The transcriptional
rom-1::nls::gfp reporter was widely expressed in somatic cells throughout development. Surprisingly, no
rom-1::nls::gfp expression was in the gonadal AC before the L4 stage, while consistent expression was observed in the Pn.p cells and the Pn.a-derived neurons from the L1 stage on. In early L2 zhIs5 larvae, the six VPCs expressed
rom-1::nls::gfp at equal levels. The Pn.p cells that are not part of the vulval equivalence group and had fused to
hyp7 at the end of the L1 stage showed relatively higher
rom-1::nls::gfp expression than the VPCs (for example, P1.p, P2.p, and P9.p). Toward the end of the L2 stage,
rom-1::nls::gfp expression decreased in distal VPCs adopting the 3N0 uninduced fate and persisted in the proximal VPCs adopting induced vulval fates. In 60% of zhIs5 animals, there is an up-regulation of
rom-1::nls::gfp in P6.p, and in 35% and 45% of the cases,
rom-1::nls::gfp expression was higher in P5.p and P7.p, respectively (n = 20). After vulval induction,
rom-1::nls::gfp was down-regulated in the primary and secondary descendants of P5.p, P6.p and P7.p, while the tertiary descendants of P3.p, P4.p, and P8.p again expressed high levels of
rom-1::nls::gfp after they had fused with
hyp7. Expression of
rom-1::nls::gfp was observed in the AC and other cells of the somatic gonad only beginning in the L4 stage, before the AC fused with the uterine seam cell and persisting after fusion.