A complementary transposon tool kit for Drosophila melanogaster using P and piggyBac

With the availability of complete genome sequence for Drosophila melanogaster , one of the next strategic goals for fly researchers is a complete gene knockout collection. The P -element transposon 1 , the workhorse of D. melanogaster molecular genetics, has a pronounced nonrandom insertion spectrum 2 . It has been estimated that 87% saturation of the ∼13,500-gene complement of D. melanogaster 3 might require generating and analyzing up to 150,000 insertions 2 . We describe specific improvements to the lepidopteran transposon piggyBac 4 and the P element that enabled us to tag and disrupt genes in D. melanogaster more efficiently. We generated over 29,000 inserts resulting in 53% gene saturation and a more diverse collection of phenotypically stronger insertional alleles. We found that piggyBac has distinct global and local gene-tagging behavior from that of P elements. Notably, piggyBac excisions from the germ line are nearly always precise, piggyBac does not share chromosomal hotspots associated with P and piggyBac is more effective at gene disruption because it lacks the P bias for insertion in 5′ regulatory sequences.