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 (a1–2) 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.