Behavior of yeast under diverse starvation conditions
Naomi Ziv and David Gresham
Center for Genomics and Systems Biology, New York University
Motivation
Experimental method
Yeast spend the majority of their life in a quiescent state yet little is known about the molecular processes that are
important for entry, maintenance and exit from a non-proliferative state. One established protocol for studying this process
in the laboratory entails starvation of yeast by growing them in rich media to saturation and then placing them in water for
prolonged periods. Under these conditions, strains maintain high viability (Granot & Snyder, 1991).
We studied yeast grown to saturation both in YPD and in phosphate limiting media and subsequently transferred to water in
the presence or absence of specific nutrients (glucose, phosphate and amino acid supplements). We find that the addition of
glucose results in a decline in viability of both YPD and phosphate-starved cells. Our findings support the notion that glucose
is used as a signal for the presence of external nutrients, promoting exit from stationary phase even following conditions of
phosphate limitation.
Starvation in Phosphate-limiting media
Starvation in YPD
A previous study suggested that following
starvation in YPD the addition of glucose
induces re-entry into the cell cycle causing
a rapid decline in viability due to the lack of
sufficient nutrients to support growth
(Granot & Snyder, 1991). Consistent with
this expectation, we found that
supplementing for the strain auxotrophies
(uracil, leucine, lysine and histidine) partially
suppresses the rapid decline in viability.
Conclusion: Yeast do not sense the internal
state of key bimolecular precursors when
committing to cell cycle re-entry.
BY4742: Mat α, his3Δ1,
leu2Δ0, lys2Δ0, ura3Δ0
Starvation in YPD
T=24h
T=48h
T=72h
Viability remained high when phosphate starved cells were transferred to water. Surprisingly,
viability decreased in the presence of glucose and not in the presence of phosphate. This
decline does not appear to be due to the strain auxotrophies as the same pattern was
observed with the prototrophic strain FY5.
Conclusion: Environmental signals for exit and subsequent re-entry into the cell cycle need not
be complementary. This discordance may reflect metabolic activity during quiescence.
T=144h
Water
Water +
glucose
Water +
glucose +
auxotrophic
supplements
Future directions
We plan to use quantitative barcode sequencing to identify mutants and cellular
processes that underlie exit and re-entry into the cell cycle upon glucose re-addition
and other diverse conditions.
Reference:
Granot D, Snyder M, PNAS, 1991
FY5: Mat α
Starvation in Phosphate
limiting media
BY4742
Starvation in Phosphate
limiting media
T=24h
Water +
Glucose
Water +
Phosphate
Water +
Glucose
Water +
Phosphate
T=48h
T=72h
T=144h