scholarly journals Cell size and growth rate are modulated by TORC2-dependent signals

2017 ◽  
Author(s):  
Rafael Lucena ◽  
Maria Alcaide-Gavilán ◽  
Katherine Schubert ◽  
Maybo He ◽  
Matthew Domnauer ◽  
...  
Keyword(s):  
Growth Rate ◽  
Cell Size ◽  
Nutrient Availability ◽  
Feedback Loop ◽  
Budding Yeast ◽  
Regulatory Subunit ◽  
Underlying Mechanisms

SummaryThe size of all cells, from bacteria to vertebrates, is proportional to the growth rate set by nutrient availability, but the underlying mechanisms are unknown. Here, we show that nutrients modulate TORC2 signaling, and that cell size is proportional to TORC2 signaling in budding yeast. The TORC2 network controls production of ceramide lipids, which play roles in signaling. We discovered that ceramide-dependent signals control both growth rate and cell size. Thus, cells that can not make ceramides fail to modulate their growth rate or size in response to changes in nutrients. PP2A associated with the Rts1 regulatory subunit (PP2ARts1) is embedded in a feedback loop that controls TORC2 signaling and plays an important role in mechanisms that modulate TORC2 signaling in response to nutrients. Together, the data suggest a model in which growth rate and cell size are mechanistically linked by ceramide-dependent signals arising from the TORC2 network.

scholarly journals PP2ARts1enforces a proportional relationship between cell size and growth rate

2018 ◽  
Author(s):  
Ricardo M. Leitao ◽  
Annie Pham ◽  
Quincy Okobi ◽  
Douglas R. Kellogg
Keyword(s):  
Growth Rate ◽  
Cell Size ◽  
Cell Cycle Progression ◽  
Mechanistic Explanation ◽  
Regulatory Subunit ◽  
Daughter Cells ◽  
Duration Of Mitosis ◽  
Proportional Relationship ◽  
Underlying Mechanisms ◽  
The Relationship

AbstractCell size is proportional to growth rate. Thus, cells growing slowly in poor nutrients can be nearly half the size of cells growing rapidly in rich nutrients. The relationship between cell size and growth rate appears to hold across all orders of life, yet the underlying mechanisms are unknown. In budding yeast, most growth occurs during mitosis, and the proportional relationship between cell size and growth rate is therefore enforced primarily by modulating growth in mitosis. When growth is slow, the duration of mitosis is increased to allow more time for growth, yet the amount of growth required to complete mitosis is reduced, leading to birth of small daughter cells. Previous studies found that PP2A associated with the Rts1 regulatory subunit (PP2ARts1) works in a TORC2-dependent feedback loop that sets cell size and growth rate to match nutrient availability. However, it was unknown whether PP2ARts1influences growth in mitosis. Here, we show that PP2ARts1is required for the proportional relationship between cell size and growth rate during mitosis. Moreover, nutrients and PP2ARts1influence the duration of mitosis, and thus the extent of growth in mitosis, via Wee1 and Pds1/securin, two conserved regulators of mitotic progression. Together, the data suggest a model in which the same global signals that set growth rate also set the critical amount of growth required for cell cycle progression, which would provide a simple mechanistic explanation for the proportional relationship between size and growth rate.

scholarly journals A conserved Lkb1 signaling axis modulates TORC2 signaling in budding yeast

2018 ◽  
Author(s):  
Maria Alcaide-Gavilán ◽  
Rafael Lucena ◽  
Katherine Schubert ◽  
Karen Artiles ◽  
Jessica Zapata ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Growth Rate ◽  
Cell Growth ◽  
Carbon Source ◽  
Cell Size ◽  
Nutrient Availability ◽  
Cell Cycle Progression ◽  
Budding Yeast ◽  
Small Cells ◽  
Cycle Progression

ABSTRACTNutrient availability, growth rate and cell size are closely linked. For example, in budding yeast, the rate of cell growth is proportional to nutrient availability, cell size is proportional to growth rate, and growth rate is proportional to cell size. Thus, cells grow slowly in poor nutrients and are nearly half the size of cells growing in rich nutrients. Moreover, large cells grow faster than small cells. A signaling network that surrounds Tor kinase complex 2 (TORC2) plays an important role in enforcing these proportional relationships. Cells that lack components of the TORC2 network fail to modulate their growth rate or size in response to changes in nutrient availability. Here, we show that budding yeast homologs of the Lkb1 tumor suppressor kinase are required for normal modulation of TORC2 signaling and in response to changes in carbon source. Lkb1 kinases activate Snf1/AMPK to initiate transcription of genes required for utilization of poor carbon sources. However, Lkb1 influences TORC2 signaling via a novel pathway that is independent of Snf1/AMPK. Of the three Lkb1 homologs in budding yeast, Elm1 plays the most important role in modulating TORC2. Elm1 activates a pair of related kinases called Gin4 and Hsl1. Previous work found that loss of Gin4 and Hsl1 causes cells to undergo unrestrained growth during a prolonged mitotic arrest, which suggests that play a role in linking cell cycle progression to cell growth. We found that Gin4 and Hsl1 also control the TORC2 network. In addition, Gin4 and Hsl1 are themselves influenced by signals from the TORC2 network, consistent with previous work showing that the TORC2 network constitutes a feedback loop. Together, the data suggest a model in which the TORC2 network sets growth rate in response to carbon source, while also relaying signals via Gin4 and Hsl1 that set the critical amount of growth required for cell cycle progression. This kind of close linkage between control of cell growth and size would suggest a simple mechanistic explanation for the proportional relationship between cell size and growth rate.

