Duplicated Masculinizer gene and sex determination in the Mediterranean flour moth
In a study of the molecular mechanisms of sex determination in Ephestia kuehniella, we identified an ortholog of the Masculinizer gene, discovered its functional duplication, and clearly showed that the duplicated gene is essential for masculinization.
Image description: Left panel: Expression of EkMasc (A) and EkMascB (B) genes during early embryogenesis in female (pink) and male (blue) samples of Ephestia kuehniella. Significant differences between the sexes are indicated by asterisks; hpo, hours post oviposition. Right panel: the Mediterranean flour moth (Ephestia kuehniella) and its WZ/ZZ sex chromosome system.
The sex-determining cascade in the silkworm, Bombyx mori, differs greatly from those of other insects. In B. mori, female development is initiated by Fem piRNA expressed from the W chromosome during early embryogenesis. Fem piRNA silences Masculinizer (Masc) thereby blocking the male pathway resulting in female development. It is currently unknown whether this cascade is conserved across Lepidoptera. In the Mediterranean flour moth, Ephestia kuehniella, we identified an ortholog of Masc and discovered its functional duplication on the Z chromosome, which has not yet been found in any other lepidopteran species. We provided two lines of evidence that the EkMasc and/or EkMascB genes play an essential role in masculinization: (i) both genes show a peak of expression during early embryogenesis in male but not in female embryos and (ii) their simultaneous silencing by RNA interference (RNAi) results in female-specific splicing of the E. kuehniella doublesex gene (Ekdsx) in male embryos and in a female-biased sex ratio. Our results suggest a conserved role of the duplicated Masc gene in sex determination of E. kuehniella.
Visser S., Voleníková A., Nguyen P., Verhulst E. C., Marec F. (2021) A conserved role of the duplicated Masculinizer gene in sex determination of the Mediterranean flour moth, Ephestia kuehniella. PLoS Genetics 17: e1009420. DOI: 10.1371/journal.pgen.1009420