Journal of Fungi

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18 pages, 2208 KiB

Open AccessArticle

Ppn2 Polyphosphatase Improves the Ability of S. cerevisiae to Grow in Mild Alkaline Medium

by Irina A. Eliseeva, Lubov Ryazanova, Larisa Ledova, Anton Zvonarev, Airat Valiakhmetov, Maria Suntsova, Aleksander Modestov, Anton Buzdin, Dmitry N. Lyabin, Ivan V. Kulakovskiy and Tatiana Kulakovskaya

J. Fungi 2024, 10(11), 797; https://doi.org/10.3390/jof10110797 - 16 Nov 2024

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Abstract

Inorganic polyphosphates and respective metabolic pathways and enzymes are important factors for yeast active growth in unfavorable conditions. However, particular proteins of polyphosphate metabolism remain poorly explored in this context. Here we report biochemical and transcriptomic characterization of the CRN/PPN2 yeast strain (derived [...] Read more.

Inorganic polyphosphates and respective metabolic pathways and enzymes are important factors for yeast active growth in unfavorable conditions. However, particular proteins of polyphosphate metabolism remain poorly explored in this context. Here we report biochemical and transcriptomic characterization of the CRN/PPN2 yeast strain (derived from Ppn1-lacking CRN strain) overexpressing poorly studied Ppn2 polyphosphatase. We showed that Ppn2 overexpression significantly reduced lag phase in the alkaline medium presumably due to the ability of Ppn2 to efficiently hydrolyze inorganic polyphosphates and thus neutralize hydroxide ions in the cell. With RNA-Seq, we compared the molecular phenotypes of CRN/PPN2 and its parent CRN strain grown in YPD or alkaline medium and detected transcriptomic changes induced by Ppn2 overexpression and reflecting the adaptation to alkaline conditions. The core set of upregulated genes included several genes with a previously unknown function. Respective knockout strains (∆ecm8, ∆yol160w, ∆cpp3, ∆ycr099c) exhibited defects of growth or cell morphology in the alkaline medium, proving the functional involvement of the respective proteins in sustaining growth in alkaline conditions. Full article

(This article belongs to the Special Issue Stress Research in Filamentous Fungi and Yeasts)

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24 pages, 2094 KiB

Open AccessArticle

The Key Enzymes of Carbon Metabolism and the Glutathione Antioxidant System Protect Yarrowia lipolytica Yeast Against pH-Induced Stress

by Tatyana I. Rakhmanova, Natalia N. Gessler, Elena P. Isakova, Olga I. Klein, Yulia I. Deryabina and Tatyana N. Popova

J. Fungi 2024, 10(11), 747; https://doi.org/10.3390/jof10110747 - 29 Oct 2024

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Abstract

In this study, we first thoroughly assayed the response of the key enzymes of energy metabolism and the antioxidant system in Yarrowia lipolytica yeast at extreme pH. The activity of the tricarboxylic acid cycle enzymes, namely NAD-dependent isocitrate dehydrogenase, aconitate hydratase, NAD-dependent malate [...] Read more.

In this study, we first thoroughly assayed the response of the key enzymes of energy metabolism and the antioxidant system in Yarrowia lipolytica yeast at extreme pH. The activity of the tricarboxylic acid cycle enzymes, namely NAD-dependent isocitrate dehydrogenase, aconitate hydratase, NAD-dependent malate dehydrogenase, and fumarate hydratase, NADPH-producing enzymes of glucose-6-P dehydrogenase and NADP-dependent isocitrate dehydrogenase, and the enzymes of the glutathione system was assessed. All the enzymes that were tested showed a significant induction contrary to some decrease in the aconitate hydratase activity with acidic and alkaline stress. It is probable that a change in the enzyme activity in the mitochondria matrix is involved in the regulation of the cellular metabolism of Y. lipolytica, which allows the species to prosper at an extreme ambient pH. It distinguishes it from any other type of ascomycete. A close relationship between the induction of the Krebs cycle enzymes and the key enzymes of the glutathione system accompanied by an increased level of reduced glutathione was shown. The assumption that the increased activity of the Krebs cycle dehydrogenases and promotion of the pentose phosphate pathway at pH stress launches a set of events determining the adaptive response of Y. lipolytica yeast. Full article

