A Xenobiotic Detoxification Pathway through Transcriptional Regulation in Filamentous Fungi

Abstract

Fungi are known to utilize transcriptional regulation of genes that encode efflux transporters to detoxify xenobiotics; however, to date it is unknown how fungi transcriptionally regulate and coordinate different phases of detoxification system (phase I, modification; phase II, conjugation; and phase III, secretion). Here we present evidence of an evolutionary convergence between the fungal and mammalian lineages, whereby xenobiotic detoxification genes (phase I coding for cytochrome P450 monooxygenases [CYP450s] and phase III coding for ATP-binding cassette [ABC] efflux transporters) are transcriptionally regulated by structurally unrelated proteins. Following next-generation RNA sequencing (RNA-seq) analyses of a filamentous fungus, Sclerotinia homoeocarpa, the causal agent of dollar spot on turfgrasses, a multidrug resistant (MDR) field strain was found to overexpress phase I and III genes, coding for CYP450s and ABC transporters for xenobiotic detoxification. Furthermore, there was confirmation of a gain-of-function mutation of the fungus-specific transcription factor S. homoeocarpa XDR1 (ShXDR1), which is responsible for constitutive and induced overexpression of the phase I and III genes, resulting in resistance to multiple classes of fungicidal chemicals. This fungal pathogen detoxifies xenobiotics through coordinated transcriptional control of CYP450s, biotransforming xenobiotics with different substrate specificities and ABC transporters, excreting a broad spectrum of xenobiotics or biotransformed metabolites. A Botrytis cinerea strain harboring the mutated ShXDR1 showed increased expression of phase I (BcCYP65) and III (BcatrD) genes, resulting in resistance to fungicides. This indicates the regulatory system is conserved in filamentous fungi. This molecular genetic mechanism for xenobiotic detoxification in fungi holds potential for facilitating discovery of new antifungal drugs and further studies of convergent and divergent evolution of xenobiotic detoxification in eukaryote lineages.

PdMFS1 Transporter Contributes to Penicilliun digitatum Fungicide Resistance and Fungal Virulence during Citrus Fruit Infection

“…In yeast, MFS transporters are controlled by several stress related transcription factors including Yap1, Msn2, Msn4, and Sfp1 [8], and in A. alternata, the transcription of the AaMFS19 MFS transporter is controlled by the Yap1 transcription activator, Hog1, and Fus3 mitogen-activated protein (MAP) kinases [15]. Currently, it has been reported that the expression of efflux transporters is essentially controlled by fungal transcription factors that belong to the zinc cluster (TFs [Zn 2 Cys 6 ]) [5]. The regulation of P. digitatum MFS transporters remains unknown, although previous works revealed that two genes involved in signal transduction pathways, PdSte12 transcription factor and PdSlt2 (MAP) kinase, could act as negative regulators of PdMFS1 and other MFS P. digitatum transporters [18,46].…”

“…The regulation of P. digitatum MFS transporters remains unknown, although previous works revealed that two genes involved in signal transduction pathways, PdSte12 transcription factor and PdSlt2 (MAP) kinase, could act as negative regulators of PdMFS1 and other MFS P. digitatum transporters [18,46]. Besides, it has been described that fungi regulate and coordinate the different stages of the detoxification system by mutations in particular transcription factors [5]. Another system of MFS transporter regulation is the presence of the insertions in MFS promoters as Z. tritici [14] but in this work, no insertions in the promoter region or mutations in the coding region were detected in PdMFS1.…”

“…Knowledge of the mechanisms of fungicide resistance has been extensively explored in recent years [3][4][5]. Among all the mechanisms described, the overexpression of efflux pumps of two classes of transporter proteins that included the ATP-binding cassette (ABC) or the major facilitator superfamily (MFS) transporters has been of greater interest since they can confer resistance towards many unrelated toxic compounds through active transport out of the cell, resulting in decreased intracellular drug concentrations [6].…”

Overexpression of three P450 genes is responsible for resistance to novel pyrimidine amines in Magnaporthe oryzae

“…Overexpression of cytochrome P450s has been reported to cause fungicide resistance via the xenobiotic detoxification pathway in filamentous fungi. 23 To validate whether overexpression of genes Table 2 Effect of temperature on the mycelial growth of resistant isolates of Magnaporthe oryzae and their wild-type parent on PDA without fungicide coding for MoCYP1-1, MoCYP1-2, and MoCYP1-3 was responsible for the resistance observed in this study, the SYP-34773 content was detected by HPLC in the R118-4 and S118 isolates of M. oryzae. Within the concentration range of 1.00-100.00 μg ml −1 , the SYP-34773 quantities detected by HPLC were found to be linear with a correlation coefficient > 0.998.…”

“…[20][21][22] In recent years, a novel molecular mechanism of fungicide resistance via the xenobiotic detoxification pathway in filamentous fungi has been reported through overexpression of cytochrome P450 genes (drug-metabolizing monooxygenases) in Sclerotinia homoeocarpa. 23 The purpose of this study was to: (i) determine the activity of SYP-34773 against M. oryzae under field and laboratory conditions, (ii) investigate the biological characters of SYP-34773-resistant isolates of M. oryzae, and (iii) explore the molecular mechanism that might be responsible for resistance to novel pyrimidine amines. Using RNA-Seq to detect gene transcript patterns, three cytochrome P450 genes were highly expressed in resistant isolates when compared with the parental wild-type isolate.…”