AN ANALYSIS OF THE RESPONSE TO GUT INDUCTION IN THE C-ELEGANS EMBRYO

Establishment of the gut founder cell (E) in C. elegans involves an in teraction between the P-2 and the EMS cell at the four cell stage, Her e I show that the fate of only one daughter of EMS, the E cell, is aff ected by this induction. In the absence of the P-2-EMS interaction, bo th E and its sister cell, MS, produce pharyngeal muscle cells and body wall muscle cells, much as MS normally does. By cell manipulations an d inhibitor studies, I show first that EMS loses the competence to res pond before it divides even once, but P-2 presents an inducing signal for at least three cell cycles, Second, induction on one side of the E MS cell usually blocks the other side from responding to a second P-2- derived signal. Third, microfilaments and microtubules may be required near the time of the interaction for subsequent gut differentiation. Lastly, cell manipulations in pie-1 mutant embryos, in which the P-2 c ell is transformed to an EMS-like fate and produces a gut cell lineage , revealed that gut fate is segregated to one of P-2's daughters cell- autonomously. The results contrast with previous results from similar experiments on the response to other inductions, and suggest that this induction may generate cell diversity by a different mechanism.-