Comparative Proteomic Analysis of Posterior Silk Glands of Wild and Domesticated Silkworms Reveals Functional Evolution during Domestication

The wild silkworm Bombyx
mandarina was domesticated
to produce silk in China approximately 5000 years ago. Silk production
is greatly improved in the domesticated silkworm B. mori, but the molecular basis of the functional evolution of silk gland
remains elusive. We performed shotgun proteomics with label-free quantification
analysis and identified 1012 and 822 proteins from the posterior silk
glands (PSGs) of wild silkworms on the third and fifth days of the
fifth instar, respectively, with 128 of these differentially expressed.
Bioinformatics analysis revealed that, with the development of the
PSG, the up-regulated proteins were mainly involved in the ribosome
pathway, similar to what we previously reported for B. mori. Additionally, we screened 50 proteins with differential expression
between wild and domesticated silkworms that might be involved in
domestication at the two stages. Interestingly, the up-regulated proteins
in domesticated compared to wild silkworms were enriched in the ribosome
pathway, which is closely related to cell size and translation capacity.
Together, these results suggest that functional evolution of the PSG
during domestication was driven by reinforcing the advantageous pathways
to increase the synthesis efficiency of silk proteins in each cell
and thereby improve silk yield.