SEQUENTIAL SIGNALING DURING CAENORHABDITIS-ELEGANS VULVAR INDUCTION

DURING the induction of the Caenorhabditis elegans vulva, cell signall ing causes initially equipotent cells to express a reproducible patter n of cell fates(1,2). The position of the anchor cell determines the p attern of vulval precursor cell fates, such that the closest precursor cell (P6.p) expresses the primary cell fate, the next closest cells ( P5.p and P7.p) both express the secondary cell fate, and each of the p recursor cells located at a distance (P3.p, P4.p and P8.p) express the tertiary cell fate (Fig. 1a)(3-5). We present data indicating that th is stereotypical pattern of cell fates can be generated by sequential signals. We identified genetic mosaic animals in which P5.p and P7.p w ere defective in the anchor-cell signal-transduction pathway and obser ved that these cells adopted the secondary cell fate, indicating that anchor-cell signal transduction is not required for the expression of the secondary cell fate. These results suggest that the anchor cell in duces P6.p to express the primary cell fate, and that P6.p subsequentl y induces P5.p and P7.p to express the secondary cell fate.