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Fungal Morphology, Iron Homeostasis, and Lipid Metabolism Regulated by a GATA Transcription Factor in Blastomyces dermatitidis.

Marty AJ, Broman AT, Zarnowski R, Dwyer TG, Bond LM, Lounes-Hadj Sahraoui A, Fontaine J, Ntambi JM, Keleş S, Kendziorski C, Gauthier GM - PLoS Pathog. (2015)

Bottom Line: This included genes involved with siderophore biosynthesis and uptake, iron homeostasis, and genes unrelated to iron assimilation.Chromatin immunoprecipitation, RNA interference, and overexpression analyses suggested that SREB was in a negative regulatory circuit with the bZIP transcription factor encoded by HAPX.Both SREB and HAPX affected morphogenesis at 22°C; however, large changes in transcript abundance by gene deletion for SREB or strong overexpression for HAPX were required to alter the phase transition.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Wisconsin, Madison, Madison, Wisconsin, United States of America.

ABSTRACT
In response to temperature, Blastomyces dermatitidis converts between yeast and mold forms. Knowledge of the mechanism(s) underlying this response to temperature remains limited. In B. dermatitidis, we identified a GATA transcription factor, SREB, important for the transition to mold. Null mutants (SREBΔ) fail to fully complete the conversion to mold and cannot properly regulate siderophore biosynthesis. To capture the transcriptional response regulated by SREB early in the phase transition (0-48 hours), gene expression microarrays were used to compare SREB∆ to an isogenic wild type isolate. Analysis of the time course microarray data demonstrated SREB functioned as a transcriptional regulator at 37°C and 22°C. Bioinformatic and biochemical analyses indicated SREB was involved in diverse biological processes including iron homeostasis, biosynthesis of triacylglycerol and ergosterol, and lipid droplet formation. Integration of microarray data, bioinformatics, and chromatin immunoprecipitation identified a subset of genes directly bound and regulated by SREB in vivo in yeast (37°C) and during the phase transition to mold (22°C). This included genes involved with siderophore biosynthesis and uptake, iron homeostasis, and genes unrelated to iron assimilation. Functional analysis suggested that lipid droplets were actively metabolized during the phase transition and lipid metabolism may contribute to filamentous growth at 22°C. Chromatin immunoprecipitation, RNA interference, and overexpression analyses suggested that SREB was in a negative regulatory circuit with the bZIP transcription factor encoded by HAPX. Both SREB and HAPX affected morphogenesis at 22°C; however, large changes in transcript abundance by gene deletion for SREB or strong overexpression for HAPX were required to alter the phase transition.

No MeSH data available.


Related in: MedlinePlus

Weighted gene co-expression network analysis (WGCNA).WGCNA identified 30 color-coded modules including 4 modules in which the majority of genes were differentially expressed and enriched for GO terms. (A) Midnight blue, (B) green-yellow, (C) blue, and (D) turquoise modules were enriched metabolic process, fatty acid biosynthesis / catalytic activity, transmembrane transport, and transcription factor activity GO terms, respectively. Putative gene function was assigned by integrating GO term, tBLASTn, and pFAM analyses. Fluorescent intensity values from microarray analysis for heat maps were clustered using Euclidean distance with average linkage. Heat map analysis demonstrated distinct transcriptional patterns between SREB∆ and WT for each module across the time course: (A) midnight blue–failure of transcript for genes in SREB∆ to increase; (B) green yellow–decrease in transcript for genes in SREB∆; (C) blue–increase in transcription was attenuated for genes in SREB∆; and (D) turquoise–increased transcription for genes in SREB∆. Genes for the heat maps are in Supplemental Table 5.
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ppat.1004959.g002: Weighted gene co-expression network analysis (WGCNA).WGCNA identified 30 color-coded modules including 4 modules in which the majority of genes were differentially expressed and enriched for GO terms. (A) Midnight blue, (B) green-yellow, (C) blue, and (D) turquoise modules were enriched metabolic process, fatty acid biosynthesis / catalytic activity, transmembrane transport, and transcription factor activity GO terms, respectively. Putative gene function was assigned by integrating GO term, tBLASTn, and pFAM analyses. Fluorescent intensity values from microarray analysis for heat maps were clustered using Euclidean distance with average linkage. Heat map analysis demonstrated distinct transcriptional patterns between SREB∆ and WT for each module across the time course: (A) midnight blue–failure of transcript for genes in SREB∆ to increase; (B) green yellow–decrease in transcript for genes in SREB∆; (C) blue–increase in transcription was attenuated for genes in SREB∆; and (D) turquoise–increased transcription for genes in SREB∆. Genes for the heat maps are in Supplemental Table 5.

