DEVELOPMENTAL REGULATION OF SILK PROTEIN P-25 IN THE SILKWORM BOMBYX-MORI

P-25 protein was extracted from cocoons of the silkworm Bombyx mori by alkali solubilization and purified by gel elution. The purity and aut henticity of the protein were confirmed by SDS-PAGE, 2-dimensional gel electrophoresis and peptide mapping. Polyclonal anti-P-25 sera were r aised in rabbit and mice. The relative abundance of P-25 protein prese nt in the larva during different developmental stages was analysed by SDS-PAGE, and quantified by sandwich ELISA. The minimum level (0.2 mu g/animal) of this protein was recorded at the beginning of the first i nstar and maximum (16.7 mg/pair of silkgland) on the final day of the V instar. During each moult period, P-25 protein level was suppressed; the level increased with the initiation of feeding and reached maximu m on the 3rd day of each instar except the final instar where the maxi mum was recorded prior to pupal moult. Western blot analysis also conf irmed the developmental stage-specific accumulation of P-25 protein in the silkworm Bombyx mori.