DIFFERENT LEVELS OF THE C-ELEGANS GROWTH-FACTOR LIN-3 PROMOTE DISTINCT VULVAR PRECURSOR FATES

An invariant spatial pattern of three cell fates (3 degrees-3 degrees 2 degrees-1 degrees-2 degrees-3 degrees) is generated from a field of multipotent precursor cells during C. elegans vulval development. We d emonstrate that the epidermal growth factor-like domain of the LIN-3 p rotein can induce either of two distinct vulval cell fates: a high dos e of LIN-3 induces a 1 degrees fate; a lower dose of LIN-3 induces a 2 degrees fate. A high dose of LIN-3 can also induce adjacent vulval pr ecursor cells to assume 1 degrees fates; thus, high levels of LIN-3 ca n override the lateral signaling that normally inhibits formation of a djacent 1 degrees fates. We propose that the invariant pattern of vulv al cell fates is generated by a graded distribution of LIN-3 that prom otes different vulval fates according to local concentration and by a lateral signal that reinforces this initial bias.