Induction of the white egg 3 mutant phenotype by injection of the double-stranded RNA of the silkworm white gene

Injection of double-stranded RNA (dsRNA) corresponding to the silkworm white gene (Bmwh3) into preblastoderm eggs of the wild-type silkworm induced phenotypes similar to those observed with mutants of the white egg 3 locus (10-19.6). The induced phenotypes were characterized by the presence of white eggs and translucent larval skin. Northern analysis showed that the expression of the endogenous Bmwh3 gene in the injected embryos was distinctly depressed. Furthermore, the injection of the GFP dsRNA inhibited the expression of the GFP gene from a plasmid co-injected with the dsRNA but did not depress the expression of the Bmwh3 gene. These findings demonstrate that sequence-specific RNA interference occurred in the silkworm. We conclude from the results that the RNA interference can be applied as a tool for the analysis of the gene function in the lepidopteran insects.