Genetic assessment of stationary phase for cells of the yeast Saccharomyces cerevisiae

Abstract

Starvation of cells of the yeast Saccharomyces cerevisiae caues cessation of proliteration and acquisition of characteristic physiological properties. The stationr-phase state that results represents a unique developmental state, as shown by a novel conditional phenotype (M. A. Drebot, G. C. Johston, a-d R. A. Singer, Proc. Natl. Acad. Sci. USA 84:7948-7952, 1987): mutant ells cannot proliferate at the restritve temperature when stimulated to reenter the mitotic cell cycle from staionary phase but are unaffected and continue proliferation indefinitely if transferred to the restrictive temperature during exponential growth. We have exploited this reentry mutant phenotype to demonstrate that the same stationary-phase state is generated by nitrogen, suffur, or carbon starvation and by the cdc25-1 mutation, which conditonally impairs the cyclic AMP-mediated signal transduction pathway. We also show that heat shock, a treatment that elicits physiological perturbations associated with stationary phase, does not cause cells to enter staary phase. The physiological properties associated with stationary phase therefore do not result from residene in stationary phase but from the stress conditions that bring about stationary phase.

Identification and characterization of a novel yeast gene: the YGP1 gene product is a highly glycosylated secreted protein that is synthesized in response to nutrient limitation.

“…Increased expression of YGP1 in response to the limitation of various nutrients fits with the observation that entry into stationary phase and the accompanying physiological changes occur in response to limiting nitrogen, phosphorus, or glucose (12,32,41). How each of the nutrient levels regulating the expression of YGP1 is sensed and transmitted to the cell to coordinate entry into a division cycle or into stationary phase and which specific messengers and target regions are used are not known.…”

“Sleeping Beauty”: Quiescence inSaccharomyces cerevisiae

“…Mutants lacking the GCS1 gene are conditionally (at low temperature, e.g., 15°C) unable to successfully exit from quiescence on stimulation by fresh nutrients (34,35,59,64,167). Because null alleles of GCS1 display this phenotype, the conditionality is due to a conditional requirement for Gcs1p activity.…”

“…Only one mutant, gcs1, has been confirmed to be specifically defective in exiting from the quiescent state (34,35,59,167).…”

“…68,2004 QUIESCENCE IN YEAST 189 considered a distinct developmental state comes from the gcs1⌬ mutant, which proliferates normally in the presence of food, enters quiescence when grown to stationary phase, and maintains viability in quiescence normally but is conditionally defective in exiting from quiescence and returning to active proliferation when nutrients are restored. gcs1⌬ mutants are cold sensitive only for exiting from quiescence (34,35).…”

“…The relevant gene products have been found in a variety ways: by studying the response of yeast to the immunosuppressant rapamycin; by identifying temperature-sensitive mutants that arrest in a quiescence-like state at nonpermissive temperatures even in the presence of nutrients, e.g., cdc25 (34); and by studying a subset of mutants fortuitously found to selectively lose viability when cultured to stationary phase. Here, we discuss the signaling pathways thought to regulate entry into quiescence: the TOR and protein kinase A (PKA) pathways, apparent negative regulators of the transition into quiescence; and the protein kinase C (PKC) and Snf1p pathways, apparent positive activators of the transition (Fig.…”