Fig. 1. Wild-type vulval development. During L2/L3 stages, the anchor cell (AC) induces P5.p, P6.p and P7.p VPCs to adopt 1° and 2° cell fates. The relative positions of the cell nuclei have been drawn. The terminal cell division axes are NTLL for the 2° lineage and TTTT for the 1° lineage (N, not divided; T, transverse; L, longitudinal). The Pn.pxxx cells invaginate during L4 stage to give rise to the future vulval opening. The seven differentiated cell types have been marked with colors (1° lineage vulE and vulF are red; 2° lineage vulA are white; vulB1 and vulB2 are yellow; vulC are light green; and vulD are dark green).