Australian endemic pest tephritids: genetic, molecular and microbial tools for improved Sterile Insect Technique.
Bottom Line: Transcriptomes from various species, tissues and developmental stages, to aid in identification of manipulation targets for improving SIT, have been assembled and are in the pipeline.Broad analyses of the microbiome have revealed a metagenome that is highly variable within and across species and defined by the environment.More specific analyses detected Wolbachia at low prevalence in the tropics but absent in temperate regions, suggesting a possible role for this endosymbiont in future control strategies.
Among Australian endemic tephritid fruit flies, the sibling species Bactrocera tryoni and Bactrocera neohumeralis have been serious horticultural pests since the introduction of horticulture in the nineteenth century. More recently, Bactrocera jarvisi has also been declared a pest in northern Australia. After several decades of genetic research there is now a range of classical and molecular genetic tools that can be used to develop improved Sterile Insect Technique (SIT) strains for control of these pests. Four-way crossing strategies have the potential to overcome the problem of inbreeding in mass-reared strains of B. tryoni. The ability to produce hybrids between B. tryoni and the other two species in the laboratory has proved useful for the development of genetically marked strains. The identification of Y-chromosome markers in B. jarvisi means that male and female embryos can be distinguished in any strain that carries a B. jarvisi Y chromosome. This has enabled the study of homologues of the sex-determination genes during development of B jarvisi and B. tryoni, which is necessary for the generation of genetic-sexing strains. Germ-line transformation has been established and a draft genome sequence for B. tryoni released. Transcriptomes from various species, tissues and developmental stages, to aid in identification of manipulation targets for improving SIT, have been assembled and are in the pipeline. Broad analyses of the microbiome have revealed a metagenome that is highly variable within and across species and defined by the environment. More specific analyses detected Wolbachia at low prevalence in the tropics but absent in temperate regions, suggesting a possible role for this endosymbiont in future control strategies.
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Mentions: Elimination of either tra or tra-2 by RNAi early in development disrupts the mechanism favouring female-specific splicing of tra and dsx in C. capitata, B. oleae and Anastrepha spp. [69,70,72-74] and leads to the expression of dsxM and the consequent development of male somatic tissue . Preliminary assessment of tra and tra-2 in B. tryoni (Bttra and Bttra-2) suggests the same functionality. Injection of full-length Bttra-2 and partial Bttra dsRNA fragments into B. tryoni embryos of 3h and 7h AEL was performed (Figure 5), with seven intersexes recovered from Bttra-2 injections into 7h embryos suggesting incomplete phenotypic conversion. Complete conversion resulted from Bttra injections of 3h embryos, whereby two phenotypic males developed that sired all female offspring when mated to a normal female (Figure 5). Thus, either gene can independently induce sex reversal and both genes may also be useful targets for transgenic RNAi in this species. Concommitant injections of buffer showed only marginally higher pupation rates than injections with dsRNA fragments suggesting physical handling was the greatest influence on the resultant numbers of emerged adults.