scholarly journals A Conserved PP2A Regulatory Subunit Enforces Proportional Relationships Between Cell Size and Growth Rate

Genetics ◽  
2019 ◽  
Vol 213 (2) ◽  
pp. 517-528 ◽  
Author(s):  
Ricardo M. Leitao ◽  
Akshi Jasani ◽  
Rafael A. Talavera ◽  
Annie Pham ◽  
Quincy J. Okobi ◽  
...  
Keyword(s):  
Growth Rate ◽  
Cell Size ◽  
Regulatory Subunit

scholarly journals Vegetative Reproduction Is More Advantageous Than Sexual Reproduction in a Canopy-Forming Clonal Macroalga under Ocean Warming Accompanied by Oligotrophication and Intensive Herbivory

Plants ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1522
Author(s):  
Hikaru Endo ◽  
Toru Sugie ◽  
Yukiko Yonemori ◽  
Yuki Nishikido ◽  
Hikari Moriyama ◽  
...  
Keyword(s):  
Growth Rate ◽  
High Temperature ◽  
Nutrient Availability ◽  
Vegetative Reproduction ◽  
Ocean Warming ◽  
Regeneration Ability ◽  
Combined Effects ◽  
Regeneration Rate ◽  
Fish Herbivory ◽  
C 30

Ocean warming and the associated changes in fish herbivory have caused polarward distributional shifts in the majority of canopy-forming macroalgae that are dominant in temperate Japan, but have little effect on the alga Sargassum fusiforme. The regeneration ability of new shoots from holdfasts in this species may be advantageous in highly grazed environments. However, little is known about the factors regulating this in Sargassum species. Moreover, holdfast tolerance to high-temperature and nutrient-poor conditions during summer has rarely been evaluated. In the present study, S. fusiforme holdfast responses to the combined effects of temperature and nutrient availability were compared to those of sexually reproduced propagules. The combined effects of holdfast fragmentation and irradiance on regeneration were also evaluated. Propagule growth rate values changed from positive to negative under the combination of elevated temperature (20 °C–30 °C) and reduced nutrient availability, whereas holdfasts exhibited a positive growth rate even at 32 °C in nutrient-poor conditions. The regeneration rate increased with holdfast fragmentation (1 mm segments), but was unaffected by decreased irradiance. These results suggest that S. fusiforme holdfasts have a higher tolerance to high-temperature and nutrient-poor conditions during summer than propagules, and regenerate new shoots even if 1-mm segments remain in shaded refuges for fish herbivory avoidance.

scholarly journals A potential feedback loop underlying glacial-interglacial cycles

2021 ◽  
Author(s):  
Els Weinans ◽  
Anne Willem Omta ◽  
George A. K. van Voorn ◽  
Egbert H. van Nes
Keyword(s):  
Ocean Circulation ◽  
Feedback Loop ◽  
Atmospheric Temperature ◽  
Earth System ◽  
Biological Productivity ◽  
Ocean Ventilation ◽  
The Earth ◽  
Main Driver ◽  
Underlying Mechanisms ◽  
Convergent Cross Mapping

AbstractThe sawtooth-patterned glacial-interglacial cycles in the Earth’s atmospheric temperature are a well-known, though poorly understood phenomenon. Pinpointing the relevant mechanisms behind these cycles will not only provide insights into past climate dynamics, but also help predict possible future responses of the Earth system to changing CO$$_2$$ 2 levels. Previous work on this phenomenon suggests that the most important underlying mechanisms are interactions between marine biological production, ocean circulation, temperature and dust. So far, interaction directions (i.e., what causes what) have remained elusive. In this paper, we apply Convergent Cross-Mapping (CCM) to analyze paleoclimatic and paleoceanographic records to elucidate which mechanisms proposed in the literature play an important role in glacial-interglacial cycles, and to test the directionality of interactions. We find causal links between ocean ventilation, biological productivity, benthic $$\delta ^{18}$$ δ 18 O and dust, consistent with some but not all of the mechanisms proposed in the literature. Most importantly, we find evidence for a potential feedback loop from ocean ventilation to biological productivity to climate back to ocean ventilation. Here, we propose the hypothesis that this feedback loop of connected mechanisms could be the main driver for the glacial-interglacial cycles.

