Germination and Outgrowth of Single Spores of
            <i>Saccharomyces cerevisiae</i>
            Viewed by Scanning Electron and Phase-Contrast Microscopy

Using high-resolution 13C nuclear magnetic resonance, we examined the mobilization of endogenous trehalose in suspensions of yeast asci. Sporulation of yeast cells in [1-13C]acetate resulted in incorporation of label into the C-3 and C-4 positions of trehalose within the asci. During germination of these asci with [1-3C]glucose, the consumption of both endogenous trehalose and exogenous glucose were followed simultaneously by 13C nuclear magnetic resonance, as was the formation of glycerol and ethanol, their glycolytic end products. Time courses for carbohydrate consumption indicated that trehalose, although it decreased to 25% of its initial value upon germination, was not preferentially catabolized and did not provide the primary energy supply for germination with glucose. The ratio of trehalose to glucose catabolized was 0.09. Exogenous glucose levels appeared to regulate trehalose mobilization since trehalose was only consumed when sufficiently high levels (>2 mM) of glucose were present. Upon glucose depletion newly synthesized [1-13C]trehalose was observed. Nuclear magnetic resonance spectra of extracts confirmed the trehalose peak assignments and showed products of [1-13C]glucose catabolism. In addition by quantitating trehalose consumption and 2-deoxyglucose incorporation in dormant yeast asci, we found that 3.8 + 0.4 molecules of 2-deoxyglucose were incorporated for each trehalose molecule consumed. Trehalose can therefore function as a carbohydrate source for ATP formation during dormancy.The disaccharide a,a-trehalose accumulates in spores of fungi in remarkably high concentrations (9, 11, 18). During yeast sporulation large quantities of trehalose are synthesized during acetate respiration in a nitrogen-limited medium. There are striking similarities to bacterial spores which contain high concentrations of 3-phosphoglycerate and dipicolinic acid (13). To generalize, it appears that in metabolically dormant spores large amounts of potential substrates for glycolysis are present as well as the full complement of glycolytic enzymes. In both bacteria and fungi these endogenous carbon sources decrease in concentration rapidly upon germination. Bacterial spores quickly catabolize 3-phosphoglycerate and release dipicolinic acid to the medium after heat shock and ionic stimulation (20).

Section: Resultssupporting

confidence: 65%

mentioning

confidence: 99%

13C nuclear magnetic resonance study of trehalose mobilization in yeast spores

Barton¹,

Hollander²,

Hopfield³

et al. 1982

“…5. Protein synthesis, followed by the incorporation of 3H-I,-phenylalanine, began at about 45 min after the onset of germination, (28). After 6 h (Tj in sporulation medium, a sample was withdrawn.…”

Section: Resultsmentioning

confidence: 99%

“…Canada Packers Limited, Toronto 9, Ontario, Canada. succinic acid synthetic medium (SSM) containing 1% Tween 80 (28). Germination and outgrowth were carried out and measured as previously described (28).…”

Section: Methodsmentioning

confidence: 99%

Macromolecular Synthesis During the Germination of Saccharomyces cerevisiae Spores

Rousseau

Halvorson

1973

Self Cite

After the dormancy of Saccharomyces cerevisiae ascospores had been broken, the synthesis of proteins was observed first, followed rapidly by synthesis of ribonucleic acid (RNA) and much later by deoxyribonucleic acid (DNA) synthesis. Phosphoglucomutase activity increased in a periodic (step) fashion, whereas the activity of five other enzymes increased linearly during germination and outgrowth. The rate of synthesis of these enzymes was highest at about the period of DNA replication. The amino acid pools of dormant spores contained high levels of proline, glutamic acid, and histidine. At 2 h after onset of germination, the pools of phenylalanine and methionine had disappeared and the other components had decreased significantly. By 3.5 h, with the exception of proline and cystine, most amino acid pool components had significantly increased.

“…These dramatic variations in glycogen and trehalose content, and the large absolute amounts that can be accumulated, suggest that these carbohydrates play important roles during the yeast life cycle. Indeed, studies correlating glycogen and trehalose levels with the physiological and developmental activities of the cells have suggested that these carbohydrates function as important carbon and energy reserves in starving cells (4,7,8,24), in cells undergoing respiratory adaptation (21,26,28,31), in sporulating cells (5,9,15), in germinating spores (15,34), in vegetative cells during emergence from stationary phase in fresh medium (24,39), and in cells traversing the mitotic cell cycle under conditions of carbon and energy limitation (19,20,41). Unfortunately, many of these studies are difficult to interpret in detail because they suffer from one or more of the following limitations: use of a strain that was not well characterized genetically; failure to measure extracellular glucose concentrations; inadequate characterization of the growth-limiting factors in the media used; inadequate characterization of the life cycle status of the cells (particularly the lack of reliable data on cell numbers); failure to measure both glycogen and trehalose; or use of a glycogen assay that seems to give spuriously high values (see Discussion).…”

mentioning

confidence: 99%

Reserve carbohydrate metabolism in Saccharomyces cerevisiae: responses to nutrient limitation

Lillie¹,

Pringle²

1980

759

361

The amounts of glycogen and trehalose have been measured in cells of a prototrophic diploid yeast strain subjected to a variety of nutrient limitations. Both glycogen and trehalose were accumulated in cells deprived specifically of nitrogen, sulfur, or phosphorus, suggesting that reserve carbohydrate accumulation is a general response to nutrient limitation. The patterns of accumulation and utilization of glycogen and trehalose were not identical under these conditions, suggesting that the two carbohydrates may play distinct physiological roles. Glycogen and trehalose were also accumulated by cells undergoing carbon and energy limitation, both during diauxic growth in a relatively poor medium and during the approach to stationary phase in a rich medium. Growth in the rich medium was shown to be carbon or energy limited or both, although the interaction between carbon source limitation and oxygen limitation was complex. In both media, the pattern of glycogen accumulation and utilization was compatible with its serving as a source of energy both during respiratory adaptation and during a subsequent starvation. In contrast, the pattern of trehalose accumulation and utilization seemed compatible only with the latter role. In cultures that were depleting their supplies of exogenous glucose, the accumulation of glycogen began at glucose concentrations well above those sufficient to suppress glycogen accumulation in cultures growing with a constant concentration of exogenous glucose. The mechanism of this effect is not clear, but may involve a response to the rapid rate of change in the glucose concentration.