Fig. 4: The RNA helicase Pit is enriched in the PCH void in −rDNA embryos.
a, Protein subdomains in Pit (top). Localization of RFP–Fib and Pit–GFP in a late embryo (bottom left), RFP–HP1a and Pit–GFP in a late embryo (bottom middle), and Scarlet-I–HP1a and Pit–mYFP transfected in S2R+ Drosophila cells (bottom right). Magnified views of the delineated regions in the main images are provided. b, Maximum intensity projections of cycle 14, cycle 17 and amnioserosa nuclei of +rDNA and −rDNA embryos expressing RFP–HP1a and Pit–GFP. Yellow arrows in −rDNA embryos in cycle 14 show the mixing of Pit and HP1a, whereas those in −rDNA in cycle 17 and amnioserosa show the formation of the Pit neocondensate in the PCH void. The schematic (left) summarizes the dynamics of HP1a, Fib and Pit during embryonic development in +rDNA and −rDNA nuclei. c, Time-lapse still images (single slices) of a −rDNA amnioserosa nucleus expressing RFP–HP1a and Pit–GFP; t = 0 min marks the start of a 90-min time window that captures the emergence of the Pit neocondensate within HP1a in amnioserosa nuclei. d, Mean intensity normalized to its value at t = 0 min. e,f, Circularity (e) and area of projections (f) of Pit–GFP neocondensates in amnioserosa nuclei of −rDNA embryos over time. At each time point, Pit–GFP segments correspond to one Pit neocondensate per amnioserosa nucleus, averaging 14 measured nuclei per embryo. d–f, Plotted values represent the average of mean measurements from n = 3 embryos over time. The error bars show the s.e.m.
