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, the workhorse of D. melanogaster molecular genetics, has a pronounced nonrandom insertion spectrum. It has been estimated that 87% saturation of the approximately 13,500-gene complement of D. melanogaster might require generating and analyzing up to 150,000 insertions. We describe specific improvements to the lepidopteran transposon piggyBac 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.

Interpreting results from field deployments of semipermeable membrane devices.

Three canisters of semipermeable membrane devices (SPMDs), each containing five SPMDs, were deployed at three different locations on a transect across a small river removed from the impact of near-field point sources. Following a 62-day deployment, the masses of various polynuclear aromatic hydrocarbons (PAH) sequestered by each SPMD in each canister were determined. The compound-specific mean residues (ng/SPMD) obtained for the PAHs with pK(ow) values >4.4 showed statistically significant (alpha = 0.10) differences between the three deployment locations (canisters) ranging from approximately 10 to 160 ng/SPMD, corresponding to relative percent differences (RPDs) ranging from 10% to 54%. There were no statistically significant differences between the same three locations for the single PAH with a pK(ow) <4.4. A detailed discussion of how different (uncontrollable) environmental variables may have impacted the experimental results is provided to illustrate the uncertainties associated with interpreting the results from SPMD field deployments and highlight the need for some means of correcting for these impacts. The results from this work also illustrate the need to account for spatial variability in water column concentrations (i.e., sample heterogeneity) as part of any interpretation.