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ARS Home » Plains Area » Kerrville, Texas » Knipling-Bushland U.S. Livestock Insects Research Laboratory » LAPRU » Research » Research Project #433372

Research Project: Developing a Genetic Sexing Strain of Screwworms with Early Mortality to Females

Location: Livestock Arthropod Pests Research

Project Number: 3094-32000-038-36-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 16, 2017
End Date: Aug 31, 2019

Objective:
The objective of this work is to improve upon the current genetic sexing system with 100% female lethality late in development. The goal is to develop a strain with 100% early (egg or young larvae) female lethality. If sufficient resources exist, the next objective will be to evaluate the strain for its characteristics under under mass rearing conditions, its ability to eliminate a wild population under laboratory conditions (proof-of-concept study), its competitiveness and behavior in semi-field trials, and determine if it meets all environmental safety requirements.

Approach:
Make transgenic screwworms with the most promising “driver” (DR) and “effector” (EF) gene constructs using genetic material first tested and proven in green blow fly (model insect used at N.C. State Univ.). Perform lethality tests by crossing DR and EF lines on diet that lacks tetracycline. If necessary, modify the gene constructs to achieve higher expression of the cell death genes in NWS. 2. Make “double homozygous” (double component) screwworm lines that carry the most effective combinations of DR and EF. Confirm high female lethality is at the embryo stage and is tetracycline repressible. 3. Make “all-in-one” genetic systems that contain DR and EF in one construct. Evaluate in green blow fly at NCSU and transfer most promising system to Panama where lines will be developed. 4. Do the same experiments as previously for the single component system with the double component and all-in-one lines, which include: overall fitness including egg production, egg hatch, biological yield and longevity; mating compatibility and competitiveness compared to ‘wild-type’ screwworms; potential for out-crossing to related flies; determining the influence of genetic background and; molecular characterization of the double component line. 5. Do proof-of-concept (consist of eliminating a ‘wild-type’ population in large cage, laboratory study) and small-scale field release of the double component line to show usefulness to the Eradication and Prevention Program. 6. Present the ‘best’ line to the Technical Direction of COPEG (Panama-U.S. Commission for Eradication and Prevention of Screwworms) for training in rearing the line and to evaluate the line under pseudo-mass rearing conditions. 7. Complete gene annotation and refine screwworm genome assembly by using approaches such as 10 X genomic, HiC and linkage mapping. This will provide needed information for more efficient development of transgenic lines.