scholarly journals Proximate Factors Determining Age and Mass at Fledging in Rhinoceros Auklets (Cerorhinca Monocerata): Intra- and Interyear Variations

The Auk ◽  
2004 ◽  
Vol 121 (2) ◽  
pp. 452-462 ◽  
Author(s):  
Tomohiro Deguchi ◽  
Akinori Takahashi ◽  
Yutaka Watanuki
Keyword(s):  
Growth Rate ◽  
Wing Length ◽  
Linear Regression Analysis ◽  
Multiple Linear Regression Analysis ◽  
Major Effect ◽  
Timing Of Breeding ◽  
Hatching Date ◽  
Cerorhinca Monocerata ◽  
Parental Provisioning ◽  
Underlying Mechanisms

Abstract In alcids, growth rate and hatching date of chicks appear to affect fledging age and mass. Underlying mechanisms are hypothesized to be (1) critical wing length at fledging for postfledging survival, (2) synchronization of fledging to dilute predation risk, and (3) variable parental provisioning according to timing of breeding. To elucidate the effects of growth rate and hatching date on fledging age and mass, and to test those mechanistic hypotheses, we measured chick growth and fledging periods in Rhinoceros Auklets (Cerorhinca monocerata) at Teuri Island from 1995 to 2000. The multiple-linear regression analysis showed that intrayear variations of fledging age and mass were explained by growth rate or hatching date in five out of six years. Faster-growing chicks fledged younger and heavier, and earlier-hatched chicks fledged older and heavier. Consequently, no apparent correlation between fledging age and mass was observed in five out of six years. Analysis of interyear variation showed a negative correlation between fledging age and mass, which indicates that growth rates rather than hatching dates had a major effect. Wing length at fledging was independent of growth in mass. More than 80% of chicks fledged when they attained a narrow range of wing length (130–150 mm), presumably because they remained in their nests until they attained the critical wing length. In five out of six years, the chicks did not synchronize timing of fledging relative to timing of hatching. Later-hatched chicks attained lighter peak masses and at younger ages, which may indicate that their parents decreased provisioning rates when the chicks were still young. We suggest that (1) critical wing length at fledging and (2) variable parental provisioning according to timing of breeding could be underlying mechanisms determining these relationships between fledging age and mass.

scholarly journals Use of estradiol benzoate to limit triplets in a low dose FSH model of twinning

2021 ◽  
Author(s):  
weibin zeng ◽  
Lei An ◽  
Yanping Wang ◽  
Shuai Gao ◽  
Yusheng Qin ◽  
...  
Keyword(s):  
Growth Rate ◽  
Treatment Group ◽  
Feedback Loop ◽  
Production Efficiency ◽  
Low Dose ◽  
Follicle Stimulating Hormone ◽  
Estradiol Benzoate ◽  
Negative Feedback Loop ◽  
Beef Heifers ◽  
Excess Number

Abstract Background: Estrogen could limit the nondominant follicles development after the first deviation by inhibition of the FSH secretion through the negative feedback loop, which ensure that the number of dominant follicles would be in a moderate level. Methods: The objective of the present study was to evaluate the effect of estradiol benzoate (EB) on inhibiting the development of nondominant follicles and inducing twin calves in beef heifers. Beef heifers were synchronized using an estradiol (E2)- plus- progesterone (P4)- based and superovulated using small dose follicle- stimulating hormone (FSH) protocol. From days 6.5 to 7.5 every heifer was treated with variety dose of estradiol benzoate (EB) for 3 times with 12 h intervals to eliminate the excess number of dominant follicles. Results: The diameters of the two largest follicles (F1 and F2) continually increased from day 3.5 to day 10. However, the growth rate was constrained by exogenous EB, and the degree of suppression was greatest in the 0.5 mg EB treatment compared with other treatments. As a result, the number of large follicles (≥ 10 mm) was also reduced along with the dose of EB increased. The double/triple ovulations rate, pregnancy rate and twin were all demonstrate the highest in 0.2 mg EB treatment group than in other treatments. Conclusions：The present study describes an efficient protocol that can be used to stimulate the development of a small number of dominant follicles i.e. 2-3 at the deviation stage through a FSH and 0.2 mg EB combine treatment, which can further result in the production of two calves. The appropriate dose of EB treatment during FSH induced superovulation procedure could limit the number of dominant follicles development and eventually increase the calf production efficiency.

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