Identification of Diapause and Non-diapause Associated Proteins in the Eggs of Multivoltine Silkworm Bombyx mori by MALDI MS Analysis

The diapause and non diapause associated proteins of multivoltine silkworm eggs were analysed by two dimensional (2D) gel electrophoresis. The study was made at 0 hr, 24 hrs and 48 hrs after oviposition. A total of four protein spots in diapause eggs at 24 hrs of oviposition and two protein spots in non diapause eggs at 0 hrs of oviposition were observed. All the six protein spots were considered to have association with diapause and non diapause characters. The molecular weight (MW) and isoelectric point (PI) of these 6 protein spots were calculated. The protein spots 1 and 2 observed in 0 hr of non diapause eggs were found to have the MW of 67 and 75 KDa and PI of 8.6 and 8.4 respectively. Similarly the four protein spots observed in diapause egg at 24 hrs of oviposition exhibited MW viz., 15, 17,20 and 25 KDa and PI of 5.3, 5.8, 6.5 and 6.0 respectively. All these 6 identified protein spots were subjected to in-gel digestion and resulted tryptic peptides were analyzed by Matrix-assisted laser desorption/ionization time-of flight mass spectrometry (MALDI TOF-MS). Databases searched based on experimentally determined molecular weights of peptides for the determination of the identities of proteins. The identified proteins indicated homology of 34% to 95%. The results indicate that the proteins may playa role in development of diapause and non diapause eggs.