Bioprospecting of sourdough microbial species from artisan bakeries in the city of Valencia.

This work describes the characterization of an artisanal sourdough set of bakeries located in the city of Valencia. Culture-dependent and -independent analyses detected Fructilactobacillus sanfranciscensis, Saccharomyces cerevisiae and Kazachstania humilis as dominant species. Nevertheless, specific technological parameters, including backslopping temperature, dough yield, or the addition of salt affected microbial counting, LAB/Yeast ratio, and gassing performance, favouring the appearance of several species of Lactobacillus sp., Limosilactobacillus pontis or Torulaspora delbrueckii as additional players. Sourdough leavening activity was affected positively by yeast counts and negatively by the presence of salt. In addition, the predominance of a particular yeast species appeared to impact the dynamics of CO2 release. Seven important flavour-active compounds (ethyl acetate, 1-hexanol, 2-penthylfuran, 3-ethyl-2-methyl-1,3-hexadiene, 2-octen-1-ol, nonanal and 1-nonanol) were detected in all samples and together with 3-methyl butanol and hexyl acetate represented more than the 53% of volatile abundancy in nine of the ten sourdoughs analysed. Even so, the specific microbial composition of each sample influenced the volatile profile. For example, the occurrence of K. humilis or S. cerevisiae as dominant yeast influenced the composition of major alcohol species, while F. sanfranciscensis and L. pontis positively correlated with aldehydes and octanoic acid content. In addition, relevant correlations could be also found among different technological parameters and between these, volatile compounds and microbial species. Overall, our study emphasises on how differences in technological parameters generate biodiversity in a relatively small set of artisan sourdoughs providing opportunities for excellence and quality baking products.

Inappropriate translation inhibition and P-body formation cause cold-sensitivity in tryptophan-auxotroph yeast mutants.

In response to different adverse conditions, most eukaryotic organisms, including Saccharomyces cerevisiae, downregulate protein synthesis through the phosphorylation of eIF2α (eukaryotic initiation factor 2α) by Gcn2, a highly conserved protein kinase. Gcn2 also controls the translation of Gcn4, a transcription factor involved in the induction of amino acid biosynthesis enzymes. Here, we have studied the functional role of Gcn2 and Gcn2-regulating proteins, in controlling translation during temperature downshifts of TRP1 and trp1 yeast cells. Our results suggest that neither cold-instigated amino acid limitation nor Gcn2 are involved in the translation suppression at low temperature. However, loss of TRP1 causes increased eIF2α phosphorylation, Gcn2-dependent polysome disassembly and overactivity of Gcn4, which result in cold-sensitivity. Indeed, knock-out of GCN2 improves cold growth of trp1 cells. Likewise, mutation of several Gcn2-regulators and effectors results in cold-growth effects. Remarkably, we found that Hog1, the osmoresponsive MAPK, plays a role in the regulatory mechanism of Gcn2-eIF2α. Finally, we demonstrated that P-body formation responds to a downshift in temperature in a TRP1-dependent manner and is required for cold tolerance.

Sng1 associates with Nce102 to regulate the yeast Pkh-Ypk signalling module in response to sphingolipid status.