Mentions: WGCNA was performed to identify groups of co-expressed genes. All genes across all time points were included in the analysis. We identified 30 color-coded modules including 11 modules that were enriched for GO terms (Table 3). In 4 of these 11 modules, the majority of genes were differentially expressed (53.5%– 85.0%; Table 3). Moreover, 3 modules were enriched for GO terms previously identified including metabolic process (midnight blue module), fatty acid biosynthesis / catalytic activity (green-yellow module), and transmembrane transport (blue module) (Tables 2 and 3and Fig 2A–2C). Although these modules were enriched for specific GO terms, the predicted functions for DE genes within each module was diverse. Moreover, a substantial number of DE genes in each module had unknown function (Fig 2A–2D). In the midnight blue module, transcription of DE genes in SREB∆ was lower at baseline (37°C) and failed to properly increase across the 22°C time points when compared to WT (Fig 2A and S5 Table). In contrast, DE genes in SREB∆ exhibited a more precipitous decrease in transcription across the time course than WT in the green-yellow module (Fig 2B and S5 Table). For the blue module, the increase in transcription across the time points at 22°C was blunted for DE genes in SREB∆ versus WT (Fig 2C and S5 Table). Transcription of DE genes in SREB∆ in the turquoise module increased during the time course compared to WT (Fig 2D and S5 Table), which suggested these genes were derepressed. Collectively, this analysis indicated that deletion of SREB resulted in specific transcriptional changes at 37°C and 22°C.


Fungal Morphology, Iron Homeostasis, and Lipid Metabolism Regulated by a GATA Transcription Factor in Blastomyces dermatitidis.

Marty AJ, Broman AT, Zarnowski R, Dwyer TG, Bond LM, Lounes-Hadj Sahraoui A, Fontaine J, Ntambi JM, Keleş S, Kendziorski C, Gauthier GM - PLoS Pathog. (2015)

Weighted gene co-expression network analysis (WGCNA).WGCNA identified 30 color-coded modules including 4 modules in which the majority of genes were differentially expressed and enriched for GO terms. (A) Midnight blue, (B) green-yellow, (C) blue, and (D) turquoise modules were enriched metabolic process, fatty acid biosynthesis / catalytic activity, transmembrane transport, and transcription factor activity GO terms, respectively. Putative gene function was assigned by integrating GO term, tBLASTn, and pFAM analyses. Fluorescent intensity values from microarray analysis for heat maps were clustered using Euclidean distance with average linkage. Heat map analysis demonstrated distinct transcriptional patterns between SREB∆ and WT for each module across the time course: (A) midnight blue–failure of transcript for genes in SREB∆ to increase; (B) green yellow–decrease in transcript for genes in SREB∆; (C) blue–increase in transcription was attenuated for genes in SREB∆; and (D) turquoise–increased transcription for genes in SREB∆. Genes for the heat maps are in Supplemental Table 5.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4482641&req=5

