Genetic transformation of the silkworm, Bombyx mori, with Autographa californica nuclear polyhedrosis virus

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Firefly luciferase gene which is expressed under control of Drosophila melanogaster heat shock protein gene promoter was introduced into Autographa californica nuclear polyhedrosis virus (AcNPV). When the 5th instar larvae of the silkworm, Bombyx mori, were inoculated with the recombinant virus, luciferase activities were detected in the virus-infected larvae and pupae. The luciferase activities were also detected in the newly hatched larvae at the next generation (F_1) and the hatched larvae were reared until the further next generation (F_2). The genomic DNAs were extracted from the silkworm larvae of F_1 and F_2 generation and used as template for the polymerase chain reaction (PCR) using 5' and 3' DNA primer of luciferase gene. PCR amplification and Southern blot hybridization analysis demonstrated that luciferase gene was transmitted until at least F_2 generation. The luciferase gene was transmitted accoording to Mendelian inheritance. The V-cathepsin gene encoding a cathepsin-like cysteine protease of AcNPV was also detected from all individuals of the F_2 generation, indicating that trasnovarian transmission of AcNPV DNA occurred in the silkworm, B.mori. These results showed that AcNPV could be utilized as vector for the transovarian transmission of foreign genes in the silkworm.These are the first results to our knowledge on the transmission of foreign genes through generations in the insect except for D.melanogaster.