets for promoting pathogenicity of Beauveria bassiana against Plutella xylostella. |
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