Figure 2

Duf/Kirre, Rols, F-actin, and Blow are expressed in foci during fusion of longitudinal FCs with FCMs. (A–A”) Embryo expressing rp298-lacZ in somatic and visceral FCs. (A) Mesodermal cells visualized with anti-β3-Tubulin. Arrowheads point to β-Gal-positive longitudinal FCs. (A’) Longitudinal FCs (arrowheads) are mononucleated at this stage. (A”) Embryo also expressing sns-NLSmCherry in somatic and visceral FCMs. (B–D) Embryos expressing HLH54F-lacZ. (B) Early stage 12 embryo; longitudinal FCs (arrowheads) still appear to be mononucleated. (C) Embryo in later stage 12, with multinucleated syncytia (arrowheads). (D) Embryo also expressing sns-mCherry; some syncytia appear to be sns-mCherry positive (arrowheads). (E–H”) Histochemical staining of wild-type embryos at mid or late stage 13. The embryos are shown as an overview (E, F, G, H) and at two magnifications focusing on longitudinal myogenesis (E’, F’, G’, H’ and E”, F”, G”, H”). Either heat-fixed embryos (E, F, H) or formaldehyde fixed embryos (G) were stained with anti-Kirre (E–E”), anti-Rols7 (F–F”), anti-GFP (G–G”), or anti-Blow (H–H”) antibodies. Arrows point to longitudinal FCs/growing myotubes; arrowheads indicate FCMs. At higher magnifications, local concentrations of the proteins are visible either on the side of the FC/elongation myotube, as in the case of anti-Kirre and anti-Rols7 (E’, E”; F’, F”), or in the FCM at the site of attachment for twi::act::GFP (G’, G”) and anti-Blow (H’, H”). Scale bars: 20 μm.