Fig. 1. The downregulation of gcm precedes the induction of lz in the anterior-most row of prohemocytes. (A,B) gcm (red) and srp (green) transcription in stage 5 (A) or stage 6 (B) embryos. (C) gcm transcript (red) and SRP protein (green) expression in stage 6 embryo. (D,E) lz-lacZ embryo processed to reveal gcm transcript (red) and ß-gal protein (green) at stage 7 (D) and at stage 10 (E). (F-J) lacZ expression in lz-lacZ (F) or lz-gal4/uas-gal4; uas-gal4/+; uas-gal4/uas-lacZ (G-J) embryos at stage 7 (F,G, ventral views), stage 11 (H, side views) or stage 14 (I, side views). (J) High magnification views of lacZ-expressing cells localised in the crystal cell cluster (left panel) or far from the cluster (right panels) in a stage 14 lz-gal4/uas-gal4; uas-gal4/+; uas-gal4/uas-lacZ embryo. (K-M) Side views of gcm-lacZ embryos processed to reveal DoxA3 mRNA (red) and ß-gal protein (green) at stage 11 (K), 14 (L) or 15 (M). (N,L) Side views of DoxA3 mRNA (red) and ß-gal protein (green) in srp-Gal4;uas-lacZ (N) or lz-lacZ (O) embryos at stage 15. Contrary to lz-lacZ or srp-lacZ, gcm-lacZ expression is progressively lost in the crystal cells during embryogenesis: 26 out of the 28 DoxA3⁺ cells are gcm-lacZ⁺ at stage 11 (K), against 9 out of 27 at stage 14 (L) and 0 out of 27 at stage 15 (M). lz-lacZ codes for a cytoplasmic ß-gal whereas gcm-lacZ and uas-lacZ code for a nuclear ß-gal.