Developmental regulation of silk protein P25 in the silkworm Bombyx mori.

ABSTRACT

P25 protein was extracted from cocoons of the silkworm Bombyx mori by alkali solubilization and purified by gel elution. The purity and authenticity of the protein were confirmed by SDS-PAGE, 2-dimensional gel electrophoresis and peptide mapping. Polyclonal anti-P25 sera were raised in rabbit and mice. The relative abundance of P25 protein present in the larva during different developmental stages was analysed by SDS-PAGE, and quantified by sandwich ELISA. The minimum level (0·2 μg/animal) of this protein was recorded at the beginning of the first instar and maximum (16·7mg/pair of silkgland) on the final day of the V instar. During each moult period, P25 protein level was suppressed; the level increased with the initiation of feeding and reached maximum on the 3rd day of each instar except the final instar where the maximum was recorded prior to pupal moult. Western blot analysis also confirmed the developmental stage-specific accumulation of P25 protein in the silkworm Bombyx mori.