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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.


Cell morphology during the early stages following a drop in temperature.(A) Morphology of wild-type (WT) and SREB∆ at 37°C and at 6, 24, and 48-hrs after a drop in temperature at 22°C. When compared to WT, SREB∆ cells exhibited a delay in the filamentous growth (germ tube and hyphal formation). At 22°C, SREB∆ filaments were abnormal in morphology. Scale bar equals 10 μm. (B) Percentage of WT and SREB∆ cells with yeast morphology, germ tube development, and hyphal growth at 37°C and 22°C. Results were averaged from 2 independent experiments (> 200 cells counted in duplicate). (C) Percent of WT and SREB∆ cells that are viable at 37°C and 22°C. Results were averaged from 2 independent experiments (> 200 cells counted in duplicate)
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ppat.1004959.g001: Cell morphology during the early stages following a drop in temperature.(A) Morphology of wild-type (WT) and SREB∆ at 37°C and at 6, 24, and 48-hrs after a drop in temperature at 22°C. When compared to WT, SREB∆ cells exhibited a delay in the filamentous growth (germ tube and hyphal formation). At 22°C, SREB∆ filaments were abnormal in morphology. Scale bar equals 10 μm. (B) Percentage of WT and SREB∆ cells with yeast morphology, germ tube development, and hyphal growth at 37°C and 22°C. Results were averaged from 2 independent experiments (> 200 cells counted in duplicate). (C) Percent of WT and SREB∆ cells that are viable at 37°C and 22°C. Results were averaged from 2 independent experiments (> 200 cells counted in duplicate)

Mentions: To investigate the kinetics of the phase transition defect in SREB∆, we compared it to an isogenic wild-type (WT) control at 37°C and at 6, 24, and 48-hrs following a drop in temperature to 22°C (Fig 1A–1C). At 37°C, WT and SREB∆ grew as budding yeast (Fig 1A and 1B). After 6-hrs at 22°C, WT and SREB∆ continued to have a yeast morphology with 22% and 4% cells exhibiting early germ tube development, respectively (Fig 1A and 1B). At 24 and 48-hrs at 22°C, the germ tubes of WT cells had elongated to become hyphae (Fig 1A and 1B). In contrast, sharp morphologic differences between SREB∆ and WT became apparent at 24 and 48-hrs at 22°C with SREB∆ demonstrating a delay in germ tube formation and stunted, misshapen germ tubes and hyphae (Fig 1A and 1B). Deletion of SREB did not affect cell viability (Fig 1C).


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)

Cell morphology during the early stages following a drop in temperature.(A) Morphology of wild-type (WT) and SREB∆ at 37°C and at 6, 24, and 48-hrs after a drop in temperature at 22°C. When compared to WT, SREB∆ cells exhibited a delay in the filamentous growth (germ tube and hyphal formation). At 22°C, SREB∆ filaments were abnormal in morphology. Scale bar equals 10 μm. (B) Percentage of WT and SREB∆ cells with yeast morphology, germ tube development, and hyphal growth at 37°C and 22°C. Results were averaged from 2 independent experiments (> 200 cells counted in duplicate). (C) Percent of WT and SREB∆ cells that are viable at 37°C and 22°C. Results were averaged from 2 independent experiments (> 200 cells counted in duplicate)
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4482641&req=5

ppat.1004959.g001: Cell morphology during the early stages following a drop in temperature.(A) Morphology of wild-type (WT) and SREB∆ at 37°C and at 6, 24, and 48-hrs after a drop in temperature at 22°C. When compared to WT, SREB∆ cells exhibited a delay in the filamentous growth (germ tube and hyphal formation). At 22°C, SREB∆ filaments were abnormal in morphology. Scale bar equals 10 μm. (B) Percentage of WT and SREB∆ cells with yeast morphology, germ tube development, and hyphal growth at 37°C and 22°C. Results were averaged from 2 independent experiments (> 200 cells counted in duplicate). (C) Percent of WT and SREB∆ cells that are viable at 37°C and 22°C. Results were averaged from 2 independent experiments (> 200 cells counted in duplicate)
Mentions: To investigate the kinetics of the phase transition defect in SREB∆, we compared it to an isogenic wild-type (WT) control at 37°C and at 6, 24, and 48-hrs following a drop in temperature to 22°C (Fig 1A–1C). At 37°C, WT and SREB∆ grew as budding yeast (Fig 1A and 1B). After 6-hrs at 22°C, WT and SREB∆ continued to have a yeast morphology with 22% and 4% cells exhibiting early germ tube development, respectively (Fig 1A and 1B). At 24 and 48-hrs at 22°C, the germ tubes of WT cells had elongated to become hyphae (Fig 1A and 1B). In contrast, sharp morphologic differences between SREB∆ and WT became apparent at 24 and 48-hrs at 22°C with SREB∆ demonstrating a delay in germ tube formation and stunted, misshapen germ tubes and hyphae (Fig 1A and 1B). Deletion of SREB did not affect cell viability (Fig 1C).

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.