Transcription factor CCG-8 plays a pivotal role in azole adaptive responses of Neurospora crassa by regulating intracellular azole accumulation
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Azoles are the most widely used antifungals for controlling fungal infections in clinic and agriculture. Fungi can adapt to azole stress by rapidly activating the transcription of a number of genes, and some of these genes can elevate resistance to azoles. We had reported the transcription factor CCG-8 as a new regulator in the adaptation to antifungal azole stress in Neurospora crassa and Fusarium verticillioides. In this study, we further investigate the mechanisms by which CCG-8 promotes fungal adaptation to azole stress using N. crassa as a model. While deletion of ccg-8 made N. crassa hypersensitive to azoles, ccg-8 overexpression strain was more resistant to azoles than wild type, which further confirmed the positive role of ccg-8 in the adaptation to antifungal azoles. Liquid chromatography–mass spectrometry analysis showed that deletion of ccg-8 resulted in decrease of ergosterol biosynthesis, and high accumulation of toxic sterol 14α-methyl-3,6-diol and ketoconazole (KTC) in the cells, whereas intracellular accumulation of ketoconazole was decreased in the ccg-8 overexpression strain as compared to wild type. For analyzing the effect of CCG-8 on azole export, we tested the contribution of predicted multidrug transporters to azole resistance and found that CDR4 is the major contributor for azole efflux in N. crassa. Interestingly, overexpression of cdr4 or erg11 in the ccg-8 deletion mutant restored its hypersensitive phenotype and overexpression of cdr4 can reduce the level of intracellular KTC. However, the double mutant of ccg-8 and cdr4 was more sensitive than each single mutant, suggesting that drug efflux pump CDR4 plays less contribution for intracellular azole accumulation in the ccg-8 deletion mutant, and CCG-8 may regulate drug uptake. Together, our results revealed that CCG-8 plays a pivotal role in azole adaptive responses of N. crassa by regulating the drug accumulation in the cells.
KeywordsAntifungal resistance ccg-8 Azoles Adaptive responses Neurospora crassa
This project is supported by Grants 31771387 and 31671295 from National Natural Science Foundation of China.
- Dunkel N, Liu TT, Barker KS, Homayouni R, Morschhauser J, Rogers PD (2008) A gain-of-function mutation in the transcription factor Upc2p causes upregulation of ergosterol biosynthesis genes and increased fluconazole resistance in a clinical Candida albicans isolate. Eukaryot Cell 7:1180–1190CrossRefGoogle Scholar
- Hagiwara D, Miura D, Shimizu K, Paul S, Ohba A, Gonoi T, Watanabe A, Kamei K, Shintani T, Moye-Rowley WS, Kawamoto S, Gomi K (2017) A novel Zn2-Cys6 transcription factor AtrR plays a key role in an azole resistance mechanism of Aspergillus fumigatus by co-regulating cyp51A and cdr1B expressions. PLoS Pathog 13:e1006096CrossRefGoogle Scholar
- Sweigard J, Chumley F, Carroll A, Farrall L, Valent. B (1997) A series of vectors for fungal transformation. Fungal Genet Newsl 44:52–53Google Scholar
- Tiwari A, Ngiilmei SD, Tamuli R (2018) The NcZrg-17 gene of Neurospora crassa encodes a cation diffusion facilitator transporter required for vegetative development, tolerance to endoplasmic reticulum stress and cellulose degradation under low zinc conditions. Curr Genet 64:811–819CrossRefGoogle Scholar
- Vogel HJ (1956) A convenient growth medium for Neurospora (Medium N). Microb Genet Bull 13:42–43Google Scholar
- Willger SD, Puttikamonkul S, Kim KH, Burritt JB, Grahl N, Metzler LJ, Barbuch R, Bard M, Lawrence CB, Cramer RA Jr (2008) A sterol-regulatory element binding protein is required for cell polarity, hypoxia adaptation, azole drug resistance, and virulence in Aspergillus fumigatus. PLoS Pathog 4:e1000200CrossRefGoogle Scholar