(This article belongs to the Special Issue Stress Research in Filamentous Fungi and Yeasts)

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25 pages, 7826 KiB

Open AccessArticle

Regulation of Catalase Expression and Activity by DhHog1 in the Halotolerant Yeast Debaryomyces hansenii Under Saline and Oxidative Conditions

by Ileana de la Fuente-Colmenares, James González, Norma Silvia Sánchez, Daniel Ochoa-Gutiérrez, Viviana Escobar-Sánchez and Claudia Segal-Kischinevzky

J. Fungi 2024, 10(11), 740; https://doi.org/10.3390/jof10110740 - 26 Oct 2024

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Abstract

Efficient transcriptional regulation of the stress response is critical for microorganism survival. In yeast, stress-related gene expression, particularly for antioxidant enzymes like catalases, mitigates reactive oxygen species such as hydrogen peroxide (H₂O₂), preventing cell damage. The halotolerant yeast Debaryomyces [...] Read more.

Efficient transcriptional regulation of the stress response is critical for microorganism survival. In yeast, stress-related gene expression, particularly for antioxidant enzymes like catalases, mitigates reactive oxygen species such as hydrogen peroxide (H₂O₂), preventing cell damage. The halotolerant yeast Debaryomyces hansenii shows oxidative stress tolerance, largely due to high catalase activity from DhCTA and DhCTT genes. This study evaluates D. hansenii’s response to oxidative stress caused by H₂O₂ under saline conditions, focusing on cell viability, gene expression, and catalase activity. Chromatin organization in the promoter of DhCTA and DhCTT was analyzed, revealing low nucleosome occupancy in promoter regions, correlating with active gene expression. Stress-related motifs for transcription factors like Msn2/4 and Sko1 were found, suggesting regulation by the DhHog1 MAP kinase. Analysis of a Dhhog1Δ mutant showed DhHog1’s role in DhCTA expression under H₂O₂ or NaCl conditions. These findings highlight DhHog1’s critical role in regulating the stress response in D. hansenii, offering insights for enhancing stress tolerance in halotolerant yeasts, particularly for industrial applications in saline wastewater management. Full article

(This article belongs to the Special Issue Stress Research in Filamentous Fungi and Yeasts)

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18 pages, 6440 KiB

Open AccessArticle

Genome-Scale Screening of Saccharomyces cerevisiae Deletion Mutants to Gain Molecular Insight into Tolerance to Mercury Ions

by Jianing Xian, Leilei Ni, Chengkun Liu, Jiyang Li, Yuhang Cao, Jie Qin, Dongwu Liu and Xue Wang

J. Fungi 2024, 10(7), 492; https://doi.org/10.3390/jof10070492 - 16 Jul 2024

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Abstract

Mercury (Hg) is a global pollutant and a bioaccumulative toxin that seriously affects the environment. Though increasing information has been obtained on the mechanisms involved in mercury toxicity, there is still a knowledge gap between the adverse effects and action mechanisms, especially at [...] Read more.

Mercury (Hg) is a global pollutant and a bioaccumulative toxin that seriously affects the environment. Though increasing information has been obtained on the mechanisms involved in mercury toxicity, there is still a knowledge gap between the adverse effects and action mechanisms, especially at the molecular level. In the current study, we screened a diploid library of Saccharomyces cerevisiae single-gene deletion mutants to identify the nonessential genes associated with increased sensitivity to mercury ions. By genome-scale screening, we identified 64 yeast single-gene deletion mutants. These genes are involved in metabolism, transcription, antioxidant activity, cellular transport, transport facilitation, transport routes, and the cell cycle, as well as in protein synthesis, folding, modification, and protein destination. The concentration of mercury ions was different in the cells of yeast deletion mutants. Moreover, the disruption of antioxidant systems may play a key role in the mercurial toxic effects. The related functions of sensitive genes and signal pathways were further analyzed using bioinformatics-related technologies. Among 64 sensitive genes, 37 genes have human homologous analogs. Our results may provide a meaningful reference for understanding the action mode, cellular detoxification, and molecular regulation mechanisms of mercury toxicity. Full article

(This article belongs to the Special Issue Stress Research in Filamentous Fungi and Yeasts)

