Fig. 1. Embryonic phenotype of csul^P. (A-D) The csul gene belongs to the `posterior-grandchildless' group. Immunohistochemical detection (horseradish peroxidase) of Vas protein (A,B) and cuticle preparations of first instar larvae (C,D) in wild-type (A,C) and csul^P (B,D). Anterior is to left. Pole cell formation and abdominal patterning are defective in csul^P. (E-H) csul activity is required for the localization of maternal determinants. Distribution of nos (E,F) and gcl (G,H) transcripts detected by whole-mount in situ hybridization in wild-type (E,G) and csul^P (F,H) embryos. In csul^P the accumulation of nos mRNA is reduced at the posterior pole (F), whereas gcl mRNA is evenly distributed (H). (I-L) csul^P suppresses the bicaudal phenotype induced by osk-bcd3'UTR. Immunohistochemical staining of Vas protein (I,J) and cuticle preparations of first instar larvae (K,L) in osk-bcd3'UTR (I,K) and csul^P; osk-bcd3'UTR (J,L). Although the cuticle has a normal polarity in csul^P; osk-bcd3'UTR, the head is malformed, indicating that the embryo contains a residual amount of nos activity at the anterior pole. (M-P) Distribution of Osk protein in wild-type (M,O) and csul^P (N,P) embryos. Immunofluorescent detection of Osk (red). DNA detected using Oli-Green (green). After nuclear cycle 6, the level of Osk is strongly reduced at the posterior pole in csul^P embryos (P). In older csul^P embryos (insert in P) trace amounts of Osk can be detected at the posterior pole. (Q-T) Distribution of Vas protein in wild-type (Q,S) and csul^P (R,T) embryos. Immunofluorescent detection of Vas (red); DNA (green). Similar to Osk, Vas staining is strongly reduced in the pole plasm of csul^P embryos (T) and is rarely detected at the posterior pole of syncytial embryos (insert in T). (U,V) Distribution of Tud protein in wild-type (U) and csul^P (V) embryos. Immunofluorescent detection of Tud (red); DNA (green). No localized Tud staining is observed in csul^P embryos.