Physiological regulation of yeast cell death in multicellular colonies is triggered by ammonia

The existence of programmed cell death (PCD) in yeast and its significance to simple unicellular organisms is still questioned. However, such doubts usually do not reflect the fact that microorganisms in nature exist predominantly within structured, multicellular communities capable of differentiation, in which a profit of individual cells is subordinated to a profit of populations. In this study, we show that some PCD features naturally appear during the development of multicellular Saccharomyces cerevisiae colonies. An ammonia signal emitted by aging colonies triggers metabolic changes that localize yeast death only in the colony center. The remaining population can exploit the released nutrients and survives. In colonies defective in Sok2p transcription factor that are unable to produce ammonia (Váchová, L., F. Devaux, H. Kucerova, M. Ricicova, C. Jacq, and Z. Palková. 2004. J. Biol. Chem. 279:37973–37981), death is spread throughout the whole population, thus decreasing the lifetime of the colony. The absence of Mca1p metacaspase or Aif1p orthologue of mammalian apoptosis-inducing factor does not prevent regulated death in yeast colonies

In Vivo Determination of Organellar pH Using a Universal Wavelength-Based Confocal Microscopy Approach

Many essential cellular processes are affected by transmembrane H+ gradients and intracellular pH (pHi). The research of such metabolic events calls for a non-invasive method to monitor pHi within individual subcellular compartments. We present a novel confocal microscopy approach for the determination of organellar pHi in living cells expressing pH-dependent ratiometric fluorescent proteins. Unlike conventional intensity-based fluorometry, our method relies on emission wavelength scans at single-organelle resolution to produce wavelength-based pH estimates both accurate and robust to low-signal artifacts. Analyses of Ato1p-pHluorin and Ato1p-mCherry yeast cells revealed previously unreported wavelength shifts in pHluorin emission which, together with ratiometric mCherry, allowed for high-precision quantification of actual physiological pH values and evidenced dynamic pHi changes throughout the different stages of yeast colony development. Additionally, comparative pH quantification of Ato1p-pHluorin and Met17p-pHluorin cells implied the existence of a significant pHi gradient between peripheral and internal cytoplasm of cells from colonies occurring in the ammonia-producing alkali developmental phase. Results represent a step forward in the study of pHi regulation and subcellular metabolic functions beyond the scope of this study

Global changes in gene expression associated with phenotypic switching of wild yeast

BACKGROUND: Saccharomyces cerevisiae strains isolated from natural settings form structured biofilm colonies that are equipped with intricate protective mechanisms. These wild strains are able to reprogram themselves with a certain frequency during cultivation in plentiful laboratory conditions. The resulting domesticated strains switch off certain protective mechanisms and form smooth colonies that resemble those of common laboratory strains. RESULTS: Here, we show that domestication can be reversed when a domesticated strain is challenged by various adverse conditions; the resulting feral strain restores its ability to form structured biofilm colonies. Phenotypic, microscopic and transcriptomic analyses show that phenotypic transition is a complex process that affects various aspects of feral strain physiology; it leads to a phenotype that resembles the original wild strain in some aspects and the domesticated derivative in others. We specify the genetic determinants that are likely involved in the formation of a structured biofilm colonies. In addition to FLO11, these determinants include genes that affect the cell wall and membrane composition. We also identify changes occurring during phenotypic transitions that affect other properties of phenotypic strain-variants, such as resistance to the impact of environmental stress. Here we document the regulatory role of the histone deacetylase Hda1p in developing such a resistance. CONCLUSIONS: We provide detailed analysis of transcriptomic and phenotypic modulations of three related S. cerevisiae strains that arose by phenotypic switching under diverse environmental conditions. We identify changes specifically related to a strain’s ability to create complex structured colonies; we also show that other changes, such as genome rearrangement(s), are unrelated to this ability. Finally, we identify the importance of histone deacetylase Hda1p in strain resistance to stresses

Multilevel regulation of an α-arrestin by glucose depletion controls hexose transporter endocytosis

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Interactions of heterologous DNA with polyomavirus major structural protein, VP1

