NOVEL FACTOR HIGHLY CONSERVED AMONG EUKARYOTES CONTROLS SEXUAL DEVELOPMENT IN FISSION YEAST

In the fission yeast Schizosaccharomyces pombe, the onset of sexual de velopment is controlled mainly by two external signals, nutrient starv ation and mating pheromone availability. We have isolated a novel gene named rcd1(+) as a key factor required for nitrogen starvation-induce d sexual development. rcd1(+) encodes a 283-amino-acid protein with no particular motifs. However, genes highly homologous to rcd1(+) (encod ing amino acids,vith >70% identity) are present at least in budding ye asts, plants, nematodes, and humans. Cells with rcd1(+) deleted are st erile if sexual development is induced by nitrogen starvation but fert ile if it is induced by glucose starvation. This results largely from a defect in nitrogen starvation-invoked induction of stel1(+), a key t ranscriptional factor gene required for the onset of sexual developmen t. The striking conservation of the gene throughout eukaryotes may sug gest the presence of an evolutionarily conserved differentiation contr olling system.