Fig. 3. Bar is the factor affected by ectopic LIM-HOM protein expression in the fourth tarsal segment. (A) Leg with Bar mutant clones marked by forked phenotype in the tarsal region. A large clone along the ventral (lower) side of the leg is outlined in black. Cells lacking Bar do not grow properly and the tarsal segments t2-t5 appear fused. Magnification of the distal part of the clone is shown in the inset, showing a remnant joint (arrow) and a forked bristle (arrowhead). (B) Leg with Bar mutant clones similar to those shown in A, except that here they also express Ap using DllGal4 (see Materials and methods). The distal tarsal segments are fused, similar to those observed in Bar clones. Inset shows a magnification of the distal part of the clone, showing a forked bristle (arrowhead) and a remnant joint (arrow). (C) Leg imaginal disc showing Bar-lacZ reporter expression in a ring of cells in the presumptive fourth and fifth tarsal region (green), and Lim1 distribution (red). (D-D'') Ectopic expression of the Lim1 gene represses Bar in a dppGal;UAS-Lim1 leg imaginal disc. (D) Lim1 protein distribution. (D') Bar protein distribution, showing an absence of Bar in the area where Lim1 is present. (D'') Merged image. (E) Leg of an apGal4/UAS-Lim1;UAS-Bar fly. Overexpression of Bar in an apGal4/UAS-Lim1 genetic background partially rescues the ap-like dominant-negative effect of ectopic Lim1 (Pueyo et al., 2000). (F) Overexpression of Bar in an apGal4;UAS-islet genetic background also partially rescues the loss of the fourth tarsal segment (compare with Fig. 2E). Magnification of the distal part is shown in the inset. A remnant joint in the dorsal part of the fused t4-t5 segment is seen (arrowhead). An apical bristle can also be distinguished (out of focus; arrowhead).