Fig. 2. Embryonic origin of subsets of neurons and nonneuronal cells in the pharyngeal sense organs, as shown by HRP injection at the syncytial blastoderm stage (A D) and by FLPout (Wong et al., 2002) induced in F1 embryos of the cross MJ94 x y w hs-flp; Sp/CyO; UAS>CD2 y⁺>mCD8-GFP (E-L). (E-L) Neuronal nuclei are labeled with anti-Elav antibody (red). (A-C') HRP product is present in dendritic tips of the lso sensillum 7 (A: arrow) and of the vcso (B: arrow), as well as in dendrites, cell bodies and axons of dcso neurons (consecutive sections C,C': arrows). (D) Fishtrap bristles labeled by MJ94/UAS-lacZ (arrows) lack HRP staining, in contrast to the vcso (arrowhead). (E-I) When FLPouts are induced in the MJ94 line at 12-24 hours after egg laying (AEL), single neurons are labeled in the lso, in both sensillum 7 (composed of eight neurons) (E-G: 7) and the mononeuronal sensilla 1-6 (G: 3). By contrast, the bineuronal sensilla 8 and 9 always exhibit paired labeled neurons (H,I: arrows). Simultaneous labeling of two sensilla suggests the occurrence of two independent FLPout events (F,G). (J) FLPouts induced earlier (6-18 hours AEL) lead to simultaneous label in many neurons (e.g. three in sensillum 7). (K,L) FLPout induced at 12-24 hours AEL invariably leads to single labeled neurons in the multineuronal sensilla of the vcso (K) and dcso (L). The two large neurons in K (arrows) are outside the vcso. ftb, fishtrap bristles. Distal is to the bottom except in (A) in which distal is to the left. F shows both left and right lso. Scale bars, 20 µm (A shows scale for A-D; E shows scale for E-L).