Extracellular pH has a signi cant impact on the physiology of the yeast cell, but its role in cell death has not been thoroughly investigated. We studied the effect of extracellular pH on the development of primary necrosis in Saccharomyces cerevisiae yeast under two general conditions leading to cell death. The rst is sugar induced cell death (SICD), and the second is death caused by several speci c gene deletions, which have been recently identi ed in a systematic screen. It was shown that in both cases, primary necrosis is suppressed at neutral pH. SICD was also inhibited by the protonophore dinitrophenol (DNP) and 150 mM extracellular K+, with the latter condition also bene ting survival of cell dying due to gene mutations. Thus, we show that neutral pH can suppress different types of primary necrosis. We suggest that changes to the cellular membrane potential can play a central role in yeast cell death.

Cell death in response to distinct stimuli can manifest different morphological traits. It also depends on various cell death signaling pathways, extensively characterized in higher eukaryotes but less so in microorganisms. The study of cell death in yeast, and specifically Saccharomyces cerevisiae, can potentially be productive for understanding cell death, since numerous killing stimuli have been characterized for this organism. Here, we systematized the literature on external treatments that kill yeast, and which contains at least minimal data on cell death mechanisms. Data from 707 papers from the 7000 obtained using keyword searches were used to create a reference table for filtering types of cell death according to commonly assayed parameters. This table provides a resource for orientation within the literature; however, it also highlights that the common view of similarity between non-necrotic death in yeast and apoptosis in mammals has not provided sufficient progress to create a clear classification of cell death types. Differences in experimental setups also prevent direct comparison between different stimuli. Thus, side-by-side comparisons of various cell death-inducing stimuli under comparable conditions using existing and novel markers that can differentiate between types of cell death seem like a promising direction for future studies.

Cell death plays a major role in development, pathology and aging and can be triggered by various types of acute external and internal stimuli, such as chemicals or mutations. However, little is known about chronic cell death in the context of continuing cell division. Here, we performed a genome-wide search for mutants with this type of death in dividing bakers yeast by assaying the accumulation of phloxine B, which stains dead cells. We identified 83 essential and 43 non-essential gene mutants. Surprisingly, three distinct types of spatial distribution of dead cells in colonies were observed which corresponded to gene ontology enrichments for (i) DNA replication and repair, RNA processing, chromatin organization, and nuclear transport; (ii) mitosis and cytokinesis; and (iii) vesicular transport and glycosylation/cell wall homeostasis. We further developed methods for analyzing the death of newborn cells (DON) and cell death in real time using microfluidics-based microscopy which revealed rapid stochastic necrosis during bud generation or cytokinesis without prior division arrest. This coincided with commonality of sensitivity to some plasma membrane and cell-wall perturbing agents, as well as mitigating effects of increasing external pH for most of the tested mutants. Our results suggest that rapid stochastic necrosis during cell division is a common type of cell death resulting from the dysfunction of different genes, and that this type of death seems to have a common proximal cause which might be related to the properties of the cell wall and/or plasma membrane.

Studies have reported on the ability of green fluorescent proteins to photoconvert into a red fluorescent form under various conditions, such as the presence of oxidants, hypoxia, as well as under benign conditions using irradiation with a 405 nm laser. Here, we show that in Saccharomyces cerevisiae yeast green fluorescent protein (GFP) (S65T) fused to different cellular proteins can easily photoconvert into a red form when cells are grown in media with nonfermentable carbon sources. This photoconversion occurs during standard microscopy between glass slide and coverslip but is completely prevented by imaging on pads of solid medium or in a large volume of medium on an inverted microscope. The observed effect was due to rapid hypoxia of cells with respiratory metabolism in standard conditions for upright microscopy.Photoconversion could be prevented by antioxidant treatment, suggesting that it proceeds via the effects of reactive oxidative species emerging in response to oxygen deficiency. Our results show the need for caution during upright microscopy imaging in conditions where there is active respiration and demonstrate simple approaches to prevent unwanted GFP photoconversion. They also provide easy means of performing photoconversion experiments on existing GFP-bearing cell lines, at least in the case of yeast.

Extracellular pH has a significant impact on the physiology of the yeast cell, but its role in cell death has not been thoroughly investigated. We studied the effect of extracellular pH on the development of primary necrosis in Saccharomyces cerevisiae yeast under two general conditions leading to cell death. The first is sugar induced cell death (SICD), and the second is death caused by several specific gene deletions, which have been recently identified in a systematic screen. It was shown that in both cases, primary necrosis is suppressed at neutral pH. SICD was also inhibited by the protonophore dinitrophenol (DNP) and 150 mM extracellular K+, with the latter condition also benefiting survival of cell dying due to gene mutations. Thus, we show that neutral pH can suppress different types of primary necrosis. We suggest that changes to the cellular membrane potential can play a central role in yeast cell death.