Developmental proteome dynamics of silk glands in the 5th instar larval stage of Bombyx mori L (CSR2 × CSR4)

Abstract Bivoltine breed of Bombyx mori ( B. mori ), CSR2 × CSR4 is an Indian high yielding silkworm strain. Silk gland proteome of this strain was not studied till now. Methods of improving silk production by chemical approaches have reached saturation and transgenic methods are needed in further to boost silk production. An understanding of proteomic changes during silk gland development helps in designing experiments to enhance silk production by transgenic approaches. The present study reports comprehensive developmental proteomic analysis of CSR2 × CSR4, 5th instar whole silk glands. Eighty six unique protein IDs were obtained from the analysis of one hundred and twenty protein spots. Among the identified proteins, majority of the proteins were involved in metabolism (41%) followed by proteins involved in protein homeostasis (30%). Sixty percent of the identified proteins showed dynamic nature by expression analysis from day 1, day 3, day 5 and day 7 gels. In comparison to the published data till now on silk gland proteomics this study reports identification of 20 new proteins from the silk glands for the first time. Significance The paper reports for the first time proteomic analysis of high yielding silkworm strain of India. The study analyzes whole silk glands to understand the tissue in total during 5th instar development. Lowering fibroin content made us to identify a large number of new proteins which were not reported till now in the silk gland proteome. Proteins which are involved in silk synthesis and release were found to be developmentally regulated. The study identified alanine, serine and glycine tRNA ligases for the first time and also showed their up-regulation on day 7 of 5th instar larval stage. The amino acid repeat of fibroin protein is enriched with the three amino acids, glycine, serine and alanine. The identified proteins could be studied further to understand their functional role in-depth.