Fig. 1.

Fusion events affecting VPC competence and patterning. Pn.p cells are born during the mid-L1 stage; the anterior Pn.p cells (P1.p and P2.p) and the posterior Pn.p cells (P9.p, P10.p, and P11.p) fuse to hyp7 by the late L1 stage. In 50% of hermaphrodites, P3.p fuses to hyp7 during the L2 stage; in the other 50%, P3.p, along with P4.p and P8.p, divide after vulval induction in the L3 stage. Their daughters (“Pn.px”) fuse to hyp7 soon after birth, whereas P5.px, P6.px, and P7.px remain unfused and undergo further rounds of cell division, generating vulval cells.