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Fig. 1. Branching morphogenesis of the Drosophila tracheal system
during embryonic development. Stills from time-lapse movies showing
Drosophila embryos expressing either (A)
His2AvD::mRFP ubiquitously or (B-D) GFP::Actin in the
tracheal system (see Movie 1 in the supplementary material). (A) Stage 11 of
embryonic development. Tracheal cells invaginate (arrowheads) and form
tracheal sacs during the initial phase of germ band retraction. (B) Stage 12
of embryonic development. Tracheal sacs extend branches in stereotyped
directions (asterisks). (C) Stage 14 of embryonic development. Tracheal
branches elongate. (D) Stage 15 of embryonic development. Some branches are
fusing to form an interconnected network of tracheal tubes (arrowheads). DBs,
dorsal branches; DT, dorsal trunk; TCs, transverse connectives. Anterior is to
the left and dorsal to the top. Scale bars: 100 µm.