BIOLOGICALLY-BASED TECHNOLOGIES FOR MANAGEMENT OF CROP INSECT PESTS IN LOCAL AND AREAWIDE PROGRAMS
Location: Insect Behavior and Biocontrol Research Unit
Title: Transgenic sexing system for Ceratitis capitata (Diptera: Tephritidae) based on female-specific embryonic lethality
Submitted to: Journal of Insect Biochemistry and Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 29, 2012
Publication Date: January 3, 2013
Citation: Ogaugwu, C.E., Schetelig, M.A., Wimmer, E.A. 2013. Transgenic sexing system for Ceratitis capitata (Diptera: Tephritidae) based on female-specific embryonic lethality. Journal of Insect Biochemistry and Molecular Biology. 43:1-8.
Interpretive Summary: A major goal of our laboratory at the USDA, Agriculture Research Service, Center for Medical, Agricultural and Veterinary Entomology, USDA, Agricultural Research Service, Gainesville, FL is the development of biological control methods. This includes the use of transgenic technology to create strains of economically and medically important pest insect species. In this respect, development of effective and safe sexing strains for biological control has been shown to be important for the most successful biological control programs using the Sterile Insect Technique. Thus far, transgenic embryonic sexing systems have been developed in Drosophila melanogaster and in the Caribfly Anastrepha suspensa (at the Gainesville, FL laboratory).
Here we present new conditional sexing strains for the medfly, Ceratitis capitata. Based on previously evaluated genes, we tested the “best” components in the medfly to obtain sexing strains. An antibiotic added to the food can switch off the system during the rearing of the flies, allowing them to survive and reproduce. Under restrictive diet conditions without the antibiotic, all females die during a very early stage in development, which is important for large-scale production of a male-only population in mass rearing. Early female lethality during the fly development is important to prevent the costly consumption of larval diet, which can be as much as 30 tons a day. This study reports the first successful early acting sexing system in medfly.
Fruit fly pest species have been successfully controlled and managed via the Sterile Insect Technique (SIT), a control strategy that uses infertile matings of sterile males to wild females to reduce pest populations. Biological efficiency in the field is higher if only sterile males are released in SIT programs and production costs are also reduced. Sexing strains developed in the Mediterranean fruit fly Ceratitis capitata (medfly) through classical genetics are immensely beneficial to medfly SIT programs but exhibit reduced fertility and fitness, and transfer to other tephritid species is difficult. Transgenic approaches, which can possibly overcome the problems of classical genetic sexing strains (GSSs), have resulted in transgenic sexing strains (TSSs) based on dominant lethality mediated, however, mostly at pupal stages.
Here we present a transgene-based female-specific embryonic lethality system for embryonic sexing in medfly. The system utilizes the sex-specifically spliced transformer intron to restrict ectopic mRNA translation of the pro-apoptotic gene hidAla5 to only females when driven by a tetracycline-repressible transactivator gene tTA regulated by promoters/enhancers of cellularization genes. We have tested this system in the medfly C. capitata and, despite of observed position effects on the sex-specific splicing, we could establish the system as desired. After satisfactory performance in large-scale tests, TSSs from such a system will offer cost-effective sexing of pest insect strains once introduced into SIT programs and are straight forward to develop for other insect pest and vector species.