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23 pages, 4911 KiB

Open AccessArticle

Aspergillus nidulans gfdB, Encoding the Hyperosmotic Stress Protein Glycerol-3-phosphate Dehydrogenase, Disrupts Osmoadaptation in Aspergillus wentii

by Veronika Bodnár, Károly Antal, Ronald P. de Vries, István Pócsi and Tamás Emri

J. Fungi 2024, 10(4), 291; https://doi.org/10.3390/jof10040291 - 16 Apr 2024

Cited by 1 | Viewed by 1393

Abstract

The genome of the osmophilic Aspergillus wentii, unlike that of the osmotolerant Aspergillus nidulans, contains only the gfdA, but not the gfdB, glycerol 3-phosphate dehydrogenase gene. Here, we studied transcriptomic changes of A. nidulans (reference strain and ΔgfdB [...] Read more.

The genome of the osmophilic Aspergillus wentii, unlike that of the osmotolerant Aspergillus nidulans, contains only the gfdA, but not the gfdB, glycerol 3-phosphate dehydrogenase gene. Here, we studied transcriptomic changes of A. nidulans (reference strain and ΔgfdB gene deletion mutant) and A. wentii (reference strain and An-gfdB expressing mutant) elicited by high osmolarity. A. nidulans showed a canonic hyperosmotic stress response characterized by the upregulation of the trehalose and glycerol metabolism genes (including gfdB), as well as the genes of the high-osmolarity glycerol (HOG) map kinase pathway. The deletion of gfdB caused only negligible alterations in the transcriptome, suggesting that the glycerol metabolism was flexible enough to compensate for the missing GfdB activity in this species. A. wentii responded differently to increased osmolarity than did A. nidulans, e.g., the bulk upregulation of the glycerol and trehalose metabolism genes, along with the HOG pathway genes, was not detected. The expression of An-gfdB in A. wentii did not abolish osmophily, but it reduced growth and caused much bigger alterations in the transcriptome than did the missing gfdB gene in A. nidulans. Flexible glycerol metabolism and hence, two differently regulated gfd genes, may be more beneficial for osmotolerant (living under changing osmolarity) than for osmophilic (living under constantly high osmolarity) species. Full article

(This article belongs to the Special Issue Stress Research in Filamentous Fungi and Yeasts)

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18 pages, 3169 KiB

Open AccessArticle

The Oxidative Stress Response Highly Depends on Glucose and Iron Availability in Aspergillus fumigatus

by Tamás Emri, Károly Antal, Kinga Varga, Barnabás Csaba Gila and István Pócsi

J. Fungi 2024, 10(3), 221; https://doi.org/10.3390/jof10030221 - 18 Mar 2024

Cited by 2 | Viewed by 1625

Abstract

Pathogens have to cope with oxidative, iron- and carbon(glucose)-limitation stresses in the human body. To understand how combined iron–carbon limitation alters oxidative stress responses, Aspergillus fumigatus was cultured in glucose–peptone or peptone containing media supplemented or not with deferiprone as an iron chelator. [...] Read more.

Pathogens have to cope with oxidative, iron- and carbon(glucose)-limitation stresses in the human body. To understand how combined iron–carbon limitation alters oxidative stress responses, Aspergillus fumigatus was cultured in glucose–peptone or peptone containing media supplemented or not with deferiprone as an iron chelator. Changes in the transcriptome in these cultures were recorded after H₂O₂ treatment. Responses to oxidative stress were highly dependent on the availability of glucose and iron. Out of the 16 stress responsive antioxidative enzyme genes, only the cat2 catalase–peroxidase gene was upregulated in more than two culturing conditions. The transcriptional responses observed in iron metabolism also varied substantially in these cultures. Only extracellular siderophore production appeared important regardless of culturing conditions in oxidative stress protection, while the enhanced synthesis of Fe-S cluster proteins seemed to be crucial for oxidative stress treated iron-limited and fast growing (glucose rich) cultures. Although pathogens and host cells live together in the same place, their culturing conditions (e.g., iron availability or occurrence of oxidative stress) can be different. Therefore, inhibition of a universally important biochemical process, like Fe-S cluster assembly, may selectively inhibit the pathogen growth in vivo and represent a potential target for antifungal therapy. Full article

