piRNAs and epigenetic conversion in Drosophila.

Area of Science:

• Epigenetics
• Small RNA biology
• Drosophila melanogaster genetics

Background:

• Transposable elements (TEs) are repressed in the Drosophila germline by Piwi-Interacting RNAs (piRNAs).
• piRNAs are produced from specific genomic loci containing TE fragments.
• The epigenetic induction of piRNA production capacity is crucial for epigenome shaping.

Purpose of the Study:

• To investigate the epigenetic induction of piRNA production capacity in Drosophila.
• To determine if piRNA production capacity can be stably inherited and transmitted.
• To explore the phenomenon of piRNA-linked paramutation in Drosophila.

Main Methods:

• Utilized two lines of D. melanogaster with a transgenic 7-copy tandem cluster (P-lacZ-white).
• Assessed piRNA production and trans-silencing capacity in different lines.
• Investigated maternal transmission of piRNAs to induce de novo piRNA production and silencing.

Main Results:

• One line (T-1) produced high levels of piRNAs and showed strong trans-silencing, while another (BX2) was deficient.
• Maternal transmission of piRNAs from T-1 conferred de novo piRNA production and silencing to BX2's locus.
• This induced capacity was stably inherited over generations and the converted locus could convert others, demonstrating paramutation.

Conclusions:

• Established the first stable paramutation in animals, termed piRNA-linked paramutation.
• Demonstrated a stable epigenetic conversion process for piRNA production locus emergence.
• Provides a model system to study epigenetically induced piRNA production and its role in epigenome shaping.