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Pan KY, Liu HH, Tseng MN, Chang HX. Ca 2+ affects the hyphal differentiation to sclerotia formation of Athelia rolfsii. Microbiol Spectr 2024; 12:e0020024. [PMID: 38687071 PMCID: PMC11237700 DOI: 10.1128/spectrum.00200-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Accepted: 04/05/2024] [Indexed: 05/02/2024] Open
Abstract
RNA-Sequencing (RNA-Seq) and transcriptomic analyses have become powerful tools to study the developmental stages of fungal structures scuh as sclerotia. While RNA-Seq experiments have been set up for many important sclerotia- and microsclerotia-forming fungi, it has not been implemented to study Athelia rolfsii, which is one of the earliest fungi used in literature to uncover the roles of reactive oxygen species (ROS) in stimulating sclerotia formation. This study applied RNA-Seq to profile gene expression in four developmental stages of A. rolfsii sclerotia. Surprisingly, gene ontology and expression patterns suggested that most ROS-scavenging genes were not up-regulated in the stages from hyphal differentiation to the initial sclerotia stage. Using antioxidant and oxidant-amended culture assay, the results suggested none of the ascorbic acid, dithiothreitol (DTT), H2O2, or superoxide dismutase inhibitors [diethyldithiocarbamate (DETC), NaN3, and sodium dodecyl sulfate] affected the sclerotia number. Instead, only glutathione reduced the sclerotia number. Because glutathione has also been suggested to facilitate Ca2+ influx, therefore, glutathione culture assays with the combination of CaCl2, Ca2+-chelator egtazic acid, DETC, and H2O2 were tested on A. rolfsii, as well as two other fungi (Sclerotinia sclerotiorum and Macrophomina phaseolina) for comparison. Although the addition of CaCl2 caused sclerotia or microsclerotia reduction for all three fungi, the CaCl2-ROS interaction was only observed for S. sclerotiorum and M. phaseolina, but not A. rolfsi. Collectively, this study not only pointed out a conserved function of Ca2+ in suppressing fungal sclerotia and microsclerotia formation but also highlighted sclerotia formation of A. rolfsii being only sensitive to Ca2+ and independent of ROS stimuli.IMPORTANCEManagement for plant diseases caused by soil-borne fungal pathogens is challenging because many soil-borne fungal pathogens form sclerotia for long-term survival. Advanced understanding of the molecular and cellular mechanisms of sclerotia formation may provide novel insights to prevent these fungal residues in fields. This study discovered that Ca2+ acts as a negative signal cue to suppress sclerotia and microsclerotia formation in three economically important fungal pathogens. Moreover, the southern blight fungus Athelia rolfsii appears to be only regulated by Ca2+ but not reactive oxygen species. Accordingly, A. rolfsii can be a useful system for studying the detailed mechanism of Ca2+, and the applicability of Ca2+ in reducing sclerotia could be further assessed for disease management.
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Affiliation(s)
- Kuan-Yu Pan
- Department of Plant Pathology and Microbiology, National Taiwan University, Taipei City, Taiwan
| | - Hsien-Hao Liu
- Department of Plant Pathology and Microbiology, National Taiwan University, Taipei City, Taiwan
| | - Min-Nan Tseng
- Kaohsiung District Agricultural Research and Extension Station, Ministry of Agriculture, Pingtung, Taiwan
| | - Hao-Xun Chang
- Department of Plant Pathology and Microbiology, National Taiwan University, Taipei City, Taiwan
- Master Program for Plant Medicine, National Taiwan University, Taipei City, Taiwan
- Center for Biotechnology, National Taiwan University, Taipei City, Taiwan
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Lu P, Wang K, Wang J, Xia C, Yang S, Ma L, Shi H. A novel zinc finger transcription factor, BcMsn2, is involved in growth, development, and virulence in Botrytis cinerea. Front Microbiol 2023; 14:1247072. [PMID: 37915851 PMCID: PMC10616473 DOI: 10.3389/fmicb.2023.1247072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Accepted: 09/20/2023] [Indexed: 11/03/2023] Open
Abstract
Reactive oxygen species (ROS) are important for plant defense against fungal attack. As a necrotrophic fungus, Botrytis cinerea can exploit ROS that originated from both sides of the host and pathogen during interaction to facilitate its infestation. Meanwhile, B. cinerea needs to exert an efficient oxidative stress responsive system to balance the intracellular redox state when encountering deleterious ROS levels. However, the machinery applied by B. cinerea to cope with ROS remains obscure. Herein, we investigated the role of the transcription factor BcMsn2 in regulating B. cinerea redox homeostasis. Disruption of the BcMsn2 gene severely impaired vegetative growth, sclerotium formation, conidial yield, and fungal virulence. The intracellular oxidative homeostasis of the ∆bcmsn2 mutant was disrupted, leading to significantly elevated levels of ROS and reduced activities of enzymes closely associated with oxygen stress, such as catalase (CAT) and superoxide dismutase (SOD). RNA-Seq and qRT-PCR analyses showed remarkable downregulation of the expression of several genes encoding ROS scavenging factors involved in maintaining the redox homeostasis in ∆bcmsn2, suggesting that BcMsn2 functions as a transcriptional regulator of these genes. Our findings indicated that BcMsn2 plays an indispensable role in maintaining the equilibrium of the redox state in B. cinerea, and intracellular ROS serve as signaling molecules that regulate the growth, asexual reproduction, and virulence of this pathogen.
