Fig. 4. Olfactory precursors and amos/ato expression. (A,B) ato is expressed in the wave 1 precursors. The arrows mark the ends of this semicircular line of olfactory precursors. ato-dependent arista precursors (*) and chordotonal precursors (caret) are also marked. (C,D) ato is expressed in the wave 2 olfactory precursors (bracket). It is not expressed in the third wave, the first cells of which can be seen between the Ato rows (arrows in D). (E,F) amos is expressed in a complementary way to ato in the third wave of precursors. (E) Confocal projection of a stack of images showing Amos detection in a similar disc to D. (F) Deep confocal section from E showing nuclei of amos-expressing precursors (arrows) underlying the main amos proneural expression domain. These correspond to the non-Ato-expressing precursors (arrows in D). (G) Schematic summary of amos- and ato-dependent precursor pattern at 8 hours APF.