Identification of genes that interact with glp-1, a gene required for inductive cell interactions in Caenorhabditis elegans.

The glp-1 gene functions in two inductive cellular interactions and in development of the embryonic hypodermis of C. elegans. We have isolated six mutations as recessive suppressors of temperature-sensitive (ts) mutations of glp-1. By mapping and complementation tests, we found that these suppressors are mutations of known dumpy (dpy) genes; dpy genes are required for development of normal body shape. Based on this result, we asked whether mutations previously isolated in screens for mutants defective in body shape could also suppress glp-1(ts). From these tests, we learned that unselected mutations of eight genes required for normal C. elegans morphogenesis, including the four already identified, suppress glp-1(ts). All of these suppressors rescue all three mutant phenotypes of glp-1(ts) (defects in embryonic induction of pharyngeal tissue, in embryonic hypodermis development, and in induction of germline proliferation). However, they do not rescue putative glp-1 null mutants and therefore do not bypass the requirement for glp-1 in development. In the light of current ideas about the molecular nature of the glp-1 and suppressor gene products, we propose an interaction between the glp-1 protein and components of the extracellular matrix and speculate that this interaction may impose spatial constraints on the decision between mitosis and meiosis in the germline.