Fig. 6. Actin isoform incorporation into sarcomeric assemblies in adult indirect flight muscles. (A) Using the mef2-Gal4 driver all six actins were expressed in the adult indirect flight muscles. A single muscle myofibril of an adult indirect flight muscle is shown for each actin. GFP is shown in the left column and in green in the colour images, and phalloidin is shown in the middle column and in red in the colour images. Note that, apart from the Z-lines, GFPactins appear to be more strongly incorporated into a `core' structure of the indirect flight muscle. (B) The `core' incorporation pattern of GFPactins is preserved when actins are expressed with other Gal4-drivers that have different levels and timing of expression; shown are GFPactin5C and GFPactin42A using CY2-Gal4, and GFPactin88F using 24B-Gal4 (colour panels show GFP in green and phalloidin in red and the black and white panels show GFP alone). (C) Schematic showing the continuous assembly of indirect flight muscle myofibrils during pupal stages (Reedy and Beall, 1993a). A section through thin filaments of a sarcomere is shown and a cross section of an individual sarcomere between two Z-lines. The darker the colour, the earlier the corresponding thin filaments have been assembled. (D) Disorganisation of the indirect flight muscles caused by GFPactin overexpression. Overview of a field of indirect flight muscle fibres expressing actin5C. Note that some fibres appear to split and fuse irregularly (arrows), a feature not observed in wild-type fibres.