THE CAENORHABDITIS-ELEGANS GENE LIN-1 ENCODES AN ETS-DOMAIN PROTEIN AND DEFINES A BRANCH OF THE VULVAR INDUCTION PATHWAY

The Caenorhabditis elegans gene lin-1 appears to act after the Ras-Raf -MEK-MAPK signaling cascade that mediates vulval induction. We show th at lin-1 is a negative regulator of vulval cell fates and encodes an E TS-domain putative transcription factor containing potential MAPK phos phorylation sites. In lin-1 null mutants, the vulval precursor cells ( VPCs) still respond to signaling from the gonadal anchor cell, indicat ing that lin-1 defines a branch of the inductive signaling pathway. We also provide evidence that the inductive and lateral signaling pathwa ys are integrated to control the 1 degrees and 2 degrees vulval cell f ates after the point at which lin-1 acts in the inductive pathway and that VPCs can assess the relative rather than absolute levels of induc tive and lateral signaling in determining whether to express the 1 deg rees or 2 degrees vulval cell fates.