Aging and differentiation in yeast populations: elders with different properties and functions

Abstract

Over the past decade, it has become evident that similarly to cells forming metazoan tissues, yeast cells have the ability to differentiate and form specialized cell types. Examples of yeast cellular differentiation have been identified both in yeast liquid cultures and within multicellular structures occupying solid surfaces. Most current knowledge on different cell types comes from studies of the spatiotemporal internal architecture of colonies developing on various media. With a few exceptions, yeast cell differentiation often concerns nongrowing, stationary-phase cells and leads to the formation of cell subpopulations differing in stress resistance, cell metabolism, respiration, ROS production, and others. These differences can affect longevity of particular subpopulations. In contrast to liquid cultures, where various cell types are dispersed within stationary-phase populations, cellular differentiation depends on the specific position of particular cells within multicellular colonies. Differentiated colonies, thus, resemble primitive multicellular organisms, in which the gradients of certain compounds and the position of cells within the structure affect cellular differentiation. In this review, we summarize and compare the properties of diverse types of differentiated chronologically aging yeast cells that have been identified in colonies growing on different media, as well as of those found in liquid cultures.

Stratification of yeast cells during chronological aging by size points to the role of trehalose in cell vitality

“…Over the past years, evidence has been accumulating in support of the idea that unicellular yeast are able to differentiate into specialized cell types and could therefore serve as a primitive model of developing metazoan tissues (for review Palková et al 2014). In the present study, we approached the differentiation of chronologically aged yeast liquid cultures from the perspective of cell size, as we observed that the size distribution profiles of cultures changed during cultivation.…”

“…More recently, a growing body of evidence shows that, on reaching stationary phase, yeast cells differentiate into several subpopulations with distinct physiology, whether grown in liquid culture or as colonies on solid medium (Allen et al 2006; Palková et al 2014). This finding has opened up a new field of study of unicellular yeast differentiation, which may help us to understand the development of higher-eukaryotic tissues.…”

Similar environments but diverse fates: Responses of budding yeast to nutrient deprivation

“…Sporulation occurs under the specific condition of active respiration (NFCs being much higher than FCs), high pH, and depleted nitrogen and/or other nutrients (reviewed in 156157). Quiescence, like sporulation, is triggered by the absence of at least one essential growth nutrient and alkaline pH, but (unlike sporulation) quiescence does not have a requirement for respiration (reviewed in 10158. Finally, pseudohyphal differentiation occurs at intermediate-to-low nitrogen concentrations (reviewed in 135), can also be induced by other cues such as fusel alcohols, and also responds to other cues in some strain backgrounds (reviewed in 159).…”

“…Although quiescence can be induced in a range of environments, extracellular environment strongly influences the properties of Q cells. For example, metabolic and other biological properties of Q cells vary depending on which nutrient is limiting (reviewed in 10164). These different properties suggest the existence of multiple types of Q cells depending on the presence or absence of particular environmental cues.…”

“…1). In particular, as nutrients become depleted, these cells differentiate in at least three distinct ways: 1) they can sporulate to form haploid spores (reviewed in 56), 2) they can switch into "pseudohyphal growth" (phg) to grow as elongated chains of cells (reviewed in 789), or 3) they can enter a stable non-proliferative state known as "quiescence" or "stationary phase" where they age and eventually undergo programmed cell death (reviewed in 101112). …”