Increasing population growth by asy mmetric segregation of a limiting resour ce during cell division

When stressed by metal depletion, budding yeast adopt an asymmetric division pattern whereby vacuoles are maintained within dividing mother cells while the vacuoles-deprived daughter cells arrest division. This linear growth mode represents a bet-hedging strategy beneficial at the population level.
Budding yeast restricts division to a subpopulation of mother cells when metal is depleted. This population splitting into dividing mothers and arrested daughters implements a bet-hedging strategy beneficial for population long-term survival. Proliferation is limited by the availability of vacuoles, which are asymmetrically segregated to mother cells in a WHI5-dependent manner. Asymmetric resource distribution increases population growth under limiting conditions, defining a novel stress-response strategy.
We report that when budding yeast are transferred to low-metal environment, they adopt a proliferation pattern in which division is restricted to the subpopulation of mother cells which were born in rich conditions, before the shift. Mother cells continue to divide multiple times following the shift, generating at each division a single daughter cell, which arrests in G1. The transition to a mother-restricted proliferation pattern is characterized by asymmetric segregation of the vacuole to the mother cell and requires the transcription repressor Whi5. Notably, while deletion of WHI5 alleviates daughter cell division arrest in low-zinc conditions, it results in a lower final population size, as cell division rate becomes progressively slower. Our data suggest a new stress-response strategy, in which the dilution of a limiting cellular resource is prevented by maintaining it within a subset of dividing cells, thereby increasing population growth.