A Blueprint of Microstructures and Stage-Specific Transcriptome Dynamics of Cuticle Formation in Bombyx mori

Abstract

Insect cuticle is critical for the environmental adaptability and insecticide resistance of insects. However, there is no clear understanding of the structure and protein components of the cuticle during each developmental stage of holometabolous insects, and knowledge about the protein components within each layer is vague. We conducted serial sectioning, cuticular structure analysis, and transcriptome sequencing of the larval, pupal, and adult cuticles of Bombyx mori. The deposition processes of epicuticle, exocuticle, and endocuticle during larval, pupal, and adult cuticle formation were similar. Transcriptome analysis showed that these cuticle formations share 74% of the expressed cuticular protein (CP) genes and 20 other structural protein genes, such as larval serum protein and prisilkin. There are seven, six, and eleven stage-specific expressed CP genes in larval, pupal, and adult cuticles, respectively. The types and levels of CP genes may be the key determinants of the properties of each cuticular layer. For example, the CPs of the RR-2 protein family with high contents of histidine (His) are more essential for the exocuticle. Functional analysis suggested that BmorCPAP1-H is involved in cuticle formation. This study not only offers an in-depth understanding of cuticle morphology and protein components but also facilitates the elucidation of molecular mechanisms underlying cuticle formation in future studies.

The BTB-ZF gene Bm-mamo regulates pigmentation in silkworm caterpillars

“…These findings suggested that the 32 CP genes are indispensable and that other CP genes may have redundant and complementary functions ( Pan et al, 2018 ). Previous studies revealed that the construction of the larval cuticle of silkworms requires the precise expression of more than two hundred CP genes ( Yan et al, 2022 ). The production, interaction, and deposition of CPs and pigments are complex and precise processes, and our research showed that Bm-mamo plays an important regulatory role in this process in silkworm caterpillars.…”

“…In addition to pigment synthesis, the microstructure/nanostructure of the body surface and wing scales are important factors that influence body color patterns. The body surface and wing scales of Lepidoptera are composed mainly of cuticular proteins (CPs) ( Liu et al, 2021 ; Yan et al, 2022 ). There are multiple genes encoding CPs in Lepidopteran genomes.…”

The BTB-ZF geneBm-mamoregulates pigmentation in silkworm caterpillars

“…These findings suggested that the 32 CP genes are indispensable and that other CP genes may have redundant and complementary functions ( 76 ). In previous studies, it was found that the construction of the larval cuticle of silkworms requires the precise expression of more than two hundred CP genes( 22 ). The production, interaction, and deposition of CPs and pigments are complex and precise processes, and our research showed that Bm-mamo plays an important regulatory role in this process in silkworm caterpillars.…”

“…In addition to pigment synthesis, the microstructure/nanostructure of the body surface and wing scales are important factors that influence body color patterns. The body surface and wing scales of Lepidoptera are mainly composed of cuticular proteins (CPs) ( 21, 22 ). There are multiple genes encoding CPs in Lepidopteran genomes.…”

Genome‐wide identification of cuticle protein superfamily in Frankliniella occidentalis provide insight into the control of both insect vectors and plant virus

“…The CPG family features multiple GGYGG or GGxGG repeats (Futahashi et al, 2008), and the CPCFC family contains two or three repetitive C‐X5‐C motifs (Ioannidou et al, 2014). These comprehensive classifications offer better understanding of the diversity and complexity within insect CPs, shedding light on their essential roles in the intricate biology of insects (Yan et al, 2022).…”