New genetic tools for Improving SIT in Ceratitis capitata: embryonic lethality and sperm marking

Institute of Zoology and Anthropology, Georg-August-University Göttingen, 37077, Göttingen, Germany

ABSTRACT Environment friendly sterile insect technique (SIT) is being applied effectively as a component of area-wide integrated pest management (AW-IPM) for Ceratitis capitata since 1970s. Nevertheless improved biological strategies are needed to increase the efficacy of AW-IPM. Transgenic approaches should increase and widen the applicability of such programmes to different pest species. In this respect two major strategies are followed: First an approach to cause sterility was designed without interfering with spermatogenesis to maintain males and their sperm as competitive as possible. We followed a strategy, which is based on the expression of a lethal factor under the control of a promoter that is active at early blastoderm stages. The system employs the ectopic expression of a hyperactive proapoptotic gene that causes embryo-specific lethality when driven by the tetracycline-controlled transactivator tTA under the regulation of a cellularization gene enhancer/promoter. The system has been tested successfully in Drosophila melanogaster (Horn & Wimmer 2003). We tried the direct transfer of the Drosophila system to Ceratitis capitata by injecting the respective constructs that carry Drosophila-derived promoters. Unfortunately, the cellularization specific promoters from Drosophila seem not functional in Ceratitis. Therefore, the corresponding enhancers/promoters from Ceratitis were isolated and subsequently the tTA was brought independently under the control of each enhancer/promoter region. These constructs were injected in Ceratitis for further evaluation. Second, we have engineered a medfly strain carrying a sperm marking system. This strain carries two fluorescent markers. One (turboGFP) marker is under the control of the spermatogenesis specific b2-tubulin promoter from Ceratitis and is therefore sperm specifically expressed. The second (DsRed) is under the control of the polyubiquitin promoter of Drosophila. Released males from this strain could be distinguished from wildtype males in the monitoring process. In addition, monitoring of the mating success of released sterile and fluorescently sperm-marked males by trapping females and examine their spermathecae would be possible. This effective and easily recognizable sperm marking will make novel studies possible on medfly reproductive biology and using sperm marked strains could optimize releasing strategies in SIT-based AW-IPM.

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    ABSTRACT: The establishment of broadly applicable insect transgenesis systems will enable the analyses of gene function in diverse insect species. This will greatly increase our understanding of diverse aspects of biology so far not functionally addressable. Moreover, insect transgenesis will provide novel strategies for insect pest management and the means to impair transmission of pathogens by human disease vectors. Especially the Sterile Insect Technique (SIT) might be improved by the use of transgenic approaches. The SIT represents an effective and ecologically safe method for area-wide pest control that reduces the pest population by mass release of sterilized organisms, leading to infertile matings and in consequence to a decline of the pest population. Although the SIT is already successfully applied for some species, each of its steps – mass-rearing, sex-separation for male-only releases, sterilization, and marking for monitoring – can be improved biotechnologically to optimize the efficiency and to reduce the costs of ongoing programs or to transfer this effective technique to a wider range of species. However, this powerful transgenic technology must be applied with great care to avoid harm to our environment. KeywordsTransposable elements-Pest management-GMO safety
    12/2010: pages 169-194;
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    ABSTRACT: The application of the Sterile Insect Technique (SIT) in area-wide integrated pest management (AW-IPM) programmes continues to increase. However, programme efficiency can still be considerably enhanced when certain components of the technology are improved, such as the development of improved strains for mass rearing and release. These include strains that (1) produce only male insects for sterilization and release and (2) carry easily identifiable markers to identify released sterile insects in the field. Using both classical and modern biotechnology techniques, key insect pests are targeted, where SIT programmes are being implemented. The pests include mosquitoes, the Mexican fruit fly, the codling moth, the oriental fruit fly and the pink bollworm. This special issue summarizes the results of research efforts aimed at the development and evaluation of new strains to a level where a decision can be made as to their suitability for use in large scale SIT programmes. Major beneficiaries will be operational AW-IPM programmes that apply the SIT against major insect pests.
    Genetica 01/2011; 139(1):1-5. DOI:10.1007/s10709-010-9543-z · 1.75 Impact Factor

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