View Program - 63rd Annual Drosophila Research Conference

Maternally deposited piRNAs act as epigenetic vectors to pass on transgenerational memory of selfish genetic elements to the offspring. This model posits that the maternal input instructs the zygotic genome to mount a piRNA program in the next generation that reflects the maternal response to genomic parasites. However, males implement a piRNA program distinct from the maternal instruction and their female siblings. Here, we disentangled the contribution of three factors – sex chromosome content, gonadal sex, and maternal input – towards a sex-specific piRNA program. While maternally deposited piRNAs can identify homologous sequences as piRNA-producing loci in the zygote, we found de novo piRNA production that does not rely on maternal input but instead depends on the chromosome content and gonadal sex. In fact, Y chromosome is both necessary and sufficient to recapitulate some key aspects of male piRNA program. Meanwhile, sexual identity exerts a major influence on divergent piRNA production from identical genomic sequences between sexes. Our work showed that it is the collective action of chromosome content, gonadal sex and maternal input that sculpts the observed sexual dimorphism in piRNA program, highlighting a previously unknown input from sexual identity into piRNA biogenesis.

Sculpture of a sex-specific piRNA program