Figure 5. Expression of bnl-LexA in tracheoblast niche of the leg imaginal discs. A-B′.
bnl-LexA expression pattern in early (A-A′) and mid (B-B′) developmental stages in the L3 larval leg discs (3rd leg). A′, B′; 40X images of A and B, respectively. C, C; Anti-E-Cad staining marked cell junctions of the disc epithelial bnl source (red; C) and the apical (green) lumen (C) of the tracheal tube lined by the tracheoblast cells. D, wing- and 3rd leg imaginal discs with associated neo-tracheal tubes containing tracheal progenitors (btl-Gal4 X UAS-CD8:GFP; arrow); ASP originates from the TR2 transverse connective (TC) in wing disc and leg disc tracheoblasts migrate from the ganglionic branch. Cell nuclei marked by Histone-RFP (His2Av-mRFP1) transgene. Chitinous lumen of the tracheal tubes (blue) were imaged with autofluorescence in 405 nm channel. E, F; cell proliferation detected by EdU incorporation (red) in ex vivo cultured wing and leg discs and in the associated tracheal progenitor cells in the leg- (E, see supplementary movie 11) and in the wing- discs (F). G-G′; Btl-DN expression in trachea suppressed tracheal migration into the leg disc but did not affect disc bnl expression (btl-Gal4, UAS-CD8:GFP/+; bnl-LexA,lexO-CherryCAAX/UAS-btlDN); G′, 40X image of G. H-H′; Activated-Btl expression (btl-Gal4, UAS-CD8:GFP/+; bnl-LexA,lexO-CherryCAAX/UAS-ABtl) in trachea resulted in abnormal growth of tracheoblast cells at the base of the leg disc but these cells did not follow the bnl -expressing cellular track into the leg discs; H′, 40X image of H. I-J, Cytonemes (arrows) at the tip of the growing tracheal branch in leg disc in live (I) and in fixed condition (J). Genotypes: A-C, J; btl-Gal4,UAS-CD8:GFP/+; bnl-LexA,lexO-CherryCAAX/+. E,F,I; btl-Gal4, UAS-CD8:GFP. Scale bars, 30 μm; A,B,D,G,H, 60 μm.