Figure 9.

A PIWI-family is involved in a trans-nuclear cross-talk. Immunofluorescence of Piwi/mdp1 (green) and DNA counterstaining (red). The cellular shape was visualized using an α-tubulin-antibody (grey). Confocal image stack projections. (A) Early during conjugation Piwi/mdp1 accumulates in a subset of micronuclei (m), and some scattered foci-like signals are observed in the fragmented parental macronuclei (p). During conjugation (B), and early after separation of conjugating cells (C), Piwi/mdp1 is highly enriched in the fragmented parental macronuclei (p) but is no longer detected in micronuclei (m). (D-H) At subsequent developmental stages Piwi/mdp1 signals totally vanish from the fragmented parental macronuclei (p). (D) Instead Piwi/mdp1 relocalizes in the macronuclear anlage and exhibits maximum signal intensity at an early stage (a_1–2) during the first DNA amplification stage. (E, F) As polytenization proceeds (a₂ in (E) and a₃ in (F)), Piwi/mdp1 signals becomes organized as discrete foci. (G) Scattered Piwi/mdp1 signals are still detected at stages (e) during DNA elimination. (H) At stages (r) during the second rounds of DNA amplification no more Piwi/mdp1 signals are observed.