Fig. 3. Appendicular duf-lacZ-expressing cells are associated with tendon precursors. (A-C) duf-lacZ-expressing cells visualised in leg discs dissected from duf-lacZ; Stripe-Gal4/UAS-GFP (A) larvae, (B) prepupae and (C) pupae. (A) About 50 duf-lacZ-labelled cells (arrows) are detected in the dorsal femur close to the sr-expressing a domain. Notice that the duf-lacZ transgene is also expressed in the epithelium of the most distal leg part. (D-F) Merged Twi/duf-lacZ views confirm the presence of presumptive founder myoblasts around the a tendon domain. (B,E) At the prepupal stage (0 hours APF), the number of duf-lacZ-expressing cells around the a domain increases (arrows, compare A with B). Some of them lose twi expression. At 0 hours APF, duf-lacZ-positive cells also appear in other regions (dotted arrow in E). (F) At 5 hours APF, the sr-expressing a domain extends to form a long structure in the femur. The associated duf-lacZ cells follow the extending tendon precursor (arrowheads in C and F). Few myoblasts co-expressing duf-lacZ and Twi are visible near the g domain in the tibia (arrows in F). (G-G''') A model schematising the invagination of the tendon precursors during the leg disc eversion, showing the associated duf-lacZ-expressing cells. (H-J) Prepupal leg disc double-stained for Stripe-GFP (H) and Odd-lacZ (I; merged image is shown in J), showing co-expression of odd with sr in invaginating tendon precursors.