AUTHOR=Barda Omer , Maor Uriel , Sadhasivam Sudharsan , Bi Yang , Zakin Varda , Prusky Dov , Sionov Edward 

TITLE=The pH-Responsive Transcription Factor PacC Governs Pathogenicity and Ochratoxin A Biosynthesis in Aspergillus carbonarius

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.00210

DOI=10.3389/fmicb.2020.00210

ISSN=1664-302X

ABSTRACT=<p>Pathogenic fungi must respond effectively to changes in environmental pH for successful host colonization, virulence and toxin production. <italic>Aspergillus carbonarius</italic> is a mycotoxigenic pathogen with the ability to colonize many plant hosts and secrete ochratoxin A (OTA). In this study, we characterized the functions and addressed the role of PacC-mediated pH signaling in <italic>A. carbonarius</italic> pathogenicity using designed <italic>pacC</italic> gene knockout mutant. Δ<italic>AcpacC</italic> mutant displayed an acidity-mimicking phenotype, which resulted in impaired fungal growth at neutral/alkaline pH, accompanied by reduced sporulation and conidial germination compared to the wild type (WT) strain. The Δ<italic>AcpacC</italic> mutant was unable to efficiently acidify the growth media as a direct result of diminished gluconic and citric acid production. Furthermore, loss of <italic>AcpacC</italic> resulted in a complete inhibition of OTA production at pH 7.0. Additionally, Δ<italic>AcpacC</italic> mutant exhibited attenuated virulence compared to the WT toward grapes and nectarine fruits. Reintroduction of <italic>pacC</italic> gene into Δ<italic>AcpacC</italic> mutant restored the WT phenotype. Our results demonstrate important roles of PacC of <italic>A. carbonarius</italic> in OTA biosynthesis and in pathogenicity by controlling transcription of genes important for fungal secondary metabolism and infection.</p>