Publications (6)19.58 Total impact
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Article: Proteomic changes in response to potassium starvation in the extremophilic yeast Debaryomyces hansenii.
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ABSTRACT: In this work, we performed for the first time a proteomic approach to the processes induced by long-term potassium starvation in the halotolerant yeast Debaryomyces hansenii. The proteomic profile under this ionic stress conditions shows that important changes in gene expression take place as an adaptive response. We found a significant protein expression repression as well as metabolic changes such as the inhibition of the upper part of the glycolysis, the amino acid synthesis, and the Krebs cycle. On the other hand, genes related to stress responses, protein degradation, and sterols synthesis were upregulated in response to potassium deprivation. The findings in this study provide important information about how this particular yeast copes with ionic stress at molecular levels, which might further enrich the global understanding of salt tolerance processes in eukaryal systems and moreover highlighting the importance of the 'omics' approaches as a complement to the classical physiological studies.FEMS Yeast Research 05/2012; 12(6):651-61. · 2.40 Impact Factor -
Article: Monovalent cations regulate expression and activity of the Hak1 potassium transporter in Debaryomyces hansenii.
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ABSTRACT: Debaryomyces hansenii was able to grow in a medium containing residual amounts of K(+), indicating the activity of high affinity K(+) transporters. Transcriptional regulation analysis of the genes encoding the two potassium uptake systems in D. hansenii revealed that while DhTRK1 is not regulated at transcriptional level, expression of DhHAK1 required starvation in the absence of K(+) and Na(+) and was not affected by changes in membrane potential. Rb(+) transport in cells expressing DhHAK1 was activated by external Na(+) or acidic pH and inhibited by high pH. We propose a K(+)-H(+) symporter that, under certain conditions may work as a K(+)-Na(+) transporter, as the mechanism driving K(+) influx mediated by DhHak1p.Fungal Genetics and Biology 02/2011; 48(2):177-84. · 3.74 Impact Factor -
Article: Lack of main K+ uptake systems in Saccharomyces cerevisiae cells affects yeast performance in both potassium-sufficient and potassium-limiting conditions.
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ABSTRACT: A new YNB medium containing very low concentrations of alkali metal cations has been developed to carry out experiments to study potassium homoeostasis. Physiological characterization of Saccharomyces cerevisiae BY4741 strain and the corresponding mutant lacking the main potassium uptake systems (trk1 trk2) under potassium nonlimiting and limiting concentrations was performed, and novel important differences between both strains were found. At nonlimiting concentrations of KCl, the two strains had a comparable cell size and potassium content. Nevertheless, mutants were hyperpolarized, had lower pH and extruded fewer protons compared with the BY4741 strain. Upon transfer to K(+)-limiting conditions, cells of both strains became hyperpolarized and their cell volume and K(+) content diminished; however, the decrease was more relevant in BY4741. In low potassium, trk1 trk2 cells were not able to accomplish the cell cycle to the same extent as in BY4741. Moreover, K(+) limitation triggered a high-affinity K(+)/Rb(+) uptake process only in BY4741, with the highest affinity being reached as soon as 30 min after transfer to potassium-limiting conditions. By establishing basic cellular parameters under standard growth conditions, this work aims to establish a basis for the investigation of potassium homoeostasis at the system level.FEMS Yeast Research 08/2010; 10(5):508-17. · 2.40 Impact Factor -
Article: Analysis of a novel calcium auxotrophy in Aspergillus nidulans.
