ATTEMPT AT TRANSGENESIS OF THE SILKWORM (BOMBYX-MORI L) BY EGG-INJECTION OF FOREIGN DNA

We analysed the feasibility of transforming the silkworm germ line cel ls by random insertion of foreign DNA. Cloned DNA, either supercoiled or linear, introduced into eggs at early stages of development was sub mitted to intense degradation after injection, but a stable pool of in tact sequences persisted throughout embryogenesis in both embryonic an d nonembryonic tissues. Screenings of germ line transformants were car ried out by tracking injected foreign sequences in genomic DNA of indi viduals at the GO and G1 generations. One case of germ line transmissi on of foreign DNA was observed among more than 500 broods analysed. Di stribution of the transgene among G1 individuals agrees with Mendelian inheritance from the GO to the G1 generation. The integrated sequence was modified compared to the originally injected one. This study show s that foreign DNA can integrate into the chromosomes of the silkworm germ lineage but that improving the method of making transgenics requi res the development of gene vector systems.