Fig. 1. Appendicular myoblasts in second and third instar larvae. (A,B) Leg discs from a second larval instar. (A) All the Twi-positive myoblasts co-express the 1151-GFP marker. (B) All second instar appendicular myoblasts, except those located in the stalk (arrowhead), express a mitosis marker (red), indicating that they are proliferating. (C,D) Leg discs from late third instar larvae. (C) Several hundreds of appendicular myoblasts co-expressing 1151-GFP and Twi are detected. (D) In the third larval instar, the majority of leg disc myoblasts do not display mitotic activity. Proliferating epithelial cells are indicated by arrows. (E,F) A prepupal leg disc stained for 1151-GFP and Twi, showing a subset of non-mesodermal (Twi-negative) 1151-GFP cells. These cells are seen within the outlined area and along the double-headed arrow. (G,H) Non-mesodermal 1151-GFP cells co-express Sr, indicating that they correspond to tendon precursors. Presumptive tarsal (double-headed arrow) and femur tendon precursors (arrow) are indicated. Asterisks in G point to the background staining resulting from the weak signal to background ratio seen when using the available anti-Sr antibody.