(This article belongs to the Special Issue Stress Research in Filamentous Fungi and Yeasts)

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16 pages, 2367 KiB

Open AccessArticle

An Evolved Strain of the Oleaginous Yeast Rhodotorula toruloides, Multi-Tolerant to the Major Inhibitors Present in Lignocellulosic Hydrolysates, Exhibits an Altered Cell Envelope

by Mónica A. Fernandes, Marta N. Mota, Nuno T. Faria and Isabel Sá-Correia

J. Fungi 2023, 9(11), 1073; https://doi.org/10.3390/jof9111073 - 2 Nov 2023

Cited by 5 | Viewed by 1995

Abstract

The presence of toxic compounds in lignocellulosic hydrolysates (LCH) is among the main barriers affecting the efficiency of lignocellulose-based fermentation processes, in particular, to produce biofuels, hindering the production of intracellular lipids by oleaginous yeasts. These microbial oils are promising sustainable alternatives to [...] Read more.

The presence of toxic compounds in lignocellulosic hydrolysates (LCH) is among the main barriers affecting the efficiency of lignocellulose-based fermentation processes, in particular, to produce biofuels, hindering the production of intracellular lipids by oleaginous yeasts. These microbial oils are promising sustainable alternatives to vegetable oils for biodiesel production. In this study, we explored adaptive laboratory evolution (ALE), under methanol- and high glycerol concentration-induced selective pressures, to improve the robustness of a Rhodotorula toruloides strain, previously selected to produce lipids from sugar beet hydrolysates by completely using the major C (carbon) sources present. An evolved strain, multi-tolerant not only to methanol but to four major inhibitors present in LCH (acetic acid, formic acid, hydroxymethylfurfural, and furfural) was isolated and the mechanisms underlying such multi-tolerance were examined, at the cellular envelope level. Results indicate that the evolved multi-tolerant strain has a cell wall that is less susceptible to zymolyase and a decreased permeability, based on the propidium iodide fluorescent probe, in the absence or presence of those inhibitors. The improved performance of this multi-tolerant strain for lipid production from a synthetic lignocellulosic hydrolysate medium, supplemented with those inhibitors, was confirmed. Full article

(This article belongs to the Special Issue Stress Research in Filamentous Fungi and Yeasts)

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15 pages, 3223 KiB

Open AccessArticle

Global Transcriptomic Changes Elicited by sodB Deletion and Menadione Exposure in Aspergillus nidulans

by Klaudia Pákozdi, Tamás Emri, Károly Antal and István Pócsi

J. Fungi 2023, 9(11), 1060; https://doi.org/10.3390/jof9111060 - 30 Oct 2023

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Abstract

Manganese superoxide dismutases (MnSODs) play a pivotal role in the preservation of mitochondrial integrity and function in fungi under various endogenous and exogenous stresses. Deletion of Aspergillus nidulans mnSOD/SodB increased oxidative stress sensitivity and apoptotic cell death rates as well as affected antioxidant [...] Read more.

Manganese superoxide dismutases (MnSODs) play a pivotal role in the preservation of mitochondrial integrity and function in fungi under various endogenous and exogenous stresses. Deletion of Aspergillus nidulans mnSOD/SodB increased oxidative stress sensitivity and apoptotic cell death rates as well as affected antioxidant enzyme and sterigmatocystin productions, respiration, conidiation and the stress tolerance of conidiospores. The physiological consequences of the lack of sodB were more pronounced during carbon starvation than in the presence of glucose. Lack of SodB also affected the changes in the transcriptome, recorded by high-throughput RNA sequencing, in menadione sodium bisulfite (MSB)-exposed, submerged cultures supplemented with glucose. Surprisingly, the difference between the global transcriptional changes of the ΔsodB mutant and the control strain were relatively small, indicating that the SodB-dependent maintenance of mitochondrial integrity was not essential under these experimental conditions. Owing to the outstanding physiological flexibility of the Aspergilli, certain antioxidant enzymes and endogenous antioxidants together with the reduction in mitochondrial functions compensated well for the lack of SodB. The lack of sodB reduced the growth of surface cultures more than of the submerged culture, which should be considered in future development of fungal disinfection methods. Full article

(This article belongs to the Special Issue Stress Research in Filamentous Fungi and Yeasts)

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