AUTHOR=Wang Lianfang , Chen Ruilan , Weng Qiuting , Lin Shaoming , Wang Huijun , Li Li , Fuchs Beth Burgwyn , Tan Xiaojiang , Mylonakis Eleftherios 

TITLE=SPT20 Regulates the Hog1-MAPK Pathway and Is Involved in Candida albicans Response to Hyperosmotic Stress

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.00213

DOI=10.3389/fmicb.2020.00213

ISSN=1664-302X

ABSTRACT=<p><italic>Candida albicans</italic> is the most common fungal pathogen and relies on the Hog1-MAPK pathway to resist osmotic stress posed by the environment or during host invasions. Here, we investigated the role of <italic>SPT20</italic> in response to osmotic stress. Testing a <italic>C. albicans spt20</italic>Δ/Δ mutant, we found it was sensitive to osmotic stress. Using sequence alignment, we identified the conserved functional domains between CaSpt20 and ScSpt20. Reconstitution of the Spt20 function in a <italic>spt20</italic>Δ<italic>/CaSPT20</italic> complemented strain found <italic>CaSPT20</italic> can suppress the high sensitivity to hyperosmotic stressors, a cell wall stress agent, and antifungal drugs in the <italic>Saccharomyces cerevisiae spt20</italic>Δ/Δ mutant background. We measured the cellular glycerol accumulation and found it was significantly lower in the <italic>C. albicans spt20</italic>Δ/Δ mutant strain, compared to the wild type strain SC5314 (<italic>P</italic> &lt; 0.001). This result was also supported by quantitative reverse transcription-PCR, which showed the expression levels of gene contributing to glycerol accumulation were reduced in <italic>Caspt20</italic>Δ/Δ compared to wild type (<italic>GPD2</italic> and <italic>TGL1</italic>, <italic>P</italic> &lt; 0.001), while <italic>ADH7</italic> and <italic>AGP2</italic>, whose expression can lead to glycerol decrease, were induced when cells were exposed to high osmolarity (<italic>ADH7</italic>, <italic>P</italic> &lt; 0.001; <italic>AGP2</italic>, <italic>P</italic> = 0.002). In addition, we tested the transcription levels of Hog1-dependent osmotic stress response genes, and found that they were significantly upregulated in wild type cells encountering hyperosmolarity, while the expression of <italic>HGT10</italic>, <italic>SKO1</italic>, <italic>CAT1</italic>, and <italic>SLP3</italic> were not induced when <italic>SPT20</italic> was deleted. Although the transcript of <italic>ORF19.3661</italic> and <italic>ORF19.4370</italic> in <italic>Caspt20Δ/Δ</italic> was induced in the presence of 1 M NaCl, the levels were less than what was observed in the wild type (<italic>ORF19.3661</italic>, <italic>P</italic> = 0.007; <italic>ORF19.4370</italic>, <italic>P</italic> = 0.011). Moreover, the deletion of <italic>CaSPT20</italic> in <italic>C. albicans</italic> reduced phosphorylation levels of Hog1. These findings suggested that <italic>SPT20</italic> is conserved between yeast and <italic>C. albicans</italic> and plays an important role in adapting to osmotic stress through regulating Hog1-MAPK pathway.</p>