Fig 1. Lineage tracing with two GAL4 drivers that are active in the hinge.

Wing discs were removed from 3^rd instar larvae without irradiation, fixed and imaged for RFP/GFP. The disc in J-L was stained with an antibody to Zfh2. All discs are shown with anterior (A) left and dorsal (D) up as in (P). Scale bar = 100 microns. (A-C) 30A-GAL4 drives UAS-RFP (real time marker) and GFP (lineage marker) (D-I) R73G07-GAL4 drives UAS-RFP (real time marker) and GFP (lineage marker). Arrows indicate the pouch area. Restricting GAL4 activity with GAL80^ts eliminated the expression of GFP in the notum (*) in (G-I). (J-L) Zfh2 antibody staining and 30A>RFP expression. Zfh2-expressing cells outside the 30A domain are indicated with arrowheads. (M) The temperature shift protocol. The embryos were collected at 18°C for 24 h and cultured at 18°C until 4–5 days after egg laying, reaching late 2^nd instar. The larvae were shifted to 29°C for 24 h to reach early 3^rd instar before irradiation with 0 or 4000 R of X-rays. The discs were dissected 48 h later (for–IR controls) or 72 h after IR (+IR samples) because IR delays development. (N) A schematic diagram to explain G-trace. Ubi = Ubi^p63E promoter. (O-P) Summary of 30A-GAL4 and R73G07-GAL4 expression (O) and the fate map with dotted lines added to indicate the pleura (P). Arrowheads point to the region that is R73G07-GAL4-expressing but outside the 30A domain. (P) is modified from [59]. The genotypes were: (A-C) 30A-GAL4, UAS-G-trace (see S1 Table for G-trace genotype)/SM5 (D-F) UAS-G-trace/+; R73G07-GAL4/+ (G-I) UAS-G-trace/+; R73G07-GAL4/tub-GAL80^ts (J-L) 30A-GAL4, UAS-G-trace /+; tub-GAL80^ts/+.