The nucleolus is speculated to be a regulator of cellular senescence in numerous biological systems (Guarente, Genes Dev 11(19):2449–2455, 1997; Johnson et al., Curr Opin Cell Biol 10(3):332–338, 1998). In the budding yeast Saccharomyces cerevisiae, alterations in nucleolar architecture, the redistribution of nucleolar protein and the accumulation of extrachromosomal ribosomal DNA circles (ERCs) during replicative aging have been reported. However, little is known regarding rDNA stability and changes in nucleolar activity during chronological aging (CA), which is another yeast aging model used. In the present study, the impact of aberrant cell cycle checkpoint control (knock-out of BUB1, BUB2, MAD1 and TEL1 genes in haploid and diploid hemizygous states) on CA-mediated changes in the nucleolus was studied. Nucleolus fragmentation, changes in the nucleolus size and the nucleolus/nucleus ratio, ERC accumulation, expression pattern changes and the relocation of protein involved in transcriptional silencing during CA were revealed. All strains examined were affected by oxidative stress, aneuploidy (numerical rather than structural aberrations) and DNA damage. However, the bub1 cells were the most prone to aneuploidy events, which may contribute to observed decrease in chronological lifespan. We postulate that chronological aging may be affected by redox imbalance-mediated chromosome XII instability leading to both rDNA instability and whole chromosome aneuploidy. CA-mediated nucleolus fragmentation may be a consequence of nucleolus enlargement and/or Nop2p upregulation. Moreover, the rDNA content of chronologically aging cells may be a factor determining the subsequent replicative lifespan. Taken together, we demonstrated that the nucleolus state is also affected during CA in yeast.Electronic supplementary materialThe online version of this article (doi:10.1007/s10522-014-9499-y) contains supplementary material, which is available to authorized users.

Dimethyl sulfoxide (DMSO) is used as a cryoprotectant for the preservation of cells, including yeast, and as a solvent for chemical compounds. We report that DMSO induces oxidative stress in the yeast. Saccharomyces cerevisiae wt strain EG-103 and its mutants Δsod1, Δsod2, and Δsod1 Δsod2 were used. Yeast were subjected to the action of 1-14% DMSO for 1 h at 28 °C. DMSO induced a concentration-dependent inhibition of yeast growth, the effect being more pronounced for mutants devoid of SOD (especially Δsod1 Δsod2). Cell viability was compromised. DMSO-concentration-dependent activity loss of succinate dehydrogenase, a FeS enzyme sensitive to oxidative stress, was observed. DMSO enhanced formation of reactive oxygen species, estimated with dihydroethidine in a concentration-dependent manner, the effect being again more pronounced in mutants devoid of superoxide dismutases. The content of cellular glutathione was increased with increasing DMSO concentrations, which may represent a compensatory response. Membrane fluidity, estimated by fluorescence polarization of DPH, was decreased by DMSO. These results demonstrate that DMSO, although generally considered to be antioxidant, induces oxidative stress in yeast cells.

Climate change, and in particular the increase in temperature we are currently observing, can affect herbivorous insects. Aphids, as poikilothermic organisms, are directly exposed to temperature increases that influence their metabolism. Heat stress causes disturbances between the generations and the neutralization of reactive oxygen species (ROS). The aim of this work is focused on explaining how the aphid, using the example of Aphis pomi, responds to abiotic stress caused by temperature increase. The experiment was carried out under controlled conditions at three temperatures: 20, 25, and 28 °C. In the first stage, changes in the activity of enzymatic markers (superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), β-glucosidase, polyphenol oxidase (PPO), and peroxidase (POD)) were determined in aphid tissues, at each temperature. In the second stage, microcalorimetry monitored changes in heat emitted by aphids, at each temperature. Our results showed that A. pomi defense responses varied depending on temperature and were highest at 28 °C. The flexible activity of enzymes and increase in the metabolic rate played the role of adaptive mechanisms and ran more effectively at higher temperatures. The A. pomi thus protected itself against ROS excessive induction and the aphids were able to respond quickly to environmental stress.

No abstract

Despite many studies of the aging process, questions about key factors ensuring longevity have not yet found clear answers. Temperature seems to be one of the most important factors regulating lifespan. However, the genetic background may also play a key role in determining longevity. The aim of this study was to investigate the relationship between the temperature, genetic background (fruit fly origin), and metabolic rate on lifespan. Experiments were performed with the use of the wild type Drosophila melanogaster fruit flies originating from Australia, Canada, and Benin and the reference OregonR strain. The metabolic rate of D. melanogaster was measured at 20 °C, 25 °C, and 28 °C in an isothermal calorimeter. We found a strong negative relationship between the total heat flow and longevity. A high metabolic rate leads to increased aging in males and females in all strains. Furthermore, our results showed that temperature has a significant effect on fecundity and body weight. We also showed the usefulness of the isothermal calorimetry method to study the effect of environmental stress conditions on the metabolic activity of insects. This may be particularly important for the forecasting of impact of global warming on metabolic activity and lifespan of various insects.

