Abstract
BackgroundBombyx mori was domesticated from the Chinese wild silkworm, Bombyx mandarina. Wild and domestic silkworms are good models in which to investigate genes related to silk protein synthesis that may be differentially expressed in silk glands, because their silk productions are very different. Here we used the mRNA deep sequencing (RNA-seq) approach to identify the differentially expressed genes (DEGs) in the transcriptomes of the median/posterior silk glands of two domestic and two wild silkworms.ResultsThe results indicated that about 58% of the total genes were expressed (reads per kilo bases per million reads (RPKM) ≥ 1) in each silkworm. Comparisons of the domestic and wild silkworm transcriptomes revealed 32 DEGs, of which 16 were up-regulated in the domestic silkworms compared with in the wild silkworms, and the other 16 were up-regulated in the wild silkworms compared with in the domestic silkworms. Quantitative real-time polymerase chain reaction (qPCR) was performed for 15 randomly selected DEGs in domestic versus wild silkworms. The qPCR results were mostly consistent with the expression levels determined from the RNA-seq data. Based on a Gene Ontology (GO) enrichment analysis and manual annotation, five of the up-regulated DEGs in the wild silkworms were predicted to be involved in immune response, and seven of the up-regulated DEGs were related to the GO term “oxidoreductase activity”, which is associated with antioxidant systems. In the domestic silkworms, the up-regulated DEGs were related mainly to tissue development, secretion of proteins and metabolism.ConclusionsThe up-regulated DEGs in the two domestic silkworms may be involved mainly in the highly efficient biosynthesis and secretion of silk proteins, while the up-regulated DEGs in the two wild silkworms may play more important roles in tolerance to pathogens and environment adaptation. Our results provide a foundation for understanding the molecular mechanisms of the silk production difference between domestic and wild silkworms.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1287-9) contains supplementary material, which is available to authorized users.
Highlights
Bombyx mori was domesticated from the Chinese wild silkworm, Bombyx mandarina
RNA-sequencing and identification of novel transcripts To explore differences in the silk gland transcriptomes between domestic and wild silkworms, two domestic strains, Chunhua (D_CH) and Chunyu (D_CY), and two wild silkworms were selected for analysis
In summary, this study represents a significant step in the characterization of silk gland transcriptomes and provides insights into the molecular mechanisms of silk production
Summary
Bombyx mori was domesticated from the Chinese wild silkworm, Bombyx mandarina. Wild and domestic silkworms are good models in which to investigate genes related to silk protein synthesis that may be differentially expressed in silk glands, because their silk productions are very different. We used the mRNA deep sequencing (RNA-seq) approach to identify the differentially expressed genes (DEGs) in the transcriptomes of the median/posterior silk glands of two domestic and two wild silkworms. Silk produced by domestic silkworms has been a widely sought fair textile material. B. mori was domesticated from the Chinese wild silkworm, Bombyx mandarina, approximately 5000 years ago [1,2,3]. The silk proteins (fibroins and sericins) are produced by silk glands. MSGs synthesize the glue proteins (sericins), which are composed of seven major sericins that
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