Analyses of the Molecular Mechanisms Associated with Silk Production in Silkworm by iTRAQ-Based Proteomics and RNA-Sequencing-Based Transcriptomics

Silkworm
is used as a model organism to analyze two standard complex
traits, which are high and low silk yields. To understand the molecular
mechanisms of silk production, the posterior silk glands aged to the
third day of the fifth instar were analyzed from the ZB strain with
low silk production and from the control strain Lan10. Using isobaric
tags for relative and absolute quantification (iTRAQ) quantitative
shotgun proteomics and RNA-sequencing-based transcriptomics, 139 proteins
and 630 transcripts were identified as novel in the ZB strain compared
with the Lan10 strain, indicating that these results significantly
expand the coverage of proteins and transcripts of the posterior silk
glands in the silkworm. Of the 89 differently changed proteins, 23
were increased, and 66 were decreased. Of the 788 transcripts, 779
were upregulated, and 9 were downregulated. These results confirm
that decreased energy utilization/protein translation and enhanced
protein degradation are the key factors in lower silk production.
Moreover, this study provides novel insight into the molecular changes
that may result in lower silk production, namely, a combination of
impaired transcription activity, missed protein folding/transport,
and lowered yields of the main components of fibroin, along with weakened
growth/development of the posterior silk gland.