Despite many controversies, the yeast Saccharomyces cerevisiae continues to be used as a model organism for the study of aging. Numerous theories and hypotheses have been created for several decades, yet basic mechanisms of aging have remained unclear. Therefore, the principal aim of this work is to propose a possible mechanism leading to increased longevity in yeast. In this paper, we suggest for the first time that there is a link between decreased metabolic activity, fertility and longevity expressed as time of life in yeast. Determination of reproductive potential and total lifespan with the use of fob1Δ and sfp1Δ mutants allows us to compare the “longevity” presented as the number of produced daughters with the longevity expressed as the time of life. The results of analyses presented in this paper suggest the need for a change in the definition of longevity of yeast by taking into consideration the time parameter. The mutants that have been described as “long-lived” in the literature, such as the fob1Δ mutant, have an increased reproductive potential but live no longer than their standard counterparts. On the other hand, the sfp1Δ mutant and the wild-type strain produce a similar number of daughter cells, but the former lives much longer. Our results demonstrate a correlation between the decreased efficiency of the translational apparatus and the longevity of the sfp1Δ mutant. We suggest that a possible factor regulating the lifespan is the rate of cell metabolism. To measure the basic metabolism of the yeast cells, we used the isothermal microcalorimetry method. In the case of sfp1Δ, the flow of energy, ATP concentration, polysome profile and translational fitness are significantly lower in comparison with the wild-type strain and the fob1Δ mutant.Electronic supplementary materialThe online version of this article (doi:10.1007/s11357-015-9868-8) contains supplementary material, which is available to authorized users.

The P-stalk represents a vital element within the ribosomal GTPaseassociated center, which represents a landing platform for translational GTPases. The eukaryotic P-stalk exists as a uL10-(P1-P2) 2 pentameric complex, which contains five identical C-terminal domains, one within each protein, and the presence of only one such element is sufficient to stimulate factor-dependent GTP hydrolysis in vitro and to sustain cell viability. The functional contribution of the P-stalk to the performance of the translational machinery in vivo, especially the role of P-protein multiplication, has never been explored. Here, we show that ribosomes depleted of P1/P2 proteins exhibit reduced translation fidelity at elongation and termination steps. The elevated rate of the decoding error is inversely correlated with the number of the P-proteins present on the ribosome. Unexpectedly, the lack of P1/P2 has little effect in vivo on the efficiency of other translational GTPase (trGTPase)-dependent steps of protein synthesis, including translocation. We have shown that loss of accuracy of decoding caused by P1/P2 depletion is the major cause of translation slowdown, which in turn affects the metabolic fitness of the yeast cell. We postulate that the multiplication of P-proteins is functionally coupled with the qualitative aspect of ribosome action, i.e., the recoding phenomenon shaping the cellular proteome.KEYWORDS ribosomal proteins, ribosomal stalk, ribosome A t the expense of energy from GTP hydrolysis, translational GTPases (trGTPases) confer the unidirectional trajectory for the translational apparatus, providing at the same time unique timing for individual steps (1, 2). The main landing platform for trGTPases is situated on the large ribosomal subunit called the GTPase-associated center (GAC), and it represents a universally conserved ribosomal element where stimulation of trGTPase catalytic activity takes place (3). The GAC consists of two main elements, a conserved fragment of rRNA called the sarcin-ricin loop (SRL) and a ribosomal stalk composed of ribosomal proteins, which form an oligomeric protein complex (4). The protein part of GAC, the ribosome stalk, can be divided into two functionally and evolutionarily distinct parts, the base of the stalk and its lateral elements. The stalk base is composed of conserved ribosomal proteins uL11 (former names L11 and L12 for prokaryotes and eukaryotes, respectively) and uL10 (former names L10 and P0), which anchor the stalk to the rRNA (5, 6). The lateral part of the stalk is built of dimeric complexes P1-P2 in eukaryotes/archaea or (bL12) 2 in prokaryotes (4, 7). Despite the lack of amino acid sequence conservation, the lateral stalk fulfils the same functions and has a similar structural architecture across all domains of life (8). P1/P2 and bL12 proteins are built of two domains. The globular N-terminal domain (NTD) is responsible for dimerization, whereas the highly acidic C-terminal domain (CTD) interacts with trGTPases (9, 10). However, the structure of the CTD in euk...

The lifespan of budding yeast cells is divided into two stages: reproductive and post-reproductive. The post-reproductive stage of the yeast's lifespan has never been characterized before. We have analyzed the influence of various mutations on the post-reproductive (PRLS) and replicative (RLS) lifespans. The results indicate that PRLS demonstrates an inverse relationship with RLS. The observed lack of differences in the total lifespan (TLS) (expressed in units of time) of strains differing up to five times in RLS (expressed in the number of daughters formed) suggests the necessity of revision of opinions concerning the use of yeast as a model organism of gerontology.