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The MAP kinase HwHog1 from the halophilic black yeast Hortaea werneckii: coping with stresses in solar salterns.

Lenassi M, Vaupotic T, Gunde-Cimerman N, Plemenitas A - Saline Syst. (2007)

Bottom Line: Identification of HOG1-like genes from other halotolerant fungi isolated from solar salterns demonstrates a high degree of similarity and excellent phylogenetic clustering with orthologues of fungal origin.The HOG signalling pathway has an important role in sensing and responding to hyper-osmolar, oxidative and high-temperature stresses in the halophilic fungi H. werneckii.These findings are an important advance in our understanding of the HOG pathway response to stress in H. werneckii, a proposed model organism for studying the salt tolerance of halophilic and halotolerant eukaryotes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Vrazov trg 2, Ljubljana, Slovenia. metka.lenassi@mf.uni-lj.si

ABSTRACT

Background: Hortaea werneckii is one of the most salt-tolerant species among microorganisms. It has been isolated from hypersaline waters of salterns as one of the predominant species of a group of halophilic and halotolerant melanized yeast-like fungi, arbitrarily named as "black yeasts". It has previously been shown that H. werneckii has distinct mechanisms of adaptation to high salinity environments that are not seen in salt-sensitive and only moderately salt-tolerant fungi. In H. werneckii, the HOG pathway is important for sensing the changes in environmental osmolarity, as demonstrated by identification of three main pathway components: the mitogen-activated protein kinase (MAPK) HwHog1, the MAPK kinase HwPbs2, and the putative histidine kinase osmosensor HwHhk7.

Results: In this study, we show that the expression of HwHOG1 in salt-adapted cells depends on the environmental salinity and that HwHOG1 transcription responds rapidly but reciprocally to the acute hyper-saline or hypo-saline stress. Molecular modelling of HwHog1 reveals an overall structural homology with other MAPKs. HwHog1 complements the function of ScHog1 in the Saccharomyces cerevisiae multistress response. We also show that hyper-osmolar, oxidative and high-temperature stresses activate the HwHog1 kinase, although under high-temperature stress the signal is not transmitted via the MAPK kinase Pbs2. Identification of HOG1-like genes from other halotolerant fungi isolated from solar salterns demonstrates a high degree of similarity and excellent phylogenetic clustering with orthologues of fungal origin.

Conclusion: The HOG signalling pathway has an important role in sensing and responding to hyper-osmolar, oxidative and high-temperature stresses in the halophilic fungi H. werneckii. These findings are an important advance in our understanding of the HOG pathway response to stress in H. werneckii, a proposed model organism for studying the salt tolerance of halophilic and halotolerant eukaryotes.

No MeSH data available.


Related in: MedlinePlus

Phylogenetic tree of deduced Hog1-like MAPKs in the halotolerant fungi and other fungal representatives. The phylogenetic tree was constructed with the neighbour-joining method [36] based on the amino-acid sequences, using the MEGA 3.1 programme [37], and arbitrarily rooted with W. ichthyophaga. The numbers at the nodes are bootstrap confidence values based on 1,000 replicas. The phylogenetic tree was subjected to a Poisson correction. The saltern-inhabiting halotolerant fungi are indicated by the grey boxes.
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Figure 5: Phylogenetic tree of deduced Hog1-like MAPKs in the halotolerant fungi and other fungal representatives. The phylogenetic tree was constructed with the neighbour-joining method [36] based on the amino-acid sequences, using the MEGA 3.1 programme [37], and arbitrarily rooted with W. ichthyophaga. The numbers at the nodes are bootstrap confidence values based on 1,000 replicas. The phylogenetic tree was subjected to a Poisson correction. The saltern-inhabiting halotolerant fungi are indicated by the grey boxes.

Mentions: A functional phylogenetic tree based on the amino-acid alignment of the Hog1 sequences from the above-mentioned fungi was generated using the neighbour-joining method implemented in ClustalW (Fig. 5). According to the amino-acid sequences, the fungi isolated from solar salterns are grouped into two clusters. The first is represented by halotolerant-to-extremely-halotolerant black yeasts of the order Dothideales. The second cluster is composed of the genus Wallemia, with the halophilic W. ichthyophaga being distinct from the more xerophilic W. muriae and W. sebi. As expected, S. cerevisiae, C. albicans and D. hansenii were grouped together in the Saccharomycetales cluster.


