Comparative proteome analysis and thermal stress induced changes in the embryo of poly- and bi-voltine strains of Bombyx mori

Abstract

Proteins are the ultimate operating molecules producing the physiological effect in all the stages of an organism. As a consequence, proteome of the embryo play a pivotal role in determining the biological structures besides cellular organization and morphogenetic movements that occur during embryo development. But, changes in the environment temperature for few hours whether that alter the embryo development, protein expression and hatching of infants are unknown in Bombyx mori L. Hence, eggs of poly- and bi-voltine breeds were exposed to heat shock temperature of 35, 40 and 45°C for 2 h to measure tolerance level and differential expression of proteins in different age of the embryos. To facilitate comparative analysis among different breeds a comprehensive proteome map was constructed considering protein profile of different day’s embryos. Interestingly, ~10 to 21 protein bands were recorded during embryo development - from ovipostion till hatching - along with few new protein bands on day-6, which were differ in their intensity in different silkworm strains. Interestingly, no change in the protein pattern was observed in different days embryos exposed to thermal stress at 35 and 40°C. But degradation of 18 and 19 kDa proteins were recorded in all the days of embryos exposed to 45°C while four major protein bands remain unaltered. Further, the percent of hatching was slightly declined in 35 and 40°C and zero hatching was recorded in all the stages of eggs HS at 45°C. This clearly indicates that differential expression/degradation of proteins as a response to thermal stress not only influences the growth and development but also determine hatching of embryo. Accordingly, we suggest that embryonic protein map constructed in the present study shall be a valid reference for comparative analysis and hatching of embryos as one of the key traits to measure the rate of thermotolerance in the existing or new strains/breeds of B. mori.