All cells are delimited by biological membranes, which are consequently a primary target of stress-induced damage. Cold alters membrane functionality by decreasing lipid fluidity and the activity of membrane proteins. In Saccharomyces cerevisiae, evidence links sphingolipid homeostasis and membrane phospholipid asymmetry to the activity of the Ypk1/2 proteins, the yeast orthologous of the mammalian SGK1-3 kinases. Their regulation is mediated by different protein kinases, including the PDK1 orthologous Pkh1/2p, and requires the function of protein effectors, among them Nce102p, a component of the sphingolipid sensor machinery. Nevertheless, the mechanisms and the actors involved in Pkh/Ypk regulation remain poorly defined. Here, we demonstrate that Sng1, a transmembrane protein, is an effector of the Pkh/Ypk module and identify the phospholipid asymmetry as key for yeast cold adaptation. Overexpression of SNG1 impairs phospholipid flipping, reduces reactive oxygen species (ROS) and improves, in a Pkh-dependent manner, yeast growth in myriocin-treated cells, suggesting that excess Sng1p stimulates the Pkh/Ypk signalling. Furthermore, we link these effects to the association of Sng1p with Nce102p. Indeed, we found that Sng1p interacts with Nce102p both physically and genetically. Moreover, mutant nce102∆ sng1∆ cells show features of impaired Pkh/Ypk signalling, including increased ROS accumulation, reduced life span and defects in Pkh/Ypk-controlled regulatory pathways. Finally, myriocin-induced hyperphosphorylation of Ypk1p and Orm2p, which controls sphingolipid homeostasis, does not occur in nce102∆ sng1∆ cells. Hence, both Nce102p and Sng1p participate in a regulatory circuit that controls the activity of the Pkh/Ypk module and their function is required in response to sphingolipid status.

Characterization of the S. cerevisiae inp51 mutant links phosphatidylinositol 4,5-bisphosphate levels with lipid content, membrane fluidity and cold growth.

Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and its derivatives diphosphoinositol phosphates (DPIPs) play key signaling and regulatory roles. However, a direct function of these molecules in lipid and membrane homeostasis remains obscure. Here, we have studied the cold tolerance phenotype of yeast cells lacking the Inp51-mediated phosphoinositide-5-phosphatase. Genetic and biochemical approaches showed that increased metabolism of PI(4,5)P2 reduces the activity of the Pho85 kinase by increasing the levels of the DPIP isomer 1-IP7. This effect was key in the cold tolerance phenotype. Indeed, pho85 mutant cells grew better than the wild-type at 15 °C, and lack of this kinase abolished the inp51-mediated cold phenotype. Remarkably, reduced Pho85 function by loss of Inp51 affected the activity of the Pho85-regulated target Pah1, the yeast phosphatidate phosphatase. Cells lacking Inp51 showed reduced Pah1 abundance, derepression of an INO1-lacZ reporter, decreased content of triacylglycerides and elevated levels of phosphatidate, hallmarks of the pah1 mutant. However, the inp51 phenotype was not associated to low Pah1 activity since deletion of PAH1 caused cold sensitivity. In addition, the inp51 mutant exhibited features not shared by pah1, including a 40%-reduction in total lipid content and decreased membrane fluidity. These changes may influence the activity of membrane-anchored and/or associated proteins since deletion of INP51 slows down the transit to the vacuole of the fluorescent dye FM4-64. In conclusion, our work supports a model in which changes in the PI(4,5)P2 pool affect the 1-IP7 levels modulating the activity of Pho85, Pah1 and likely additional Pho85-controlled targets, and regulate lipid composition and membrane properties.

How can lifeguards recover better? A cross-over study comparing resting, running, and foam rolling.

PURPOSE: The aim of this study is to compare the effectiveness of active recovery in form of running or foam rolling on clearing blood lactate compared to remain sitting after a water rescue. METHOD: A quasi experimental cross-over design was used to test the effectiveness of two active recovery methods: foam rolling (FR) and running (RR), compared with passive recovery (PR) on the blood lactate clearance after performing a water rescue. Twelve lifeguards from Marín (Pontevedra) completed the study. The participants performed a 100-meter water rescue and a 25-minute recovery protocol. RESULTS: The post recovery lactate levels were significantly lower for foam rolling (4.4±1.5mmol/l, P=0.005, d=0.94) and running (4.9±2.3mmol/l, P=0.027, d=1.21) compared with resting (7.2±2.5mmol/l); there was no significant difference between foam rolling and running (P=1.000). CONCLUSIONS: We found that surf lifesavers clear out blood lactate more efficient when performing an active recovery protocol. Foam rolling is an effective method of increasing the rate of blood lactate clearance. These two recovery methods are also adequate for surf lifeguards as they do not interfere with the surveillance aspect of their job.

