Attempt at Trangenesis of the Silkworm (Bombyx mori L.) by Egg-Injection of Foreign DNA

We analysed the feasibility of transforming the silkworm germ line cells by random insertion of foreign DNA. Cloned DNA, either supercoiled or linear, introduced into eggs at early stages of development was submitted to intense degradation after injection, but a stable pool of intact sequences persisted throughout embryogenesis in both embryonic and non-enbryonic tissues. Screenings of germ line transformants were carried out by tracking injected foreign sequences in genomic DNA of individuals at the G0 and G1 generations. One case of germ line transmission of foreign DNA was observed among more than 500 broods analysed. Distribution of the transgene among G1 individuals agrees with Mendelian inheritance from the G0 to the G1 generation. The integrated sequence was modified compared to the originally injected one. This study shows that foreign DNA can integrated into the chromosomes of the silkworm germ lineage but than improving the method of making transgenics requires the development of gene vector systems.