Location: Tick and Biting Fly Research
Project Number: 6205-32000-031-36
Start Date: Oct 01, 2011
End Date: Sep 30, 2012
There are a number of documents that are available on risk assessment of transgenic insects. The report from the IAEA/FAO meeting in 2002 is widely known and often cited. More recently, many in the field have been involved in making a report for the European Food Safety Authority (EFSA), which was published in 2010. This is probably the most thorough document in the area. Also relevant is the USDA environmental risk assessment for field release of transgenic pink bollworm and fruit flies. Some of the potential risks identified in the EFSA document were not addressed in the USDA report, e.g., the risk of horizontal gene transfer of piggyBac elements and the likelihood that a transgenic insect would have increased fitness. We will address the following potential risks in this proposal: 1) Risk: as RIDL is based on a single-lethal gene, there is the potential for development of early resistance. This is analogous to an insecticide that has a single mode of action. Evaluation approach: Raise transgenic strain in relatively large numbers without tetracycline and measure the frequency of resistant females. Determine if resistance is heritable. We also will propose to make a transgenic strain that has two independent lethal genes. 2) Risk: The transgene is unstable and can jump to other species (i.e., horizontal gene transfer). In practice, it has proved very difficult to remobilize piggyBac transgenes. Evaluation approach: Raise the strain for several generations and determine if transgene is lost or remobilizes, i.e., perform Southern blot hybridization and inverse PCR. We also propose to deliberately try to remobilize the transgene by injection of DNA that encodes transposase. We propose to engineer a strain that has only one end of a piggyBac transposon. That would essentially make it impossible for the transgene to jump. 3) Risk: the transgenic strain may mate with a related species and thus transfer the transgene (i.e., hybridization). Evaluation: Analyze mating behavior of transgenic males compared to wild type males. Determine if transgenic males can compete effectively with wild type males. Determine if transgenic males will mate with females from a related species: Cochliomyia macellaria. 4) Risk: Transgenic screwworm strain shows abnormal environmental interaction with predators and parasitoids. Evaluation: Compare interaction of transgenic and non-transgenic screwworm with known predators and parasitoids.