Reiterative epoxide-based strategies for the synthesis of stereo-n-ads and application to polypropionate synthesis. A Personal Account.

The enantioselective synthesis of polypropionates continues to be an attractive realm for the synthetic chemists mostly due to the challenges presented by the number of consecutive stereogenic centers contained within the aliphatic chain. Over the years, our laboratory has developed an epoxide-based three-step reiterative methodology for the construction of these targets, with the ultimate goal that the approach could be extended to the synthesis of polypropionate-containing natural products. The key steps include the diastereoselective epoxidation of allylic and homoallylic alcohols, and the regioselective cleavage of 2-methyl-3,4-epoxy alcohols. The choice of the organometallic reagent, and the cis/trans geometry of the chiral epoxide can be used to control both the relative and absolute configuration of the resulting propionate unit, allowing our approach to be applied in the synthesis of advanced fragments. Additionally, the combination of our first- and second-generation methodologies permits the incorporation of different variations at the methyl moiety.

Protein kinase Snf1 is involved in the proper regulation of the unfolded protein response in Saccharomyces cerevisiae.

Glc7 is the only catalytic subunit of the protein phosphatase type 1 in the yeast S. cerevisiae and, together with its regulatory subunits, is involved in many essential processes. Analysis of the non-essential mutants in the regulatory subunits of Glc7 revealed that the lack of Reg1, and no other subunit, causes hypersensitivity to unfolded protein response (UPR)-inducers, which was concomitant with an augmented UPR element-dependent transcriptional response. The Glc7-Reg1 complex takes part in the regulation of the yeast AMP-activated serine/threonine protein kinase Snf1 in response to glucose. We demonstrate in the present study that the observed phenotypes of reg1 mutant cells are attributable to the inappropriate activation of Snf1. Indeed, growth in the presence of limited concentrations of glucose, where Snf1 is active, or expression of active forms of Snf1 in a wild-type strain increased the sensitivity to the UPR-inducer tunicamycin. Furthermore, reg1 mutant cells showed a sustained HAC1 mRNA splicing and KAR2 mRNA levels during the recovery phase of the UPR, and dysregulation of the Ire1-oligomeric equilibrium. Finally, overexpression of protein phosphatases Ptc2 and Ptc3 alleviated the growth defect of reg1 cells under endoplasmic reticulum (ER) stress conditions. Altogether, our results reveal that Snf1 plays an important role in the attenuation of the UPR, as well as identifying the protein kinase and its effectors as possible pharmacological targets for human diseases that are associated with insufficient UPR activation.

Genista anglica (Fabaceae): One very diverse species or one species complex?

Genista anglica represents a widely distributed group of shrubs in the Iberian Peninsula, as well as in the North of the Moroccan Mountains, the South of Italy and in most oceanic territories of Western Europe, with its northern limit in Sweden. Up to five different species within the group have been described in these territories: Genista ancistrocarpa, G. acutifolia, G. brutia and G. silana, as well as G. anglica sensu stricto. The diversity of Genista anglica sensu lato as well as the phylogenetic patterns that have generated this diversity have been analyzed through the use of nuclear (ITS, ETS) and chloroplastic (trnL, trnL-F, rbcL, matK) DNA sequences. Our results show that the group probably originated in the West of the Iberian Peninsula and subsequently spread to the rest of the European oceanic territories. Additionally, the results support the idea that the presence of a group of plants in the South of Italy, where G. brutia and G. silana were previously described, has been the consequence of the introduction of seeds collected in the Northwest of the Iberian Peninsula. Our results also indicate that, in contrast to some authors, the populations from the West of the Iberian Peninsula are not isolated and, consequently, they should be grouped into one species with high diversity, therefore differentiation into different taxa is no longer adequate.

Impact of error self-perception of aerobic capacity in the safety and efficacy of the lifeguards.

