Specification of gut cell fate differs significantly between the nematodes Acrobeloides nanus and caenorhabditis...

The classic view of a strictly cell-autonomous development in nematode embryos has been overturned in recent years with the demonstration of various inductive interactions during early development of Caenorhabditis elegans. To examine how conserved the pattern of embryonic cell specification is among nematodes, we have begun to study the pattern in other species after selective elimination of certain early blastomeres. Here we report considerable differences in specification of the gut lineage between C. elegans and Acrobeloides nanus, another free-living soil nematode belonging to the same order. In C. elegans none of the early blastomeres is by itself able to establish a gut lineage for which an inductive interaction between the somatic EMS cell and its germline sister P2 is required. In contrast, in A. nanus all blastomeres of the 3-cell stage carry the potential to generate gut cells. Our data suggest that repressive interactions take place among blastomeres to ensure that under normal conditions only one of them executes the gut fate. Thus, in related species of nematodes with a very conserved morphology, the assignment of cell fate during early embryogenesis appears to involve quite different strategies.