Quantifying turgor pressure in budding and fission yeasts based upon osmotic properties

Lemière, Joël; Chang, Fred

doi:10.1101/2023.06.07.544129

“…In the limit of an extreme hyperosmotic shock, the re-105 maining cytoplasmic volume is comparable to the volume 106 of expelled water [14,21,31]. Thus, the total cytoplasmic 107 volume must be divided into a free volume and a bound 108 volume [32][33][34][35],…”

Section: Cell Growth 104mentioning

confidence: 99%

Physical constraints and biological regulations underlie universal osmoresponses

Ye,

Wang,

Lin

2024

Preprint

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Microorganisms constantly transition between environments with dramatically different external osmolarities. However, theories of microbial osmoresponses integrating physical constraints and biological regulation are lacking. Here, we propose such a theory, utilizing the separation of timescales for passive responses and biological regulations of osmolyte production and cell wall synthesis. We demonstrate that the two regulation strategies allow cells to adapt to a broad range of external osmolarity with a threshold value above which cells cannot grow, ubiquitous across bacteria and yeast. Intriguingly, the theory predicts a dramatic speedup of cell growth after an abrupt decrease in external osmolarity due to cell-wall synthesis regulation. Our theory rationalizes the unusually fast growth observed in fission yeast after an oscillatory osmotic perturbation, and the predicted growth rate peaks match quantitatively with experimental measurements. Our study reveals the physical basis of osmoresponse, yielding far-reaching implications for microbial physiology.

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Cytoplasmic fluidization contributes to breaking spore dormancy in fission yeast

Sakai,

Kondo,

Goto

et al. 2024

Proc. Natl. Acad. Sci. U.S.A.

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The cytoplasm is a complex, crowded environment that influences myriad cellular processes including protein folding and metabolic reactions. Recent studies have suggested that changes in the biophysical properties of the cytoplasm play a key role in cellular homeostasis and adaptation. However, it still remains unclear how cells control their cytoplasmic properties in response to environmental cues. Here, we used fission yeast spores as a model system of dormant cells to elucidate the mechanisms underlying regulation of the cytoplasmic properties. By tracking fluorescent tracer particles, we found that particle mobility decreased in spores compared to vegetative cells and rapidly increased at the onset of dormancy breaking upon glucose addition. This cytoplasmic fluidization depended on glucose-sensing via the cyclic adenosine monophosphate-protein kinase A pathway. PKA activation led to trehalose degradation through trehalase Ntp1, thereby increasing particle mobility as the amount of trehalose decreased. In contrast, the rapid cytoplasmic fluidization did not require de novo protein synthesis, cytoskeletal dynamics, or cell volume increase. Furthermore, the measurement of diffusion coefficients with tracer particles of different sizes suggests that the spore cytoplasm impedes the movement of larger protein complexes (40 to 150 nm) such as ribosomes, while allowing free diffusion of smaller molecules (~3 nm) such as second messengers and signaling proteins. Our experiments have thus uncovered a series of signaling events that enable cells to quickly fluidize the cytoplasm at the onset of dormancy breaking.

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Cytoplasmic fluidization triggers breaking spore dormancy in fission yeast

Sakai,

Kondo,

Goto

et al. 2023

Preprint

View full text Add to dashboard Cite

The cytoplasm is a complex, crowded environment that influences myriad cellular processes including protein folding and metabolic reactions. Recent studies have suggested that changes in the biophysical properties of the cytoplasm play a key role in cellular homeostasis and adaptation. However, it still remains unclear how cells control their cytoplasmic properties in response to environmental cues. Here, we used fission yeast spores as a model system of dormant cells to elucidate the mechanisms underlying regulation of the cytoplasmic properties. By tracking fluorescent tracer particles, we found that particle mobility decreased in spores compared to vegetative cells, and rapidly increased at the onset of dormancy breaking upon glucose addition. This cytoplasmic fluidization depended on glucose sensing via the cAMP-PKA pathway. PKA activation led to trehalose degradation through trehalase Ntp1, thereby increasing particle mobility as the amount of trehalose decreased. In contrast, the rapid cytoplasmic fluidization did not requirede novoprotein synthesis, cytoskeletal dynamics, or cell volume increase. Furthermore, the measurement of diffusion coefficients with tracer particles of different sizes suggests that the spore cytoplasm impedes the movement of larger protein complexes (40–150 nm) such as ribosomes, while allowing free diffusion of smaller molecules (∼3 nm) such as second messengers and signaling proteins. Our experiments have thus uncovered a series of signaling events that enable cells to quickly fluidize the cytoplasm at the onset of dormancy breaking.Significance statementCellular processes are influenced by the biophysical properties of the cytoplasm such as crowding and viscoelasticity. Although it has been suggested that cells tune the cytoplasmic properties in response to environmental changes, the molecular mechanisms remain unclear. Here, we used the dormant fission yeast spores and uncovered signaling pathways that facilitate cytoplasmic fluidization during dormancy breaking. Furthermore, we tracked the mobility of intracellular tracer particles, and found that the spore cytoplasm impedes the mobility of larger protein complexes, while allowing free diffusion of smaller molecules. These results suggest that small signaling proteins can diffuse relatively freely in the spore cytoplasm and have the ability to transmit dormancy breaking signals, while the motion of large complexes, such as ribosomes, is restricted.

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Quantifying turgor pressure in budding and fission yeasts based upon osmotic properties

Cited by 5 publications

References 74 publications

Physical constraints and biological regulations underlie universal osmoresponses

Physical constraints and biological regulations underlie universal osmoresponses

Cytoplasmic fluidization contributes to breaking spore dormancy in fission yeast

Cytoplasmic fluidization triggers breaking spore dormancy in fission yeast

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