| Bombyx mori is not only an important economic insect,but also an important model insect widely used in biological research.However,the developmental process of the silkworm is extremely sensitive to virus infection,especially the Bombyx mori nucleopolyhedrovirus(BmNPV)infection.Therefore,studying the BmNPV resistance mechanism of the silkworm is of great significance to the development of the silkworm industry.In this study,the BmNPV-resistant silkworm strain(NB),BmNPV-sensitive silkworm strain(306),trait segregated populations BC1 and BmNPV were used as the main experimental materials to explore the BmNPV resistance mechanism of NB through genomics and transcriptomics analysis methods.The main results obtained were as follows:1.Localization of the BmNPV resistance geneBy performing 2b-RAD simplified genome resequencing of NB,306 and 152BC1 trait segregated populations,SNP/In Del genetic markers in the genome were developed and a genetic map was constructed.Finally,a genetic map with a total map distance of 3,771.53 c M was constructed,which contained 3,131 molecular markers.Quantitative trait locus(QTL)localization analysis finally obtained two BmNPV resistance trait-associated regions at 8,278,320 bp to 18,044,074 bp on chromosome 3and 7,770,111 bp to 14,463,318 bp on chromosome 27,respectively.There were4,611 SNPs and 242 In Del mutation sites in the QTL regions,as well as 234 genes with mutation sites,of which 132 genes had functional mutation sites.2.Transcriptomics analysis of the response of different strains and genders of silkworms to BmNPV inoculationDifferent genders of NB and 306 were respectively inoculated with BmNPV,and control groups were set up as well.Transcriptome sequencing technology was used to identify the different responses of different genders and different strains of silkworm to BmNPV inoculation.And 18 BmNPV resistance candidate genes were finally obtained through the transcriptomics analysis,including a gene located in the QTL region: Fungal Protease Inhibitor F-like,which might play a role in the process of BmNPV resistance.Nine resistance candidate genes were differentially expressed in different genders of NB inoculated with BmNPV,suggesting that NB of different genders had certain differences in the process of BmNPV resistance.3.Genome sequencing of NB and comparative genomics analysisDe novo genome sequencing of NB was performed using the third-generation,second-generation,and Hi-C sequencing technology.Finally,a high-quality chromosome-level genome assembly with a total length of 455.46 Mbp was obtained.The annotation results showed that the NB genome contained 13,103 genes,with repetitive sequence accounting for 56.54%,and nc RNA sequence accounting for0.31%.Through comparative genomics analysis of 18 species including NB,it was found that some gene families related to membrane component,transmembrane transport activity,and catalytic activity had been expanded during the evolution of NB.Two genes related to the immune response: Pal1 and Cdc7 had positive selected non-synonymous mutations.It was speculated that the BmNPV resistance traits of NB might be due to changes in some membrane components including transmembrane proteins during its evolution process,leading to the ability of NB to recognize BmNPV and activate the innate immune response.At the same time,some biological enzymes including PAL1 and CDC7 related protein kinase might play important roles in the process of BmNPV resistance. |
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