Abstract`Empty' polyomavirus pseudocapsids, self-assembled from the major structural protein VP1, bind DNA non-specifically and can deliver it into the nuclei of mammalian cells for expression [Forstová et al. (1995) Hum. Gene Ther. 6, 297–306]. Formation of suitable VP1-DNA complexes appears to be the limiting step in this route of gene delivery. Here, the character of VP1-DNA interactions has been studied in detail. Electron microscopy revealed that VP1 pseudocapsids can create in vitro at least two types of interactions with double-stranded DNA: (i) highly stable complexes, requiring free DNA ends, where the DNA is partially encapsidated; and, (ii) weaker interactions of pseudocapsids with internal parts of the DNA chain

The bZIP Transcription Factor Rca1p Is a Central Regulator of a Novel CO2 Sensing Pathway in Yeast

Like many organisms the fungal pathogen Candida albicans senses changes in the environmental CO2 concentration. This response involves two major proteins: adenylyl cyclase and carbonic anhydrase (CA). Here, we demonstrate that CA expression is tightly controlled by the availability of CO2 and identify the bZIP transcription factor Rca1p as the first CO2 regulator of CA expression in yeast. We show that Rca1p upregulates CA expression during contact with mammalian phagocytes and demonstrate that serine 124 is critical for Rca1p signaling, which occurs independently of adenylyl cyclase. ChIP-chip analysis and the identification of Rca1p orthologs in the model yeast Saccharomyces cerevisiae (Cst6p) point to the broad significance of this novel pathway in fungi. By using advanced microscopy we visualize for the first time the impact of CO2 build-up on gene expression in entire fungal populations with an exceptional level of detail. Our results present the bZIP protein Rca1p as the first fungal regulator of carbonic anhydrase, and reveal the existence of an adenylyl cyclase independent CO2 sensing pathway in yeast. Rca1p appears to regulate cellular metabolism in response to CO2 availability in environments as diverse as the phagosome, yeast communities or liquid culture

Proizvodnja i percepcija govora

Zbornik radova okupio je 57 domaćih i inozemnih autora/ica, koji/e kroz 33 rada, iz različitih istraživačkih kutova, obrađuju recentne teme o proizvodnji i percepciji govora, te o njihovoj međuovisnosti u govornom procesu. Knjiga je posvećena profesoru Damiru Horgi povodom njegova sedamdesetog rođendana. Uz svaki rad naveden je sažetak na hrvatskom i engleskom jeziku. Zbornik je objavljen u suizdavaštvu Odsjeka za fonetiku Filozofskog fakulteta Sveučilišta u Zagrebu, Odjela za fonetiku Hrvatskoga filološkog društva i FF-pressa.Zbornik radova okupio je 57 domaćih i inozemnih autora/ica, koji/e kroz 33 rada, iz različitih istraživačkih kutova, obrađuju recentne teme o proizvodnji i percepciji govora, te o njihovoj međuovisnosti u govornom procesu. Knjiga je posvećena profesoru Damiru Horgi povodom njegova sedamdesetog rođendana. Uz svaki rad naveden je sažetak na hrvatskom i engleskom jeziku. Zbornik je objavljen u suizdavaštvu Odsjeka za fonetiku Filozofskog fakulteta Sveučilišta u Zagrebu, Odjela za fonetiku Hrvatskoga filološkog društva i FF-pressa

Proizvodnja i percepcija govora

Zbornik radova okupio je 57 domaćih i inozemnih autora/ica, koji/e kroz 33 rada, iz različitih istraživačkih kutova, obrađuju recentne teme o proizvodnji i percepciji govora, te o njihovoj međuovisnosti u govornom procesu. Knjiga je posvećena profesoru Damiru Horgi povodom njegova sedamdesetog rođendana. Uz svaki rad naveden je sažetak na hrvatskom i engleskom jeziku. Zbornik je objavljen u suizdavaštvu Odsjeka za fonetiku Filozofskog fakulteta Sveučilišta u Zagrebu, Odjela za fonetiku Hrvatskoga filološkog društva i FF-pressa.Zbornik radova okupio je 57 domaćih i inozemnih autora/ica, koji/e kroz 33 rada, iz različitih istraživačkih kutova, obrađuju recentne teme o proizvodnji i percepciji govora, te o njihovoj međuovisnosti u govornom procesu. Knjiga je posvećena profesoru Damiru Horgi povodom njegova sedamdesetog rođendana. Uz svaki rad naveden je sažetak na hrvatskom i engleskom jeziku. Zbornik je objavljen u suizdavaštvu Odsjeka za fonetiku Filozofskog fakulteta Sveučilišta u Zagrebu, Odjela za fonetiku Hrvatskoga filološkog društva i FF-pressa