Electrophoretic Studies on Silk Gland Proteins of Philosamia Ricini

Silk is a biological fiber produced by the caterpillars of Philosamia ricini moths at the end of their larval phase. Silk glands of silkworm secrete two major classes of proteins, the fibroin fiber, protein and sericin glue protein. The cocoon of silkworm is mainly composed of these two proteins. The present study focused on the development of new inhibitory protein under the condition of low temperature. The gene, produce these proteins, express in fifth instar stage at 29 ± 2 ⁰ C and humidity 90 % i. e.  in normal rearing conditions. It is noteworthy that sericin show distinct bands on polyacrylamide gel electrophoresis, whereas fibroin did not. This suggests that components of sericin, but not fibroin, have definite molecular weights. Electrophoretic analysis of cold stressed silk gland protein in 12.5 % SDS – PAGE showed the development of new high molecular weight proteins in the cold stressed Philosamia ricini larvae when compared to control. Our results fulfills the aim of our study, which describes that when the fifth instar larvae of castor moth were acclimated to 4⁰ C for a few days, expression of two major proteins of silk gland  was hindered which were expressed in normal rearing conditions. In this case, emergence of new protein takes place comprising the molecular mass of more than 66 KDa.