Fig. 4. Wingless acts sequentially to specify Slouch clusters I and II. (A-F) Ventral views of late Stage 11 embryos stained with Slouch; anterior is left. cI (black arrowhead) and cII (white arrowhead) are indicated in both panel and insets. Black arrows denote the midline in panels and Slouch-expressing CNS cells in insets. (A) Loss of hh function causes a loss of cII in most hemisegments but does not effect cI expression as strongly. (B) hh embryos in which wg is now expressed in the mesoderm reveals that Hh does not have a specific input to cII. cII and cI are specified normally. (C) Embryos carrying the hypomorphic allele wg^IL114 raised at 18°C for 15 hours show Slouch expression in both cI and cII. (D) Embryos carrying the hypomorphic allele wg^IL114 raised at 25°C for 8 hours show complete loss of mesodermal Slouch expression, although Slouch continues to be expressed in the CNS as in wg^CX4 embryos. (E) Embryos carrying the hypomorphic allele wg^IL114 raised at 18°C for 13 hours and shifted to 25°C for 2 hours show partial loss of Slouch expression in cII. (F) Embryos carrying the hypomorphic allele wg^IL114 raised at 18°C for 12 hours and 25°C for 3 hours show complete loss of Slouch cII and no loss of cI. (G) Quantification of Slouch cluster loss when Wg levels are manipulated by hh alleles and temperature shifts. Graphs show percentage of hemisegments in which cI (blue) or cII (red) are present. ^**, conditions in which cI and cII appeared in the same hemisegment; n, number of hemisegments counted.