The MAP kinase HwHog1 from the halophilic black yeast Hortaea werneckii: coping with stresses in solar salterns.

Lenassi M, Vaupotic T, Gunde-Cimerman N, Plemenitas A - Saline Syst. (2007)

Phylogenetic tree of deduced Hog1-like MAPKs in the halotolerant fungi and other fungal representatives. The phylogenetic tree was constructed with the neighbour-joining method [36] based on the amino-acid sequences, using the MEGA 3.1 programme [37], and arbitrarily rooted with W. ichthyophaga. The numbers at the nodes are bootstrap confidence values based on 1,000 replicas. The phylogenetic tree was subjected to a Poisson correction. The saltern-inhabiting halotolerant fungi are indicated by the grey boxes.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1828057&req=5

Figure 5: Phylogenetic tree of deduced Hog1-like MAPKs in the halotolerant fungi and other fungal representatives. The phylogenetic tree was constructed with the neighbour-joining method [36] based on the amino-acid sequences, using the MEGA 3.1 programme [37], and arbitrarily rooted with W. ichthyophaga. The numbers at the nodes are bootstrap confidence values based on 1,000 replicas. The phylogenetic tree was subjected to a Poisson correction. The saltern-inhabiting halotolerant fungi are indicated by the grey boxes.
Mentions: A functional phylogenetic tree based on the amino-acid alignment of the Hog1 sequences from the above-mentioned fungi was generated using the neighbour-joining method implemented in ClustalW (Fig. 5). According to the amino-acid sequences, the fungi isolated from solar salterns are grouped into two clusters. The first is represented by halotolerant-to-extremely-halotolerant black yeasts of the order Dothideales. The second cluster is composed of the genus Wallemia, with the halophilic W. ichthyophaga being distinct from the more xerophilic W. muriae and W. sebi. As expected, S. cerevisiae, C. albicans and D. hansenii were grouped together in the Saccharomycetales cluster.

Bottom Line: Identification of HOG1-like genes from other halotolerant fungi isolated from solar salterns demonstrates a high degree of similarity and excellent phylogenetic clustering with orthologues of fungal origin.The HOG signalling pathway has an important role in sensing and responding to hyper-osmolar, oxidative and high-temperature stresses in the halophilic fungi H. werneckii.These findings are an important advance in our understanding of the HOG pathway response to stress in H. werneckii, a proposed model organism for studying the salt tolerance of halophilic and halotolerant eukaryotes.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Vrazov trg 2, Ljubljana, Slovenia. metka.lenassi@mf.uni-lj.si

ABSTRACT

Background: Hortaea werneckii is one of the most salt-tolerant species among microorganisms. It has been isolated from hypersaline waters of salterns as one of the predominant species of a group of halophilic and halotolerant melanized yeast-like fungi, arbitrarily named as "black yeasts". It has previously been shown that H. werneckii has distinct mechanisms of adaptation to high salinity environments that are not seen in salt-sensitive and only moderately salt-tolerant fungi. In H. werneckii, the HOG pathway is important for sensing the changes in environmental osmolarity, as demonstrated by identification of three main pathway components: the mitogen-activated protein kinase (MAPK) HwHog1, the MAPK kinase HwPbs2, and the putative histidine kinase osmosensor HwHhk7.

Results: In this study, we show that the expression of HwHOG1 in salt-adapted cells depends on the environmental salinity and that HwHOG1 transcription responds rapidly but reciprocally to the acute hyper-saline or hypo-saline stress. Molecular modelling of HwHog1 reveals an overall structural homology with other MAPKs. HwHog1 complements the function of ScHog1 in the Saccharomyces cerevisiae multistress response. We also show that hyper-osmolar, oxidative and high-temperature stresses activate the HwHog1 kinase, although under high-temperature stress the signal is not transmitted via the MAPK kinase Pbs2. Identification of HOG1-like genes from other halotolerant fungi isolated from solar salterns demonstrates a high degree of similarity and excellent phylogenetic clustering with orthologues of fungal origin.

Conclusion: The HOG signalling pathway has an important role in sensing and responding to hyper-osmolar, oxidative and high-temperature stresses in the halophilic fungi H. werneckii. These findings are an important advance in our understanding of the HOG pathway response to stress in H. werneckii, a proposed model organism for studying the salt tolerance of halophilic and halotolerant eukaryotes.

No MeSH data available.


Related in: MedlinePlus