Fig. 2.

The GPC areas release Wg to induce wg in the s-IPC. a, b Schematic in a highlights the region of interest shown in subsequent panels. Unlike in controls (a), Wg immunolabeling (green) was absent in the s-IPC (dashed line, double arrowhead) in many wg{KO;NRT-wg} flies (b). The GPC areas (arrowhead) were not affected. c, d In 2nd instar larvae (2L), Wg protein (c, green) and wg{KO;Gal4} UAS-cd8GFP (d, green) were detected in GPC areas (arrowhead), but not in the adjacent IPC (dashed line). e, f s-IPC-specific wg{KO;Gal4} UAS-cd8GFP expression (green, double arrowheads) in mid 3rd instar larvae (e) was absent in wg{KO;NRT-wg} flies (f). Arrowheads indicate expression in GPC area. g, h In controls, wg{KO;Gal4} UAS-FLP mediated wg{KO;FRT wg⁺ FRT NRT-wg} allele switching and simultaneous UAS-NRT-wg overexpression were induced at the mid 3rd instar larval stage (g, wg⁺ background). Allele switching at the 1st instar larval stage (h, NRT-wg background) did not rescue s-IPC-specific Wg loss (green). i, j Unlike in controls (i), R46E01-Gal4 UAS-FLP-mediated GPC areas-specific wg{KO;FRT NRT-wg FRT wg⁺} allele switching (j) rescued s-IPC-specific NRT-Wg loss (green). Filled and open triangles in transgene schematics represent FRT and loxP sites, respectively (g–j). k, l The Wg target gene reporter lines fz3^G00357-GFP (k, green) and notum^WRE-lacZ (l, green) show expression in the GPC areas, the s-IPC, and in migratory progenitors (arrow) originating from the adjacent p-IPC. m, n Unlike in controls (m), fas3^NP1233-Gal4-mediated IPC-specific fz and fz2 knockdown (n) caused loss of Wg (green) in the s-IPC. o Summary of wg function in the GPC areas. For genotypes and sample numbers, see Supplementary Table 1. Scale bars, 50 μm