Fig. 4. Expression of egl-18/elt-6::GFP. (A-C) Expression of pKK63 containing an 800 bp enhancer and a basal promoter. (A) L2 larva, in which all VPCs (P3.p-P8.p) show approximately equal levels of GFP expression (arrows). All six VC neurons show GFP expression, although not all are visible in this focal plane. Arrowhead indicate a VC neuron. (B) L3 larva shortly before VPC divisions, showing stronger GFP expression in P5.p-P7.p cells than in P4.p and P8.p. (C) L3 larva after the first VPC cell divisions. Daughters of P6.p show higher GFP expression than daughters of P5.p and P7.p. GFP expression is not detectable in P4.px and P8.px cells. (D) Early-L3 larva showing expression of an elt-6 transcriptional fusion pKK41 in P5.p-P7.p cells. pKK41 contains 8 kb of genomic sequence upstream of the elt-6 ATG, including the 800 bp enhancer in pKK63 (Koh and Rothman, 2001).