INTRODUCTION: The strong physical demands that are required of lifeguards during rescues also require an accurate self-perception of one's fitness level to be able to regulate the intensity of effort. OBJECTIVES: The aim of this study was to determine the real aerobic capacity (RAC) and to compare it with two self-reported measurements: subjective appraisal of aerobic capacity (SAAC) and appraisal of physical exercise (APE). METHODS: Fifty-two professional lifeguards were included in the study. For an objective assessment of RAC, the lifeguards' maximum oxygen uptake (VO2max) values were measured during treadmill stress tests. A fitness assessment questionnaire was used to obtain the SAAC and APE values. RESULTS: We found a statistically significant association between the APE and RAC variables in the contingency analysis (p < 0.001). In total, 93.7% of the lifeguards who obtained a VO2max value below 43 ml kg(-1) min(-1) considered their aerobic capacity to be high or very high. CONCLUSION: This self-perception error of true aerobic capacity could lead to premature fatigue during a rescue, endangering both the lifeguard's life and the life of the victim. These data may help lifeguards and beach managers to become aware of the need to know lifeguards' true physical conditions through testing and structured training programs.

Crystal structure of (-)-(2R,3S,4R,5R)-5-(1,3-di-thian-2-yl)-3-methyl-1-(triiso-propyl-sil-yloxy)hexane-2,4-diol.

The title compound, C20H42O3S2Si, crystallized with two independent mol-ecules (A and B) in the asymmetric unit. They consist of syn,anti,anti-stereo-tetrads with a 1,3-di-thiane motif and a primary alcohol protected as the triisopropyl silyl ether. The 1,3-di-thiane ring adopts a chair conformation, while the rest of each mol-ecule displays a common zigzag conformation. There is an intra-molecular O-H⋯O hydrogen bond in each mol-ecule. In the crystal, the A and B mol-ecules are linked via O-H⋯O hydrogen bonds, forming -A-B-A--B-- chains along [010]. The absolute structure was determined by resonant scattering (anomalous scattering) [Flack parameter = 0.035 (8)].

Balancing Act: A Comprehensive Review of Vestibular Evaluation in Cochlear Implants.

Cochlear implantation, a transformative intervention for individuals with profound hearing loss, has evolved significantly over the years. However, its impact on the vestibular system, responsible for balance and spatial orientation, remains a subject of ongoing research and clinical consideration. This narrative review highlights key aspects of vestibular evaluation in patients undergoing cochlear implantation. Preoperative vestibular assessment is crucial to establish baseline vestibular function and identify any pre-existing balance issues. Various tests, including caloric, rotational chair, vestibular-evoked myogenic potential, and video head impulse tests, play a vital role in evaluating vestibular function. The goal is to assess the risk of vestibular disturbances arising from the surgery, guide surgical planning, and detect pre-existing alterations that could be totally or partially compensated. While some patients experience minimal vestibular disruptions, others may encounter transient or persistent balance issues following cochlear implant surgery. Postoperative vestibular testing allows for the early detection of such disturbances, enabling timely interventions like vestibular rehabilitation and evaluating changes produced due to surgical complications or changes in the patient's prior conditions. Challenges in vestibular evaluation include individual variability in patient responses, the proximity of the cochlea to the vestibular system, and the need to tailor testing protocols to individual needs. Further research is essential to refine testing protocols, minimize vestibular disturbances, and improve outcomes for cochlear implant candidates. A multidisciplinary approach involving otolaryngologists, audiologists, and physical therapists is integral to comprehensive patient care in this context. In conclusion, vestibular evaluation in patients undergoing cochlear implantation is critical for optimizing surgical planning, managing postoperative issues, and enhancing the overall quality of life for individuals embarking on the journey of restored hearing.

Sourdough Yeast Strains Exhibit Thermal Tolerance, High Fermentative Performance, and a Distinctive Aromatic Profile in Beer Wort.