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Affiliation(s)
- Ping Lu
- The Key Laboratory for Quality Improvement of Agricultural Products of Zhejiang Province, College of Advanced Agricultural Sciences, Zhejiang A&F University, Hangzhou, China
| | - Ke Wang
- The Key Laboratory for Quality Improvement of Agricultural Products of Zhejiang Province, College of Advanced Agricultural Sciences, Zhejiang A&F University, Hangzhou, China
| | - Jiaqi Wang
- The Key Laboratory for Quality Improvement of Agricultural Products of Zhejiang Province, College of Advanced Agricultural Sciences, Zhejiang A&F University, Hangzhou, China
| | - Chunbo Xia
- The Key Laboratory for Quality Improvement of Agricultural Products of Zhejiang Province, College of Advanced Agricultural Sciences, Zhejiang A&F University, Hangzhou, China
| | - Shu Yang
- The Key Laboratory for Quality Improvement of Agricultural Products of Zhejiang Province, College of Advanced Agricultural Sciences, Zhejiang A&F University, Hangzhou, China
| | - Liang Ma
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou, China
| | - Haojie Shi
- The Key Laboratory for Quality Improvement of Agricultural Products of Zhejiang Province, College of Advanced Agricultural Sciences, Zhejiang A&F University, Hangzhou, China
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Jiang C, Zhou L, Zhao Q, Wang M, Shen S, Zhao T, Cui K, He L. Selection and Validation of Reference Genes for Reverse-Transcription Quantitative PCR Analysis in Sclerotium rolfsii. Int J Mol Sci 2023; 24:15198. [PMID: 37894879 PMCID: PMC10607518 DOI: 10.3390/ijms242015198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 10/06/2023] [Accepted: 10/09/2023] [Indexed: 10/29/2023] Open
Abstract
Reference genes are important for the accuracy of gene expression profiles using reverse-transcription quantitative PCR (RT-qPCR). However, there are no available reference genes reported for Sclerotium rolfsii; it actually has a pretty diverse and wide host range. In this study, seven candidate reference genes (UBC, β-TUB, 28S, 18S, PGK, EF1α and GAPDH) were validated for their expression stability in S. rolfsii under conditions of different developmental stages, populations, fungicide treatments, photoperiods and pHs. Four algorithm programs (geNorm, Normfinder, Bestkeeper and ΔCt) were used to evaluate the gene expression stability, and RefFinder was used to integrate the ranking results of four programs. Two reference genes were recommended by RefFinder for RT-qPCR normalization in S. rolfsii. The suitable reference genes were GAPDH and UBC across developmental stages, PGK and UBC across populations, GAPDH and PGK across fungicide treatments, EF1α and PGK across photoperiods, β-TUB and EF1α across pHs and PGK and GAPDH across all samples. Four target genes (atrB, PacC, WC1 and CAT) were selected for the validation of the suitability of selected reference genes. However, using one or two reference genes in combination to normalize the expression of target genes showed no significant difference in S. rolfsii. In short, this study provided reliable reference genes for studying the expression and function of genes in S. rolfsii.
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Affiliation(s)
- Chaofan Jiang
- College of Plant Protection, Henan Agricultural University, Zhengzhou 450046, China
- Henan Key Laboratory of Creation and Application of New Pesticide, Henan Agricultural University, No. 218, Ping’an Avenue, Zhengzhou 450046, China
- Henan Research Center of Green Pesticide Engineering and Technology, Henan Agricultural University, Zhengzhou 450046, China
| | - Lin Zhou
- College of Plant Protection, Henan Agricultural University, Zhengzhou 450046, China
- Henan Key Laboratory of Creation and Application of New Pesticide, Henan Agricultural University, No. 218, Ping’an Avenue, Zhengzhou 450046, China
- Henan Research Center of Green Pesticide Engineering and Technology, Henan Agricultural University, Zhengzhou 450046, China
| | - Qingchen Zhao
- College of Plant Protection, Henan Agricultural University, Zhengzhou 450046, China
- Henan Key Laboratory of Creation and Application of New Pesticide, Henan Agricultural University, No. 218, Ping’an Avenue, Zhengzhou 450046, China
- Henan Research Center of Green Pesticide Engineering and Technology, Henan Agricultural University, Zhengzhou 450046, China
| | - Mengke Wang
- College of Plant Protection, Henan Agricultural University, Zhengzhou 450046, China
- Henan Key Laboratory of Creation and Application of New Pesticide, Henan Agricultural University, No. 218, Ping’an Avenue, Zhengzhou 450046, China
- Henan Research Center of Green Pesticide Engineering and Technology, Henan Agricultural University, