Abstract
Background: The silkworm (Bombyx mori) is an important lepidopteran model insect worldwide which undergoes a complete metamorphosis developmental process. Although genome sequencing has been long performed, no transcriptome data covering the complete life cycle are available. Methods: Herein, a total of 10 samples were collected consecutively at four different developmental stages, including eggs of 24 h after oviposition (Ed) and eggs of 24 h after artificial egg-hatching (E); larvae from fist to fifth instar (L1–L5); early and late pupa (P4 and P8); and adult moth (M), were subjected to Illumina RNA-Seq and time-course analysis. Results: The summations of the gene expression of the silkworm ten developmental stages show: at Ed stage, eggs develop towards diapause status, the total gene expression level is relatively low; at E stage, after artificial egg-hatching, the expression level improves rapidly; during larval stages from L1–L5, the expression level rises gradually and reaches a peak at L5 stage; during pupae and moth stages, the total gene expression decline stage by stage. The results revealed a dynamical gene expression profile exhibiting significant differential expressions throughout the silkworm life cycle. Moreover, stage-specific key genes were identified at different developmental stages, suggesting their functions mainly characterized in maintaining insect development and immunity homeostasis or driving metamorphosis. GO annotation and KEGG enrichment analysis further revealed the most significantly enriched and fundamentally biological processes during silkworm growth. Conclusion: Collectively, our omics data depicted the first comprehensive landscape of dynamic transcriptome throughout complete developmental processes of B. mori. Our findings also provide valuable references and novel insights into understanding the molecular developmental remodeling events for other Lepidoptera species.
Highlights
The silkworm, Bombyx mori (B. mori), is one of the most economically important insects in the sericulture industry, which has a long history of more than 5000 years of domestication [1]
The early larval stage, in which the larvae are fed on raw mulberry leaves, is followed by three distinct pupal stages and by the adult moth that emerges from its cocoon after about two weeks
The life cycle of silkworm is characterized by a series of developmental events, and the transcriptome of each developmental stage has different functions and biological meanings
Summary
The silkworm, Bombyx mori (B. mori), is one of the most economically important insects in the sericulture industry, which has a long history of more than 5000 years of domestication [1]. The human macular carotenoid transporter (HMCT) was first discovered based on research achievements of B. mori carotenoid transporter system (BCTS) derived from silkworm yellow-cocoon strain [3]. Another case is that silkworm has advantages as a model organism in toxicological research including health safety and environmental pollution assessment, mainly due to their high sensitivity to chemical compounds such as pesticides, drugs, and heavy metals [4]. Due to the lack of studies on silkworm developmental stages such as, egg, larva, pupa, and moth causes limitations on understandings of silkworm growth and cultivation in sericulture industrial practice
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