The increasing popularity of home brewing and the fast evolution of craft beer companies have fuelled the interest in novel yeasts as the main actors diversifying the beer portfolio. Here, we have characterized the thermal tolerance and brewing-related features of two sourdough (SD) isolates of Saccharomyces cerevisiae, SDy01 and SDy02, at different temperatures, 20 and 37 °C, comparing them with commercial brew strains, AaB and kNB. The SD strains exhibited tolerance to the main brewing-related stress conditions and increased growth rates and lower lag phases than the reference beer strains at both temperatures. Consistent with this, SDy01 and SDy02 displayed higher fermentative activity in terms of sugar rate depletion and the release of metabolic by-products. Moreover, SDy01 and SDy02 brewing at 20 °C increased their total amount of volatile compounds (VOCs), in particular, their esters and carboxyl compounds, as compared to the reference AaB strain. In contrast, fermentation at 37 °C resulted in a drastic reduction in the number of VOCs in wort fermented with SD yeast, especially in its level of esters. In conclusion, our results stress the high fermentative performance of SD strains in beer wort and their ability to provide a complex and specific aromatic profile at a wide range of temperatures.

Shaping the curve from the microscopic transsphenoidal to the endoscopic endonasal approach for the sellar region.

OBJECTIVE: This study aimed to investigate the limitations, barriers, and complications in the early transition from the microscopic transsphenoidal approach (MTA) to the endonasal endoscopic approach (EEA) to the skull base in our institution. METHODS: Technical challenges, as well as clinical features and complications, were compared between MTA, EEA, and mixed cases during the early surgical curve. RESULTS: The period from the early learning curve was 1 year until the EEA protocol was used routinely. A total of 34 patients registered a resection using a transsphenoidal approach. Eighteen patients underwent EEA, 11 underwent MTA, and five underwent a mixed endonasal and microscopic approach. Non-significant differences were found in endocrine outcomes between the three groups. Patients with unchanged or improved visual function were higher in the EEA group (p = 0.147). Non-significant differences were found in terms of the extent of resection (EOR) between groups (p = 0.369). Only 1 (2.9%) patient in the whole series developed a post-operative CSF leaking that resolved with medical management, belonging to the EEA group (5.5%). CONCLUSIONS: The early phase of the learning curve did not affect our series significantly in terms of the EOR, endocrine status, and visual outcomes.

OBJETIVO: Investigar las limitaciones, las barreras y las complicaciones en la transición del abordaje transesfenoidal microscópico (ATM) al abordaje endonasal endoscópico (AEE) para la base del cráneo en nuestra institución. MÉTODO: Se compararon las características clínicas y las complicaciones entre ATM, AEE y casos mixtos durante la curva quirúrgica temprana. RESULTADOS: El periodo desde la curva de aprendizaje inicial fue de 1 año hasta que se utilizó el protocolo AEE de forma sistemática. Un total de 34 pacientes tuvieron una resección por vía transesfenoidal. A 18 pacientes se les realizó AEE, a 11 ATM y a 5 abordaje mixto endonasal y microscópico. Se encontraron diferencias no significativas en los resultados endocrinos entre los tres grupos. Los pacientes con función visual sin cambios o mejorada fueron más en el grupo AEE (p = 0.147). No se encontraron diferencias significativas respecto a la extensión de la resección (p = 0.369). Solo 1 (2.9%) paciente desarrolló una fístula de líquido cefalorraquídeo que se resolvió con manejo médico, perteneciente al grupo AEE (5.5%). CONCLUSIONES: La fase inicial de la curva de aprendizaje no afectó significativamente a nuestra serie en términos de extensión de la resección, estado endocrino y resultados visuales.

Low temperature highlights the functional role of the cell wall integrity pathway in the regulation of growth in Saccharomyces cerevisiae.