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ABSTRACT: In Aspergillus nidulans a combination of null mutations in halA, encoding a protein kinase, and sltA, encoding a zinc-finger transcription factor having no yeast homologues, results in an elevated calcium requirement ('calcium auxotrophy') without impairing net calcium uptake. sltA(-) (+/-halA(-)) mutations result in hypertrophy of the vacuolar system. In halA(-)sltA(-) (and sltA(-)) strains, transcript levels for pmcA and pmcB, encoding vacuolar Ca(2+)-ATPase homologues, are highly elevated, suggesting a regulatory relationship between vacuolar membrane area and certain vacuolar membrane ATPase levels. Deletion of both pmcA and pmcB strongly suppresses the 'calcium auxotrophy'. Therefore the 'calcium auxotrophy' possibly results from excessive vacuolar calcium sequestration, causing cytosolic calcium deprivation. Null mutations in nhaA, homologous to Saccharomyces cerevisiae NHA1, encoding a plasma membrane Na(+)/H(+) antiporter effluxing Na(+) and K(+), and a non-null mutation in trkB, homologous to S. cerevisiae TRK1, encoding a plasma membrane high affinity K(+) transporter, also suppress the calcium auxotrophy.Fungal Genetics and Biology 07/2010; 47(7):647-55. · 3.74 Impact Factor -
Article: Ref2, a regulatory subunit of the yeast protein phosphatase 1, is a novel component of cation homoeostasis.
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ABSTRACT: Maintenance of cation homoeostasis is a key process for any living organism. Specific mutations in Glc7, the essential catalytic subunit of yeast protein phosphatase 1, result in salt and alkaline pH sensitivity, suggesting a role for this protein in cation homoeostasis. We screened a collection of Glc7 regulatory subunit mutants for altered tolerance to diverse cations (sodium, lithium and calcium) and alkaline pH. Among 18 candidates, only deletion of REF2 (RNA end formation 2) yielded increased sensitivity to these conditions, as well as to diverse organic toxic cations. The Ref2F374A mutation, which renders it unable to bind Glc7, did not rescue the salt-related phenotypes of the ref2 strain, suggesting that Ref2 function in cation homoeostasis is mediated by Glc7. The ref2 deletion mutant displays a marked decrease in lithium efflux, which can be explained by the inability of these cells to fully induce the Na+-ATPase ENA1 gene. The effect of lack of Ref2 is additive to that of blockage of the calcineurin pathway and might disrupt multiple mechanisms controlling ENA1 expression. ref2 cells display a striking defect in vacuolar morphogenesis, which probably accounts for the increased calcium levels observed under standard growth conditions and the strong calcium sensitivity of this mutant. Remarkably, the evidence collected indicates that the role of Ref2 in cation homoeostasis may be unrelated to its previously identified function in the formation of mRNA via the APT (for associated with Pta1) complex.Biochemical Journal 12/2009; 426(3):355-64. · 4.90 Impact Factor -
Article: Oxidative stress sensitivity in Debaryomyces hansenii.
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ABSTRACT: Debaryomyces hansenii is an osmotolerant and halotolerant yeast of increasing interest for fundamental and applied research. In this work, we have performed a first study on the effect of oxidative stress on the performance of this yeast. We have used Saccharomyces cerevisiae as a well-known reference yeast. We show that D. hansenii is much more susceptible than S. cerevisiae to cadmium chloride, hydrogen peroxide or 1,4-dithiothreitol. These substances induced the formation of reactive oxygen species (ROS) in both yeasts, the amounts measured being significantly higher in the case of D. hansenii. We also show that NaCl exerted a protective effect against oxidative stress in Debaryomyces, but that this was not the case in Saccharomyces because sodium protected that yeast only when toxicity was induced with cadmium. On the basis of the present results, we raised the hypothesis that the sensitivity to oxidative stress in D. hansenii is related to the high amounts of ROS formed in that yeast and that observations such as low glutathione amounts, low basal superoxide dismutase and peroxidase activities, decrease in ATP levels produced in the presence of ROS inducers and high cadmium accumulation are determinants directly or indirectly involved in the sensitivity process.FEMS Yeast Research 04/2009; 9(4):582-90. · 2.40 Impact Factor
Top co-authors
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Institutions
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2009–2012
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University of Cordoba (Spain)
- Departamento de Microbiología
Córdoba, Andalusia, Spain
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2010–2011
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Universidad Católica de Córdoba
Córdoba, Provincia de Cordoba, Argentina
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