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Tuning Hsf1 levels drives distinct fungal morphogenetic programs with depletion impairing Hsp90 function and overexpression expanding the target space
Amanda O. Veri, 1 Zhengqiang Miao, 2 Rebecca S. Shapiro, 3 Faiza Tebbji, 4 Teresa R. O’Meara, 1 Sang Hu Kim, 1 Juan Colazo, 5 Kaeling Tan, 2 Valmik K. Vyas, 6 Malcolm Whiteway, 7 Nicole Robbins, 1 Koon Ho Wong, 2 Leah E. Cowen 1
1  Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
2  Faculty of Health Sciences, University of Macau, Macau SAR, China
3  Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
4  Infectious Disease Research Centre, Université Laval, Quebec City, Quebec, Canada
5  Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
6  Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, United States of America
7  Department of Biology, Concordia University, Montreal, Quebec, Canada

Published: 28 March 2018 by Public Library of Science (PLoS) in PLoS Genetics
Public Library of Science (PLoS), Volume 14; 10.1371/journal.pgen.1007270
Abstract: The capacity to respond to temperature fluctuations is critical for microorganisms to survive within mammalian hosts, and temperature modulates virulence traits of diverse pathogens. One key temperature-dependent virulence trait of the fungal pathogen Candida albicans is its ability to transition from yeast to filamentous growth, which is induced by environmental cues at host physiological temperature. A key regulator of temperature-dependent morphogenesis is the molecular chaperone Hsp90, which has complex functional relationships with the transcription factor Hsf1. Although Hsf1 controls global transcriptional remodeling in response to heat shock, its impact on morphogenesis remains unknown. Here, we establish an intriguing paradigm whereby overexpression or depletion of C. albicans HSF1 induces morphogenesis in the absence of external cues. HSF1 depletion compromises Hsp90 function, thereby driving filamentation. HSF1 overexpression does not impact Hsp90 function, but rather induces a dose-dependent expansion of Hsf1 direct targets that drives overexpression of positive regulators of filamentation, including Brg1 and Ume6, thereby bypassing the requirement for elevated temperature during morphogenesis. This work provides new insight into Hsf1-mediated environmentally contingent transcriptional control, implicates Hsf1 in regulation of a key virulence trait, and highlights fascinating biology whereby either overexpression or depletion of a single cellular regulator induces a profound developmental transition.
Keywords: gene expression, polymerase chain reaction, CRISPR, Candida albicans, Hyperexpression techniques, Morphogenesis, Regulator genes, Plasmid construction
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