DAF-12 REGULATES DEVELOPMENTAL AGE AND THE DAUER ALTERNATIVE IN CAENORHABDITIS-ELEGANS

From egg through adult, C. elegans has six life stages including an op tion for dauer formation and diapause at larval stage L3 in adverse en vironments. Somatic cells throughout the organism make consistent choi ces and advance in unison, suggesting a mechanism of coordinate regula tion at these stage transitions. Earlier studies showed that daf-12, w hich encodes a nuclear receptor (W. Yeh, 1991, Doctoral Thesis. Univer sity of Missouri-Columbia), regulates dauer formation; epistasis exper iments placed daf-12 near the end of the dauer signaling pathway. Here we describe novel daf-12 alleles that reveal a general role in advanc ing L3 stage programs. In these mutants, somatic cells repeat L2-speci fic cellular programs of division and migration at the L3 stage; epist asis experiments place daf-12 between lin-14 and lin-28 Within the het erochronic pathway. We propose daf-12 and other heterochronic genes pr ovide cellular memories of chronological stage for selecting stage-app ropriate developmental programs. Endocrine factors could coordinate th ese stage transitions and specify developmental alternatives.