Figure 6
Time of birth and distribution of Br-Z4+ neurons in the thoracic lineages. (A) Schematic, showing the timing of heat-shocks (hs; arrows) to induce MARCM clones during larval neurogenesis and the time of analysis of the clones at pupariation [B, D, F] or just before adult emergence [C, E]. The cartoons show the predicted relationship of clone boundaries (green) to Br-Z4 expression (magenta), if the Br-Z4+ neurons were born during a discrete phase of larval life. P0, puparium formation. (B) Z-projections of lineage 14 neuroblast clones that were examined at pupariation but induced by heat shocks at 24 h or 76 h AEL. Left: anatomy of the whole clone. Right: sections from the basal (b) and middle (m) portions of the clone. The basal cells in early induced clones are Br-Z4 negative with the Br-Z4+ cells clustered in the middle layers. In the 76 h-induced clone, the oldest (basal) cells included only a few Br-Z4+ neurons (arrows) but positive neurons were outside the clone. (C) Examples of two-cell GMC clones from the adult CNS; examples from heat-shocks at 77 h AEL show both sibs expressing Br-Z4 or one sib with weak expression (arrow) and the other negative. Both sibs are negative after the late heat-shock induction. (D) Summary of neuroblast MARCM clones that were examined around the time of pupariation. Only clones induced at 99 h AEL were completely devoid of Br-Z4+ neurons. (E) Summary of GMC clones that were examined just prior to adult emergence. Br-Z4+ neurons were most commonly seen in clones induced at 77 h AEL. For (C, D), the numbers above each bar are the numbers of clones examined. (F) Counts of the number of Br-Z4+ neurons in neuroblast MARCM clones that were induced at 24 h (black dots) and 76 h (red dots) AEL. The neuroblast of origin was identified by the morphology of the axon bundles that exited the clone. Interneuron-generating lineages were grouped by whether they produced one or two classes of interneurons. Some neuroblasts (NBs 1 and 19) were in both categories because of segment-specific loss of one class of interneurons. The black and red bars give the averages for the two groups. MN, motor neuron lineages.