Masculinizer-induced dosage compensation is achieved by transcriptional downregulation of both copies of Z-linked genes in the silkworm, Bombyx mori

Dosage compensation balances the expression of sex-chromosome-linked genes with autosome-linked genes in the heterogametic sex. The silkworm (Bombyx mori), a lepidopteran model insect, uses the female heterogametic WZ sex determination system. In B. mori, a Z-linked gene, Masculinizer (Masc), is the primary determinant of maleness and dosage compensation. However, it remains unknown whether one of the two Z chromosomes is inactivated or both Z chromosomes are suppressed in B. mori males. Hence, we performed transcriptome analysis using hybrids between two B. mori strains and analyzed the allele-specific expression (ASE) to solve the problem. The ASE analysis revealed that the genes located on the maternal and paternal Z chromosomes are transcriptionally upregulated in Masc knocked down males. Also, our results revealed that two Z chromosomes are transcriptionally downregulated in B. mori males as observed in Caenorhabditis elegans.