Dataset Information

Expansion of the TLO gene family enhances the virulence of Candida species.

ABSTRACT: The TLO genes are a family of subtelomeric ORFs in the fungal pathogens Candida albicans and C. dubliniensis encoding a subunit of the Mediator complex homologous to Med2. The more virulent pathogen C. albicans has 15 copies of the gene whereas the less pathogenic species C. dubliniensis has only two. To investigate if expansion of the TLO repertoire in C. dubliniensis has an effect on phenotype and virulence we expressed three representative C. albicans TLO genes (TLO?2, TLO?11 and TLO?12) in a wild type C. dubliniensis background, under the control of either their native or the ACT1 promoter. Expression of TLO?2 resulted in a hyperfilamentous phenotype, while overexpression of TLO?11 and TLO?12 resulted in enhanced resistance to oxidative stress. Expression of all three TLO genes from the ACT1 promoter resulted in increased virulence in the Galleria infection model. In order to further investigate if individual TLO genes exhibit differences in function we expressed six representative C. albicans TLO genes in a C. dubliniensis ?tlo1/?tlo2 double mutant. Differences were observed in the ability of the expressed CaTLOs to complement the various phenotypes of the mutant. All TLO genes with the exception of TLO?7 could restore filamentation, however only TLO?9, ?11 and ?12 could restore chlamydospore formation. Differences in the ability of CaTLO genes to restore growth in the presence of H2O2, calcofluor white, Congo red and at 42°C were observed. Only TLO?3 restored wild-type levels of virulence in the Galleria infection model. These data show that expansion of the TLO gene family in C. dubliniensis results in gain of function and that there is functional diversity amongst members of the gene family. We propose that this expansion of the TLO family contributes to the success of C. albicans as a commensal and opportunistic pathogen.

SUBMITTER: Flanagan PR

PROVIDER: S-EPMC6054389 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Expansion of the TLO gene family enhances the virulence of Candida species.

Flanagan Peter R PR Fletcher Jessica J Boyle Hannah H Sulea Razvan R Moran Gary P GP Sullivan Derek J DJ

PloS one 20180720 7

The TLO genes are a family of subtelomeric ORFs in the fungal pathogens Candida albicans and C. dubliniensis encoding a subunit of the Mediator complex homologous to Med2. The more virulent pathogen C. albicans has 15 copies of the gene whereas the less pathogenic species C. dubliniensis has only two. To investigate if expansion of the TLO repertoire in C. dubliniensis has an effect on phenotype and virulence we expressed three representative C. albicans TLO genes (TLOβ2, TLOγ11 and TLOα12) in a ...[more]

PMID: 30028853

Similar Datasets

Project description:Gene duplication facilitates functional diversification and provides greater phenotypic flexibility to an organism. Expanded gene families arise through repeated gene duplication but the extent of functional divergence that accompanies each paralogous gene is generally unexplored because of the difficulty in isolating the effects of single family members. The telomere-associated (TLO) gene family is a remarkable example of gene family expansion, with 14 members in the more pathogenic Candida albicans relative to two TLO genes in the closely-related species C. dubliniensis. TLO genes encode interchangeable Med2 subunits of the major transcriptional regulatory complex Mediator. To identify biological functions associated with each C. albicans TLO, expression of individual family members was regulated using a Tet-ON system and the strains were assessed across a range of phenotypes involved in growth and virulence traits. All TLOs affected multiple phenotypes and a single phenotype was often affected by multiple TLOs, including simple phenotypes such as cell aggregation and complex phenotypes such as virulence in a Galleria mellonella model of infection. No phenotype was regulated by all TLOs, suggesting neofunctionalization or subfunctionalization of ancestral properties among different family members. Importantly, regulation of three phenotypes could be mapped to individual polymorphic sites among the TLO genes, including an indel correlated with two phenotypes, growth in sucrose and macrophage killing. Different selective pressures have operated on the TLO sequence, with the 5' conserved Med2 domain experiencing purifying selection and the gene/clade-specific 3' end undergoing extensive positive selection that may contribute to the impact of individual TLOs on phenotypic variability. Therefore, expansion of the TLO gene family has conferred unique regulatory properties to each paralog such that it influences a range of phenotypes. We posit that the genetic diversity associated with this expansion contributed to C. albicans success as a commensal and opportunistic pathogen.

Project description:Filamentous growth is a hallmark of C. albicans pathogenicity compared to less-virulent ascomycetes. A multitude of transcription factors regulate filamentous growth in response to specific environmental cues. Our work, however, suggests the evolutionary history of C. albicans that resulted in its filamentous growth plasticity may be tied to a change in the general transcription machinery rather than transcription factors and their specific targets. A key genomic difference between C. albicans and its less-virulent relatives, including its closest relative C. dubliniensis, is the unique expansion of the TLO (TeLOmere-associated) gene family in C. albicans. Individual Tlo proteins are fungal-specific subunits of Mediator, a large multi-subunit eukaryotic transcriptional co-activator complex. This amplification results in a large pool of 'free,' non-Mediator associated, Tlo protein present in C. albicans, but not in C. dubliniensis or other ascomycetes with attenuated virulence. We show that engineering a large 'free' pool of the C. dubliniensis Tlo2 (CdTlo2) protein in C. dubliniensis, through overexpression, results in a number of filamentation phenotypes typically associated only with C. albicans. The amplitude of these phenotypes is proportional to the amount of overexpressed CdTlo2 protein. Overexpression of other C. dubliniensis and C. albicans Tlo proteins do result in these phenotypes. Tlo proteins and their orthologs contain a Mediator interaction domain, and a potent transcriptional activation domain. Nuclear localization of the CdTlo2 activation domain, facilitated naturally by the Tlo Mediator binding domain or artificially through an appended nuclear localization signal, is sufficient for the CdTlo2 overexpression phenotypes. A C. albicans med3 null mutant causes multiple defects including the inability to localize Tlo proteins to the nucleus and reduced virulence in a murine systemic infection model. Our data supports a model in which the activation domain of 'free' Tlo protein competes with DNA bound transcription factors for targets that regulate key aspects of C. albicans cell physiology.