Unlike other stresses, the physiological significance and molecular mechanisms involved in the yeast cold response are largely unknown. In the present study, we show that the CWI (cell wall integrity) pathway plays an important role in the growth of Saccharomyces cerevisiae at low temperatures. Cells lacking the Wsc1p (wall integrity and stress response component 1) membrane sensor or the MAPKs (mitogen-activated protein kinases) Bck1p (bypass of C kinase 1), Mkk (Mapk kinase) 1p/Mkk2p or Slt2p (suppressor of lyt2) exhibited cold sensitivity. However, there was no evidence of either a cold-provoked perturbation of the cell wall or a differential cold expression program mediated by Slt2p. The results of the present study suggest that Slt2p is activated by different inputs in response to nutrient signals and mediates growth control through TORC1 (target of rapamycin 1 complex)-Sch9p (suppressor of cdc25) and PKA (protein kinase A) at low temperatures. We found that absence of TOR1 (target of rapamycin 1) causes cold sensitivity, whereas a ras2Δ mutant shows increased cold growth. Lack of Sch9p alleviates the phenotype of slt2Δ and bck1Δ mutant cells, as well as attenuation of PKA activity by overexpression of BCY1 (bypass of cyclase mutations 1). Interestingly, swi4Δ mutant cells display cold sensitivity, but the phenotype is neither mediated by the Slt2p-regulated induction of Swi4p (switching deficient 4)-responsive promoters nor influenced by osmotic stabilization. Hence, cold signalling through the CWI pathway has distinct features and might mediate still unknown effectors and targets.

The influence of age on aerobic capacity and health indicators of three rescue groups.

The aim of this study was to determine the relationship between age, aerobic capacity (V(O2max)) and other health indicators among 3 rescue groups. The type of training and the subjective perception of physical fitness obtained via the Assessment Questionnaire of Physical Fitness were also analysed. To obtain V(O2max), 37 firefighters, 22 lifeguards and 59 mine rescue workers had a treadmill test. Their body mass index and body fat percentage were also calculated. The results show a significant decline in V(O2max) of the older participants, which affects the effectiveness of rescue work. Furthermore, the training of all groups was inconsistent and based on individual needs. Variable training and the decline in V(O2max) with age affected the effectiveness of the rescue tasks of each group.

Adaptive laboratory evolution for acetic acid-tolerance matches sourdough challenges with yeast phenotypes.

Acetic acid tolerance of Saccharomyces cerevisiae is an important trait in sourdough fermentation processes, where the accumulation of acid by the growth of lactic acid bacteria reduces the yeast metabolic activity. In this work, we have carried out adaptive laboratory evolution (ALE) experiments in two sourdough isolates of S. cerevisiae exposed to acetic acid, or alternatively to acetic acid and myriocin, an inhibitor of sphingolipid biosynthesis that sped-up the evolutionary adaptation. Evolution approaches resulted in acetic tolerance, and surprisingly, increased lactic susceptibility. Four evolved clones, one from each parental strain and evolutionary scheme, were selected on the basis of their potential for CO2 production in sourdough conditions. Among them, two showed phenotypic instability characterized by strong lactic sensitivity after several rounds of growth under unstressed conditions, while two others, displayed increased constitutive acetic tolerance with no loss of growth in lactic medium. Genome sequencing and ploidy level analysis of all strains revealed aneuploidies, which could account for phenotypic heterogeneity. In addition, copy number variations (CNVs), affecting specially to genes involved in ion transport or flocculation, and single nucleotide polymorphisms (SNPs) were identified. Mutations in several genes, ARG82, KEX1, CTK1, SPT20, IRA2, ASG1 or GIS4, were confirmed as involved in acetic and/or lactic tolerance, and new determinants of these phenotypes, MSN5 and PSP2, identified.

Concise epoxide-based synthesis of the C14-C25 bafilomycin A(1) polypropionate chain.

An efficient non-aldol convergent synthesis of the C14-C25 polyketide fragment of bafilomycin A(1) was completed in 16% overall yield and 8 steps in its longest linear sequence. This synthesis highlights the formation of the key fragments using a three-step sequence of epoxide cleavage, alkyne reduction, and epoxidation developed in our laboratory; starting from suitably protected enantiomeric epoxides of trans-2,3-epoxybutanol. This chemistry represents a quick asymmetric and diastereoselective construction of the polyketide chain of bafilomycin A(1), in which every stereogenic center was constructed using solely epoxide chemistry.

