Fig. 2. The establishment of GSCs during the early pupal stage. All images represent one confocal section. Hh-lacZ is expressed in the nuclei of TFs/cap cells, whereas Hts staining highlights fusomes in germ cells and membranes of TFs/cap cells and other somatic cells. The lacZ-positive disc-like cells that are packed against each other in a line with their longitudinal axis are TFs, whereas the posterior lacZ-positive cells that do not align with TFs are cap cells. The gonads in A-D are labeled for lacZ (red) and Hts (green); the gonads in E and F are labeled for lacZ (blue), GFP (green) and Hts (red). (A,B) A hh-lacZ gonad at the larval-pupal transition stage showing only TFs. B shows two tightly packed hh-lacZ-positive TFs (brackets) without the appearance of cap cells at a higher magnification in the boxed area in A. (C) Part of a hh-lacZ female gonad at the transitional stage from larva to pupa showing finished TF cells (bracket) and newly formed cap cells. The fusome (arrow) in one of the PGCs moves close to the interface (white line) with the adjacent cap cell (arrowhead). (D) Part of a hh-lacZ female gonad also at the transitional stage showing two different PGC division patterns. In the top part, only one of the two PGC daughter cells (unbroken outline) contacts cap cells (arrowhead); in the lower part, both of the PGC daughters (broken outline) contact cap cells (arrowheads). (E,F) hh-lacZ;bam-GFP gonads showing that the two-cell clusters close to cap cells (arrowheads) are not two-cell cysts but two PGC/GSC daughters. Only one of the two GSC daughters (unbroken lines) is in juxtaposition to TFs/cap cells (arrowhead) in E, whereas both the GSC daughters (broken lines) are in close contact with TFs/cap cells (arrowheads) in F. Scale bars: 20 µm in A; 10 µm in B-F.

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