Fig. 2. Effects of elB overexpression on tracheal gene expression. (A) The enhancer trap line l(2)01351 is expressed in a pair of cells in the dorsal trunk of each metamere (arrowhead) and in the visceral branch (arrow). The tracheal nuclei are marked by anti-Trh staining (red), and the enhancer trap by anti-ß-gal (green). (B) After elB tracheal misexpression, the enhancer trap line (green) continues to be expressed in the dorsal trunk (arrowhead), but is not observed in the residual visceral branch cells. Tracheal nuclei (red) are marked by anti-ElB. (C) kni-lacZ (green) is a target of Dpp signaling in the trachea in the dorsal branch and lateral trunks. It is also expressed weakly in the visceral branch. Red: anti-Trh. (D) After elB tracheal misexpression, kni expression (green) is retained in the reduced dorsal branches and the residual visceral branch (arrow). Red: anti-ElB. kni expression in the visceral branch that is independent of Dpp signaling was previously reported in wild-type embryos (Vincent et al., 1997; Chen et al., 1998). (E) Sal is expressed in the dorsal trunk (arrow) and oenocytes (arrowhead). Red, anti-Trh; green, anti-Sal. (F) After elB tracheal misexpression, Sal protein is retained in the oenocytes (arrowhead), but is not detected in the trachea (arrow). Red, anti-Trh; green, anti-Sal.

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