Male-Biased Adult Production of the Striped Fruit Fly, Zeugodacus scutellata, by Feeding dsRNA Specific to Transformer-2

Sterile insect release technique (SIT) is effective for eradicating quarantine insects including various tephritid fruit flies. When SIT is used for fruit flies, it is challenging to remove females from sterile males due to oviposition-associated piercing damage. This study developed a sex transition technique by feeding double-stranded RNA (dsRNA) specific to a sex-determining gene, Transformer-2 (Zs-Tra2) of the striped fruit fly, Zeugodacus scutellata. Zs-Tra2 is homologous to other fruit fly orthologs. It is highly expressed in female adults. RNA interference (RNAi) of Zs-Tra2 by injecting or feeding its specific dsRNA to larvae significantly increased male ratio. Recombinant Escherichia coli cells expressing dsRNA specific to Zs-Tra2 were prepared and used to feed larvae to suppress Zs-Tra2 gene expression levels. When these recombinant bacteria were fed to larvae during the entire feeding stage, the test population was significantly male-biased. Some females treated with such recombinant E. coli exhibited mosaic morphological characters such as the presence of male-specific abdominal setae in females. This study proposes a novel technique by feeding dsRNA specific to Transformer-2 to reduce female production during mass-rearing of tephritid males for SIT.