Postintegration stability of the silkworm piggyBac transposon

• Created 135 transgenic silkworm lines using piggyBac [3 × p3 EGFP afm] vector.
• Screened a W chromosome-linked transgenic line inserted in a standard TTAA site.
• Cloned a specific sequence of the Bombyx mori W chromosome.
• Endogenous elements not affect the stability of inserted piggyBac in silkworm genome.

The piggyBac transposon is the most widely used vector for generating transgenic silkworms. The silkworm genome contains multiple piggyBac-like sequences that might influence the genetic stability of transgenic lines. To investigate the postintegration stability of piggyBac in silkworms, we used random insertion of the piggyBac [3 × p3 EGFP afm] vector to generate a W chromosome-linked transgenic silkworm, named W-T. Results of Southern blot and inverse PCR revealed the insertion of a single copy in the W chromosome of W-T at a standard TTAA insertion site. Investigation of 11 successive generations showed that all W-T females were EGFP positive and all males were EGFP negative; PCR revealed that the insertion site was unchanged in W-T offspring. These results suggested that endogenous piggyBac-like elements did not affect the stability of piggyBac inserted into the silkworm genome.

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