Maleness-on-the-Y (MoY) orthologue is a key regulator of male sex determination in Zeugodacus cucurbitae (Diptera: Tephritidae)

The initiation of sex differentiation in insects is regulated by primary sex determination signals. In the Medfly Ceratitis capitata and other Tephritids, Maleness-on-the-Y (MoY) is the master gene for male sex determination. However, the primary signal in Zeugodacus cucurbitae (Coquillett), a very destructive Tephritid pest across the world, remains ambiguous. In this study, we have isolated and characterized the Medfly MoY homolog in Z. cucurbitae, ZcMoY. ZcMOY protein shows high sequence conservation to its homologs in Bactrocera species. ZcMoY transcription begins and peaks at very early embryonic stages and then becomes undetectable except the testes and heads of day 1 male adults. Silencing ZcMoY in early embryos by RNAi causes abnormal external genitalia and interior reproductive organs, giving rise to intersexes and feminization of XY individuals. The expression pattern and knockdown phenotypes of ZcMoY indicate that ZcMoY plays a key role in regulating sex determination of Z. cucurbitae males. Our findings will help the understanding of sex determination in Z. cucurbitae and facilitate the development of genetic sexing strains in its biological control.