Fig. 2. Spatial distribution of appendicular myoblasts and tendon precursors during larval and early pupal stages. (A-D) Tendon precursor position revealed by Stripe-Gal4/UAS-GFP with respect to the Wg-positive anteroventral domain (A,B) and the Dl-labelled proximodistal axis (C,D). (A,C) In the third instar leg disc, five GFP patches are observed. They are designated a in dorsal, b and c in ventral, e in posteroventral, and d in the distal part of the leg epithelium. (B,D) At 0 hours APF, tendon precursors invaginate and become extended. The proximodistal positions of tendon precursors are as follows: the a and b patches lie within the femur, c lies within the tibia and d crosses the tarsus, tibia and femur. At the onset of eversion (D) two supplementary tendon precursors, e in the proximal region (coxa, trochanter) and g in the dorsal tibia, are detected. (E-H) Merged images showing myoblast (blue) and tendon precursor (green) organisation in relation to the dorsoventral and proximodistal axes. Note that at 0 hours APF (F,H), myoblasts are excluded from the most distal part of the disc (double-headed arrows). Disc orientation is noted by: A, anterior; P, posterior; V, ventral; D, dorsal; Pr, proximal; and Di, distal.