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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Insect Behavior and Biocontrol Research » Research » Research Project #429847

Research Project: Assessment and Mitigation of Genetic Breakdown of Transgenic Conditional Lethality Systems in Insect Species

Location: Insect Behavior and Biocontrol Research

Project Number: 6036-22000-030-08-I
Project Type: Interagency Reimbursable Agreement

Start Date: Sep 1, 2015
End Date: Aug 31, 2019

Objective:
The sterile insect technique (SIT) provides the most ecologically sound and efficient means for suppression of insect pest populations, but mass-rearing efficiency may be improved by eliminating females before male release, and improving mating competitiveness of sterilized males. Genetic manipulation of species subject to SIT, now allows the use of tetracycline-suppressible conditional lethality and sterility strategies to overcome both limitations. Our goal is to develop new transgenic strains for the fruit fly pests, Anastrepha (A.) ludens and Drosophila (D.) suzukii, for Tet-off female-specific embryonic lethality for sexing, and spermatocyte-specific lethality for male gonadal sterility. In combination, flies reared on Tet-free diet should result in only sterile male survivors for release. These strains, however, will be subject to genetic breakdown due to lethal effect mutations, and to evaluate this possibility, a D. suzukii lethality strain will be reared under large-scale conditions to quantify lethal revertants that survive on Tet-free diet. To prevent revertant survival a secondary temperature-dependent lethal system (DmDTS7) will be integrated into the Tet-off D. suzukii strain to assess survival under permissive and restrictive conditions. The sexing/sterility strains of A. ludens and D. suzukii will then be evaluated for mass rearing efficiency and mating competitiveness, and comparison to existing lines developed by classical genetic and/or symbiont based approaches. We expect these studies to promote the field release of transgenic strains having both enhanced efficiency and safety.

Approach:
Transgenic strains for Anastrepha (A.) ludens and Drosophila (D.) suzukii will be created using driver and lethal effector constructs for Tet-off embryonic uni-sex lethality. Optimal strains will be mated to create hybrid driver/effector strains that will be tested for male-sterility (based on survivial of progeny) on Tet and Tet-free diet. A D. suzukii uni-sex lethality strain will be reared under large-scale conditions to quantify larval lethal revertants (survivors on Tet-free diet), whose transgenes will be analyzed for possible mutations, or for second-site modifications. A dual conditional lethality strain will created in D. suzukii by insertion of the DmProsß21 (DTS-7) dominant temperature-sensitive mutant gene into a uni-sex Tet-off lethality strain by phiC3-mediated recombination, with the lethal systems tested individually and in concert under permissive (Tet-diet at 24ºC) and restrictive (Tet-free diet at 29ºC) conditions, and under large scale rearing.