Identification of transcription factor <em>HLH3</em> as the master regulator of phosphate acquisition and storage in the human fungal pathogen, <em>Cryptococcus neoformans</em> — ASN Events
  1. Schedule
  2. AMS Proffered Papers
  3. Identification of transcription factor HLH3 as the master regulator of phosphate acquisition and storage in the human fungal pathogen, Cryptococcus neoformans

Identification of transcription factor HLH3 as the master regulator of phosphate acquisition and storage in the human fungal pathogen, Cryptococcus neoformans (#134)

Desmarini Desmarini 1 , Sophia Lev 1 , Yong-Sun Bahn 2 , Julianne Djordjevic 1 3
  1. Centre for Infectious Diseases and Microbiology, Westmead Millennium Institute, Westmead, NSW, Australia
  2. Dept. of Biotechnology College of Life Science and Biotechnology, Yonsei University, Seoul, Korea
  3. Western Clinical School, University of Sydney at Westmead Hospital, Westmead, NSW, Australia

Background and aims Genes encoding plasma membrane transporters of free phosphate (Pi) are essential for virulence of the deadly meningoencephalitis-causing fungal pathogen Cryptococcus neoformans and are up-regulated during infection, suggesting that the pathogen encounters and responds to Pi-limiting conditions in vivo. However, the transcription factors(s) responsible for regulating expression of genes encoding these transporters and proteins involved in mobilizing Pi from extra- and intracellular sources, are unknown.

Methods and Results Here we used a colorimetric enzyme assay which measures the hydrolysis of para-nitrophenol phosphate (pNPP) to screen a C. neoformans transcription factor (TF) knockout library for mutants that fail to secrete Pi-repressible acid phosphate activity derived from Aph1 (the Saccharomyces cerevisiae Pho5 homologue). The screen identified the putative TF, HLH3, which contains the basic helix-loop-helix (HLH) domain present in ScPho4 TF. Using qPCR we demonstrate that all phosphate transporters (PHO84, PHO840, PHO89) and APH1 fail to be induced in the HLH3 mutant (hlh3Δ) during Pi starvation, consistent with the inability of hlh3Δ to mobilize and import Pi from the environment. Growth, and expression of 3 genes encoding intracellular acid phosphatases and 3 genes involved in Pi release from phospholipids, were also abrogated in hlh3Δ during Pi starvation, confirming that Pi mobilization from intracellular sources is also compromised in hlh3Δ.

Conclusions In summary, we have identified HLH3 as the master regulator of Pi homeostasis in C. neoformans and shown that it controls the expression of known and novel Pi-responsive genes involved in mobilization of Pi from external and intracellular sources. 

#2015ASM