ppat.1004959.g002: Weighted gene co-expression network analysis (WGCNA).WGCNA identified 30 color-coded modules including 4 modules in which the majority of genes were differentially expressed and enriched for GO terms. (A) Midnight blue, (B) green-yellow, (C) blue, and (D) turquoise modules were enriched metabolic process, fatty acid biosynthesis / catalytic activity, transmembrane transport, and transcription factor activity GO terms, respectively. Putative gene function was assigned by integrating GO term, tBLASTn, and pFAM analyses. Fluorescent intensity values from microarray analysis for heat maps were clustered using Euclidean distance with average linkage. Heat map analysis demonstrated distinct transcriptional patterns between SREB∆ and WT for each module across the time course: (A) midnight blue–failure of transcript for genes in SREB∆ to increase; (B) green yellow–decrease in transcript for genes in SREB∆; (C) blue–increase in transcription was attenuated for genes in SREB∆; and (D) turquoise–increased transcription for genes in SREB∆. Genes for the heat maps are in Supplemental Table 5.
Mentions: WGCNA was performed to identify groups of co-expressed genes. All genes across all time points were included in the analysis. We identified 30 color-coded modules including 11 modules that were enriched for GO terms (Table 3). In 4 of these 11 modules, the majority of genes were differentially expressed (53.5%– 85.0%; Table 3). Moreover, 3 modules were enriched for GO terms previously identified including metabolic process (midnight blue module), fatty acid biosynthesis / catalytic activity (green-yellow module), and transmembrane transport (blue module) (Tables 2 and 3and Fig 2A–2C). Although these modules were enriched for specific GO terms, the predicted functions for DE genes within each module was diverse. Moreover, a substantial number of DE genes in each module had unknown function (Fig 2A–2D). In the midnight blue module, transcription of DE genes in SREB∆ was lower at baseline (37°C) and failed to properly increase across the 22°C time points when compared to WT (Fig 2A and S5 Table). In contrast, DE genes in SREB∆ exhibited a more precipitous decrease in transcription across the time course than WT in the green-yellow module (Fig 2B and S5 Table). For the blue module, the increase in transcription across the time points at 22°C was blunted for DE genes in SREB∆ versus WT (Fig 2C and S5 Table). Transcription of DE genes in SREB∆ in the turquoise module increased during the time course compared to WT (Fig 2D and S5 Table), which suggested these genes were derepressed. Collectively, this analysis indicated that deletion of SREB resulted in specific transcriptional changes at 37°C and 22°C.

Bottom Line: This included genes involved with siderophore biosynthesis and uptake, iron homeostasis, and genes unrelated to iron assimilation.Chromatin immunoprecipitation, RNA interference, and overexpression analyses suggested that SREB was in a negative regulatory circuit with the bZIP transcription factor encoded by HAPX.Both SREB and HAPX affected morphogenesis at 22°C; however, large changes in transcript abundance by gene deletion for SREB or strong overexpression for HAPX were required to alter the phase transition.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Wisconsin, Madison, Madison, Wisconsin, United States of America.

ABSTRACT
In response to temperature, Blastomyces dermatitidis converts between yeast and mold forms. Knowledge of the mechanism(s) underlying this response to temperature remains limited. In B. dermatitidis, we identified a GATA transcription factor, SREB, important for the transition to mold. Null mutants (SREBΔ) fail to fully complete the conversion to mold and cannot properly regulate siderophore biosynthesis. To capture the transcriptional response regulated by SREB early in the phase transition (0-48 hours), gene expression microarrays were used to compare SREB∆ to an isogenic wild type isolate. Analysis of the time course microarray data demonstrated SREB functioned as a transcriptional regulator at 37°C and 22°C. Bioinformatic and biochemical analyses indicated SREB was involved in diverse biological processes including iron homeostasis, biosynthesis of triacylglycerol and ergosterol, and lipid droplet formation. Integration of microarray data, bioinformatics, and chromatin immunoprecipitation identified a subset of genes directly bound and regulated by SREB in vivo in yeast (37°C) and during the phase transition to mold (22°C). This included genes involved with siderophore biosynthesis and uptake, iron homeostasis, and genes unrelated to iron assimilation. Functional analysis suggested that lipid droplets were actively metabolized during the phase transition and lipid metabolism may contribute to filamentous growth at 22°C. Chromatin immunoprecipitation, RNA interference, and overexpression analyses suggested that SREB was in a negative regulatory circuit with the bZIP transcription factor encoded by HAPX. Both SREB and HAPX affected morphogenesis at 22°C; however, large changes in transcript abundance by gene deletion for SREB or strong overexpression for HAPX were required to alter the phase transition.

No MeSH data available.


Related in: MedlinePlus