Differentially expressed genes in the head of the 2nd instar pre-molting larvae of the nm2 mutant of the silkworm, Bombyx mori

Abstract

Molting is an important physiological process in the larval stage of Bombyx mori and is controlled by various hormones and peptides. The silkworm mutant that exhibits the phenotype of non-molting in the 2nd instar (nm2) is incapable of molting in the 2nd instar and dies after seven or more days. The ecdysone titer in the nm2 mutant is lower than that in the wildtype, and the mutant can be rescued by feeding with 20E and cholesterol. The results of positional cloning indicated that structural alteration of BmCPG10 is responsible for the phenotype of the nm2 mutant. To explore the possible relationship between BmCPG10 and the ecdysone titer as well as the genes affected by BmCPG10, digital gene expression (DGE) profile analysis was conducted in the nm2 mutant, with the wildtype strain C603 serving as the control. The results revealed 1727 differentially expressed genes, among which 651 genes were upregulated and 1076 were downregulated in nm2. BLASTGO analysis showed that these differentially expressed genes were involved in various biological processes, cellular components and molecular functions. KEGG analysis indicated an enrichment of these differentially expressed genes in 240 pathways, including metabolic pathways, pancreatic secretion, protein digestion and absorption, fat digestion and absorption and glycerolipid metabolism. To verify the accuracy of the DGE results, quantitative reverse transcription PCR (qRT-PCR) was performed, focusing on key genes in several related pathways, and the results were highly consistent with the DGE results. Our findings indicated significant differences in cuticular protein genes, ecdysone biosynthesis genes and ecdysone-related nuclear receptors genes, but no significant difference in juvenile hormone and chitin biosynthesis genes was detected. Our research findings lay the foundation for further research on the formation mechanism of the nm2 mutant.

Recent development in ecdysone receptor of crustaceans: current knowledge and future applications in crustacean aquaculture

“…The schematic figure was created with permission using free sample Motifolio PPT Illustration Toolkit (Motifolio Inc, Ellicott City, MD, USA; www.motifolio.com). Modified from (Hwang et al 2016; Puthumana et al 2017; Wang et al 2017; Hyde et al 2019).…”

“…The notion of the puffing activities has led to the expression of early genes that encodes several transcription factors such as Broad , ecdysone‐inducible gene ( E74 , E75 , and E93 ), and hormone receptor‐like in 39 ( HR39 ), followed by the activation of early‐late ecdysone‐induced NR genes, such as ecdysone‐inducible gene E78 and hormone receptor‐like in 3/4/38 ( HR3 , HR4 , and HR38 ). Lastly is the downstream transcription of the late genes by early‐late genes, such as chitin biosynthesis genes, cuticular genes, and neuropeptide genes (Wang et al 2017). The late genes, directly and indirectly, regulate various moult‐related physiological processes, including development, growth and reproduction (Yao et al 2010).…”

“…The late genes, directly and indirectly, regulate various moult‐related physiological processes, including development, growth and reproduction (Yao et al 2010). At this step, the signals of the late genes are amplified via the synergistic action of FTZ transcription factor 1 (FTZ‐F1) with EcR, in which the transcript level for both genes (of FTZ‐F1 and EcR ) increases simultaneously, especially during cuticle formation and eclosion hormone (Sultan et al 2014; Wang et al 2017). Therefore, the expression of EcR is highest during premoult stage (Huang et al 2015).…”

“…Cuticular protein genes (CPGs) are responsible for the development of epidermal protein structure (Nagasawa 2012) and other processes such as protection against virus infection (Yang et al 2018). According to a study by Wang et al (2017), the CPGs are regulated by HR3 and HR4 , and it has been shown that CPG10 may regulate cuticle pressure by activating the ecdysone biosynthesis process. Looking specifically at crustaceans, Zhang et al (2018) showed that the gene expressions of CHT and EcR were significantly upregulated during E. sinensis limb bud regeneration.…”