UCSF

Organisms often live in variable environments with the amount of essential nutrients greatly varying. Nevertheless, it is imperative that the concentration of essential nutrients be kept relatively constant within the cell or organism. Upon starvation for the essential nutrient phosphate, Saccharomyces cerevisiae responds by upregulating a large class of genes that aids it in scavenging environmental phosphate as well as utilizing its internal phosphate stores. We found that the phosphate responsive signaling pathway responds in a bistable fashion. The bistable nature of the signaling pathway depends on the proper balance between multiple positive and negative feedback loops. Bistability in the signaling pathway may allow cells to anticipate and respond to changes in environmental phosphate.