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

Abstract

Candida albicans 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 SPT20 in response to osmotic stress. Testing a C. albicans spt20 / 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 spt20 /CaSPT20 complemented strain found CaSPT20 can suppress the high sensitivity to hyperosmotic stressors, a cell wall stress agent, and antifungal drugs in the Saccharomyces cerevisiae spt20 / mutant background. We measured the cellular glycerol accumulation and found it was significantly lower in the C. albicans spt20 / mutant strain, compared to the wild type strain SC5314 (P < 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 Caspt20 / compared to wild type (GPD2 and TGL1, P < 0.001), while ADH7 and AGP2, whose expression can lead to glycerol decrease, were induced when cells were exposed to high osmolarity (ADH7, P < 0.001; AGP2, P = 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 HGT10, SKO1, CAT1, and SLP3 were not induced when SPT20 was deleted. Although the transcript of ORF19.3661 and ORF19.4370 in Caspt20 / was induced in the presence of 1 M NaCl, the levels were less than what was observed in the wild type (ORF19.3661, P = 0.007; ORF19.4370, P = 0.011). Moreover, the deletion of CaSPT20 in C. albicans reduced phosphorylation levels of Hog1. These findings suggested that SPT20 is conserved between yeast and C. albicans and plays an important role in adapting to osmotic stress through regulating Hog1-MAPK pathway.

SAGA Complex Subunits in Candida albicans Differentially Regulate Filamentation, Invasiveness, and Biofilm Formation

“…We found that conditional mutants spt7 and spt8 were filamentous and invasive in both filamentous inducing and non-inducing conditions while tra1Δ and ngg1Δ were in a yeast-locked state compared to wild type. As well, similar to spt3Δ/Δ and spt20Δ/Δ deleted strains in C. albicans ( Laprade et al, 2002 ; Wang et al, 2020 ), we found cells of the spt7 and spt8 conditional mutants did not separate properly during cell division and appeared clumped together. Also, the spt7 and spt8 repressed mutants formed wrinkled colonies in both inducing and non-inducing conditions—indication of filamentous cells, while the ngg1 and tra1 repressed mutants formed smooth colonies even in the hyphal-inducing conditions of either 10% fetal calf serum (FCS) or Spider media at 37°C for 5 days when compared to the wild type CaSS1 strain (data not shown).…”

“…In S. cerevisiae , the HOG1 pathway controls the synthesis and storage of glycerol which increases intracellular osmotic/turgor pressure to allow cells adapt to high osmotic environments ( Saito and Tatebayashi, 2004 ). Mutations that affect SAGA structural integrity play a critical role for survival at high osmolarity ( Daniel and Grant, 2007 ): the HOG1 MAP kinase pathway recruits SAGA and promotes RNA polymerase II binding to initiate transcription ( Proft and Struhl, 2002 ; Wang et al, 2020 ).…”

Activity of Free and Liposome-Encapsulated Essential Oil from Lavandula angustifolia against Persister-Derived Biofilm of Candida auris

“…The effect of L. angustifolia free and liposome-encapsulated oil on the expression of ERG 11 , ALS 5 , HOG 1 and CDR1 ( Table S1 ) [ 39 , 40 ] in persister-derived biofilms of C. auris was analysed using qRT—PCR. Briefly, persister-derived biofilms were treated with 0.05% v / v oil or liposome-encapsulated oil for 24 h at 37 °C.…”

Clade delineation and isolate-specific variability of Candida albicans exometabolome

“…There are many conditions in which glycerol concentration can increase. Firstly, glycerol is produced and accumulated in cultures and conditions where there is osmotic or citric acid stress -a response mediated via the Hog1 MAPK (high osmolarity glycerol 1 mitogen activated protein kinase) pathway (39,40). We observed during culture that cells were not well suspended in wells.…”