Project description:Systemic infections of Candida species pose a significant threat to public health. Toxicity associated with current therapies and emergence of resistant strains present major therapeutic challenges. Here, we report exploitation of the probiotic properties of two novel, food-derived yeasts, Saccharomyces cerevisiae (strain KTP) and Issatchenkia occidentalis (strain ApC), as an alternative approach to combat widespread opportunistic fungal infections. Both yeasts inhibit virulence traits such as adhesion, filamentation, and biofilm formation of several non-albicans Candida species, including Candida tropicalis, Candida krusei, Candida glabrata, and Candida parapsilosis as well as the recently identified multidrug-resistant species Candida auris They inhibit adhesion to abiotic surfaces as well as cultured colon epithelial cells. Furthermore, probiotic treatment blocks the formation of biofilms of individual non-albicans Candida strains as well as mixed-culture biofilms of each non-albicans Candida strain in combination with Candida albicans The probiotic yeasts attenuated non-albicans Candida infections in a live animal. In vivo studies using Caenorhabditis elegans suggest that exposure to probiotic yeasts protects nematodes from infection with non-albicans Candida strains compared to worms that were not exposed to the probiotic yeasts. Furthermore, application of probiotic yeasts postinfection with non-albicans Candida alleviated pathogenic colonization of the nematode gut. The probiotic properties of these novel yeasts are better than or comparable to those of the commercially available probiotic yeast Saccharomyces boulardii, which was used as a reference strain throughout this study. These results indicate that yeasts derived from food sources could serve as an effective alternative to antifungal therapy against emerging pathogenic Candida species.IMPORTANCE Non-albicans Candida-associated infections have emerged as a major risk factor in the hospitalized and immunecompromised patients. Besides, antifungal-associated complications occur more frequently with these non-albicans Candida species than with C. albicans Therefore, as an alternative approach to combat these widespread non-albicans Candida-associated infections, here we showed the probiotic effect of two yeasts, Saccharomyces cerevisiae (strain KTP) and Issatchenkia occidentalis (ApC), in preventing adhesion and biofilm formation of five non-albicans Candida strains, Candida tropicalis, Candida krusei, Candida glabrata, Candida parapsilosis, and Candida auris The result would influence the current trend of the conversion of conventional antimicrobial therapy into beneficial probiotic microbe-associated antimicrobial treatment.

Project description:BackgroundThe Bacillus cereus sensu lato group consists of six species (B. anthracis, B. cereus, B. mycoides, B. pseudomycoides, B. thuringiensis, and B. weihenstephanensis). While classical microbial taxonomy proposed these organisms as distinct species, newer molecular phylogenies and comparative genome sequencing suggests that these organisms should be classified as a single species (thus, we will refer to these organisms collectively as the Bc species-group). How do we account for the underlying similarity of these phenotypically diverse microbes? It has been established for some time that the most rapidly evolving and evolutionarily flexible portions of the bacterial genome are regulatory sequences and transcriptional networks. Other studies have suggested that the sigma factor gene family of these organisms has diverged and expanded significantly relative to their ancestors; sigma factors are those portions of the bacterial transcriptional apparatus that control RNA polymerase recognition for promoter selection. Thus, examining sigma factor divergence in these organisms would concurrently examine both regulatory sequences and transcriptional networks important for divergence. We began this examination by comparison to the sigma factor gene set of B. subtilis.ResultsPhylogenetic analysis of the Bc species-group utilizing 157 single-copy genes of the family Bacillaceae suggests that several taxonomic revisions of the genus Bacillus should be considered. Within the Bc species-group there is little indication that the currently recognized species form related sub-groupings, suggesting that they are members of the same species. The sigma factor gene family encoded by the Bc species-group appears to be the result of a dynamic gene-duplication and gene-loss process that in previous analyses underestimated the true heterogeneity of the sigma factor content in the Bc species-group.ConclusionsExpansion of the sigma factor gene family appears to have preferentially occurred within the extracytoplasmic function (ECF) sigma factor genes, while the primary alternative (PA) sigma factor genes are, in general, highly conserved with those found in B. subtilis. Divergence of the sigma-controlled transcriptional regulons among various members of the Bc species-group likely has a major role in explaining the diversity of phenotypic characteristics seen in members of the Bc species-group.

Dataset Information

Expansion of the TLO gene family enhances the virulence of Candida species.

Publications

Expansion of the TLO gene family enhances the virulence of Candida species.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets