Figure 4.

Many third instar larval CNS neurons never express para. G-Trace signaling was used to determine whether CNS neurons of third instar larvae had historically expressed para. A, The G-Trace method labels present expression of para-T2A-GAL4 with UAS-RedStinger.nls and historical para-T2A-GAL4 expression with UAS-Flippase and Ubip63 >FRT-STOP-FRT Stinger.nls. B, Comparison of Stinger and RedStinger in the VNC shows almost a complete overlap indicating that, once cells activate para expression, it remains on. C, In the central brain, most of the historical and current staining overlaps; however, a small number of Stinger-positive, RedStinger-negative cells can be observed.