Network Adaptive Deadband: NCS data flow control for shared networks.

This paper proposes a new middleware solution called Network Adaptive Deadband (NAD) for long time operation of Networked Control Systems (NCS) through the Internet or any shared network based on IP technology. The proposed middleware takes into account the network status and the NCS status, to improve the global system performance and to share more effectively the network by several NCS and sensor/actuator data flows. Relationship between network status and NCS status is solved with a TCP-friendly transport flow control protocol and the deadband concept, relating deadband value and transmission throughput. This creates a deadband-based flow control solution. Simulation and experiments in shared networks show that the implemented network adaptive deadband has better performance than an optimal constant deadband solution in the same circumstances.

Slt2 Is Required to Activate ER-Stress-Protective Mechanisms through TORC1 Inhibition and Hexosamine Pathway Activation.

Slt2, the MAPK of the cell wall integrity (CWI) pathway, connects different signaling pathways and performs different functions in the protective response of S. cerevisiae to stress. Previous work has evidenced the relation of the CWI pathway and the unfolded protein response (UPR), a transcriptional program activated upon endoplasmic reticulum (ER) stress. However, the mechanisms of crosstalk between these pathways and the targets regulated by Slt2 under ER stress remain unclear. Here, we demonstrated that ectopic expression of GFA1, the gene encoding the first enzyme in the synthesis of UDP-GlcNAc by the hexosamine biosynthetic pathway (HBP) or supplementation of the growth medium with glucosamine (GlcN), increases the tolerance of slt2 mutant cells to different ER-stress inducers. Remarkably, GlcN also alleviates the sensitivity phenotype of cells lacking IRE1 or HAC1, the main actors in controlling the UPR. The exogenous addition of GlcN reduced the abundance of glycosylated proteins and triggered autophagy. We also found that TORC1, the central stress and growth controller, is inhibited by tunicamycin exposure in cells of the wild-type strain but not in those lacking Slt2. Consistent with this, the tunicamycin-induced activation of autophagy and the increased synthesis of ATP in response to ER stress were absent by knock-out of SLT2. Altogether, our data placed Slt2 as an essential actor of the ER stress response by regulating the HBP activity and the TORC1-dependent signaling.

The activity of yeast Hog1 MAPK is required during endoplasmic reticulum stress induced by tunicamycin exposure.

Accumulation of unfolded proteins in the endoplasmic reticulum (ER) triggers the so-called unfolded protein response (UPR), a conserved signaling pathway that drives the transcription of genes such as chaperones and folding enzymes. Nevertheless, the activity of the UPR accounts only for a part of the gene expression program activated upon ER stress. Moreover, the mechanism(s) for how cells adapt and survive to this stress are largely unknown. Here, we show that the yeast high osmolarity glycerol (HOG) pathway plays a role in ER stress resistance. Strains lacking the MAPK Hog1p displayed sensitivity to tunicamycin or beta-mercaptoethanol, whereas hyperactivation of the pathway enhanced their resistance. However, these effects were not due to Hog1p-mediated regulation of the UPR. Northern blot analysis demonstrated that Hog1p controls the tunicamycin-induced transcriptional change of GPD1 and that wild-type cells exposed to the drug accumulated glycerol in a Hog1p-dependent manner. Consistent with this, deletion of genes involved in glycerol synthesis caused increased sensitivity to tunicamycin, whereas overexpression of GPD1 provided higher tolerance to both wild-type and hog1Delta mutant cells. Quite remarkably, these effects were mediated by the basal activity of the MAPK because tunicamycin exposure does not trigger the phosphorylation of Hog1p or its nuclear import. Hence, our results describe new aspects of the yeast response to ER stress and identify additional functions of glycerol and the Hog1p MAPK to provide stress resistance.