The development of efficient germ-line transformation technologies for mosquitoes has increased the ability of entomologists to find, isolate and analyze genes. The utility of the currently available systems will be determined by a number of factors including the behavior of the gene vectors during the initial integration event and their behavior after chromosomal integration. Post-integration behavior will determine whether the transposable elements being employed currently as primary gene vectors will be useful as gene-tagging and enhancertrapping agents. The post-integration behavior of existing insect vectors has not been extensively examined. Mos1 is useful as a primary germ-line transformation vector in insects but is inefficiently remobilized in Drosophila melanogaster and Aedes aegypti. Hermes transforms D. melanogaster efficiently and can be remobilized in this species. This element is also useful for creating transgenic A. aegypti, but its mode of integration in mosquitoes results in the insertion of flanking plasmid DNA. Hermes can be remobilized in the soma of A. aegypti and transposes using a common cut-and-paste mechanism; however, the element does not remobilize in the germ line. piggyBac can be used to create transgenic mosquitoes and occasionally integrates using a mechanism other than a simple cut-and-paste mechanism. Preliminary data suggest that remobilization is infrequent. Minos also functions in mosquitoes and, like the other gene vectors, appears to remobilize inefficiently following integration. These results have implications for future gene vector development efforts and applications.

The post-integration activity of piggyBac transposable element gene vectors in Aedes aegypti mosquitoes was tested under a variety of conditions. The embryos from five independent transgenic lines of Ae. aegypti, each with a single integrated non-autonomous piggyBac transposable element gene vector, were injected with plasmids containing the piggyBac transposase open-reading frame under the regulatory control of the Drosophila melanogaster hsp70 promoter. No evidence for somatic remobilization was detected in the subsequent adults whereas somatic remobilization was readily detected when similar lines of transgenic D. melanogaster were injected with the same piggyBac transposase-expressing plasmid. Ae. aegypti heterozygotes of piggyBac reporter-containing transgenes and piggyBac transposase-expressing transgenes showed no evidence of somatic and germ-line remobilization based on phenotypic and molecular detection methods. The post-integration mobility properties of piggyBac in Ae. aegypti enhance the utility of this gene vector for certain applications, particularly those where any level of vector remobilization is unacceptable.

The cinnabar gene of Drosophila melanogaster (Meigen) encodes for kynurenine hydroxylase, an enzyme involved in ommochrome biosynthesis. This gene is commonly included as a visible genetic marker in gene vectors used to create transgenic Aedes aegypti (L.) that are homozygous for the khw allele, the mosquito homolog of cinnabar. Unexpectedly, the phenotype of cells expressing kynurenine hydroxylase in transgenic Ae. aegypti is cell autonomous as demonstrated by the recovery of insects heterozygous for the kynurenine hydroxylase transgene with mosaic eye color patterns. In addition, a transgenic gynandromorph was recovered in which one-half of the insect was expressing the kynurenine hydroxylase transgene, including one eye with red pigmentation, whereas the other half of the insect was homozygous khw and included a white eye. The cell autonomous behavior of cinnabar in transgenic Ae. aegypti is unexpected and increases the utility of this genetic marker.