Which signaling pathway is responsible for vulva induction in C. elegans?
Vulval induction relies on conserved RTK/Ras/MAPK cascade downstream of anchor cell EGF signal. Anchor cell in somatic gonad secretes LIN-3 EGF-like ligand, which binds LET-23 EGFR homolog on vulval precursors P5.p-P7.p, localized basolaterally by LIN-2, LIN-7, LIN-10 scaffolding complex. Activated LET-23 recruits SEM-5 Grb2 adaptor, LET-60 Ras, LIN-45 Raf, MEK-2 kinase and MPK-1 ERK, phosphorylating transcription factors LIN-1 ETS and LIN-31 forkhead. Highest LIN-3 concentration near P6.p specifies primary vulval fate, while lateral LIN-12 Notch ligands from P6.p drive secondary fates in neighbors, ensuring precise three-cell patterning and morphogenesis.
Ref: Gilbert, Developmental Biology, 12th ed., Chapter 8: Vulval induction - RTK/Ras/MAPK pathway and LIN-3 signaling.