Author
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Handler, Alfred - Al |
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SCHETELIG, MARC - Former ARS Employee |
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Submitted to: Book Chapter
Publication Type: Book / Chapter Publication Acceptance Date: 9/16/2013 Publication Date: N/A Citation: N/A Interpretive Summary: The creation of genetically transformed, or transgenic, strains of economically important insects for the development of more effective biological control programs is a major goal of the USDA, Agriculture Research Service, Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, Florida. Development of this methodology and strategies to effectively and safely utilize transgenic insects for biological control will depend upon a comprehensive knowledge of the mechanisms involved in transposon movement, the types of biocontrol strategies that transgenic strains can improve, and a critical analysis of potential risks involved in the release of transgenic insects. This chapter addresses the current knowledge of the transposable element vectors used to mediate germ-line transformation of tephritid fruit fly species. The potential use of genetically transformed strains to improve the sterile insect technique and for new strategies using conditional lethal transgenes for autocidal biological control is discussed. In addition, factors that affect stability of transposon vectors and methods to improve their stability after genomic integration are addressed in the context of the field release of these strains. New transformation vectors are described that allow targeting of transgenes into predefined acceptor sites in the genome, with stabilization facilitated by removal of vector sequences needed for mobility. This information will be used to facilitate the creation of effective and ecologically safe transgenic insects, as well as methods to test and assess these attributes. Technical Abstract: Tephritid fruit flies are among the most serious agricultural pests in the world, owing in large part to those species having broad host ranges including hundreds of fruits and vegetables. They are the largest group of insects subject to population control by a biologically-based systems, most notably the sterile insect technique (SIT). Given the needs for improved SIT, including visible markers for field detection, sexing systems for male-only strains and male sterilization, the possibility of achieving these improvements using genetically modified strains has been a long-standing goal. Thus, it is not surprising that the first report of a transposon-mediated germ-line transformation of a non-drosophilid insect species was for the tephritid, the Mediterranean fruit fly, Ceratitis capitata. The success of this transformation, after many attempts by several labs using the Drosophila P and hobo vector systems, was due largely to the use of the newly discovered and widely active Tc-related Minos element. But of equal importance for transformation of this species was the availability of a white eye (we) mutant host strain and the cloning of the medfly we+ allele that could be used as mutant rescue marker for transformant selection. This same marker system was then successfully used to transform medfly with the piggyBac and Hermes transposon vector systems. In subsequent years, at least five additional tephritid species have been transformed with piggyBac or Minos, though typically using the more widely applicable fluorescent protein (FP) markers. Together, germ-line transformation of tephritid species represent the largest number of species from a single family, which has been due in large part to the economic interest in these species and the relative ease of using methods and reagents for transgenesis that have been developed for Drosophila. |
