Developmental and transcriptomic features characterize defects of silk gland growth and silk production in silkworm naked pupa mutant. (August 2019)

• Record Type: Journal Article
• Authors: Hu, Wenbo; Chen, Yulin; Lin, Ying; Xia, Qingyou
• Is Part Of: Insect biochemistry and molecular biology. Volume 111(2019)
• Publication Date: 2019-08
• Subjects: Silkworm -- Silk gland degeneration -- Fibroin secretion-deficiency -- Cellular stress responses -- Naked pupa mutant -- Transcriptome; Nd naked pupa -- L5D3 the 3rd day of the fifth larval instar -- ASG anterior silk gland -- MSG middle silk gland -- PSG posterior silk gland -- FPKM fragments per kilobase of transcript sequence per millions base pairs sequenced -- KEGG Kyoto Encyclopedia of Genes and Genomes -- FibH fibroin heavy chain -- FibL fibroin light chain -- CT C terminal domain -- ER endoplasmic reticula -- Go the Golgi apparatus; Insect biochemistry -- Periodicals; Insects -- Physiology -- Periodicals; Insects -- Molecular aspects -- Periodicals; Biochemistry -- Periodicals; Insectes -- Biochimie -- Périodiques; Insectes -- Composition -- Périodiques; Insectes -- Physiologie -- Périodiques; Insectes -- Aspect moléculaire -- Périodiques; Biochimie -- Périodiques; Biochemistry; Insect biochemistry; Insects -- Molecular aspects; Insects -- Physiology; Periodicals; 572.8157
• DOI: 10.1016/j.ibmb.2019.05.010
• Languages: English
• ISSNs: 0965-1748

Abstract

Abstract: The silkworm Bombyx mori is a well-characterized model organism for studying the silk gland development and silk production process. Using positional cloning and gene sequencing, we have previously reported that a truncated fibroin heavy chain was responsible for silkworm naked pupa ( Nd ) mutant. However, the mechanisms by which the mutant FibH causes developmental defects and secretion-deficiency of the silk gland remain to be fully elucidated. Here, silk gland's developmental features, histomorphology, and transcriptome analyses were used to characterize changes in its structure and gene expression patterns between Nd mutant and WT/Dazao. Whole larval stage investigation showed that Nd -PSG undergoes an arrested/delayed development, which eventually resulted in a gland degeneration. By using section staining and transmission electron microscope, a blockade in intracellular vesicle transport from endoplasmic reticulum to Golgi apparatus (secretion-deficiency) and an increased number of autophagosomes and lysosomes were found in Nd -PSG's cytoplasm. Next, by using RNA sequencing and comparative transcriptomic analysis, 2178 differentially expressed genes were identified between Nd -PSG and WT-PSG, among which most of the DEGs associated with cellular stress responses (autophagy, ubiquitin-proteasome system, and heat shock response) were significantly up-regulated in Nd -PSG, suggesting that mutant FibH perturbed cellular homeostasis and resulted in an activation of adaptive responses in PSG cells. These findings reveal the molecular mechanism of the Naked pupa ( Nd ) mutation and provide insights into silk gland development as well as silk protein production in silkworm Bombyx mori . Graphical abstract: Image 1 Highlights: Posterior silk gland of the naked pupa mutant ( Nd -PSG) underwent an arrested/delayed development. The 1st day of the fourth larval instar (L4D1) represented a key stage during silk gland development. Distended endoplasmic reticula and poorly developed Golgi apparatus were responsible for fibroin secretion deficiency. Secretion-deficient FibH was cytotoxic and perturbs cellular homeostasis. Molecular mechanism of the Naked pupa ( Nd ) mutation was described.