Relationship between the replicative age and cell volume in Saccharomyces cerevisiae.

Abstract

Reaching the limit of cell divisions, a phenomenon referred to as replicative aging, of the yeast Saccharomyces cerevisiae involves a progressive increase in the cell volume. However, the exact relationship between the number of cell divisions accomplished (replicative age), the potential for further divisions and yeast cell volume has not been investigated thoroughly. In this study an increase of the yeast cell volume was achieved by treatment with pheromone alpha for up to 18 h. Plotting the number of cell divisions (replicative life span) of the pheromone-treated cells as a function of the cell volume attained during the treatment showed an inverse linear relationship. An analogous inverse relationship between the initial cell volume and replicative life span was found for the progeny of the pheromone-treated yeast. This phenomenon indicates that attaining an excessive volume may be a factor contributing to the limitation of cellular divisions of yeast cells.

Hypertrophy hypothesis as an alternative explanation of the phenomenon of replicative aging of yeast

“…Scheme drawn on the basis of cell volumes measured experimentally (Zadrag-Tecza et al, 2009). increase in cell size does not necessarily lead to a shortening in life span'. However, the results of our studies brought quite different results, fully supporting the hypertrophy hypothesis (Zadrag et al, 2005(Zadrag et al, , 2006Zadrag-Tecza et al, 2009). Moreover, experimental elevation of cell volume by nocodazole treatment or by growing the cdc28 mutant at restrictive temperature (Yang et al, 2011) also shortened rls.…”

“…According to the rules of methodology of sciences, the natural phenomenon, which always accompanies the studied one, is most probably its causative factor if other accompanying phenomena can be eliminated without elimination of the phenomenon studied (Ducheyne, 2008). We have postulated Zadrag et al, 2006) that simply reaching excessive volume by yeast cells at the end of their reproductive period is responsible for their inability to undergo further reproduction. The only a priori assumption, on which all hypotheses are based, is that the level of any senescence factor cannot increase infinitely.…”

“…(2) The cells of strains of the same genetic background stop budding after reaching identical volume, irrespective of the number of completed cell divisions (Zadrag et al, 2006;Zadrag-Tecza et al, 2009;Yang et al, 2011). We propose to call this volume the maximal volume.…”

“…Therefore, irrespective of their initial volume they all enter their first S phase of the cell cycle after reaching this threshold value. Taking into account that maximal volume is constant for cells of the same genetic background (Zadrag et al, 2005(Zadrag et al, , 2006Zadrag-Tecza et al, 2009;Yang et al, 2011), the maximal number of daughter cells formed (maximal rls) depends mainly on the rate of cell volume increase during one cycle.…”

A growing role for hypertrophy in senescence

“…The key point in this debate centers around whether increased cell size and/or hypertrophy actually reduces RLS or is merely correlative with senescence in yeast. To date, four experiments favor a causative role for increased cell size and/or hypertrophy in senescence Zadrag et al, 2006;Zadrag-Tecza et al, 2008;Yang et al, 2011). First, although initial experiments with alpha factor demonstrated that RLS was not reduced despite increased size (Kennedy et al, 1994), follow-up experiments have concluded the opposite (Zadrag et al, 2006;Bilinski et al, 2012a, b).…”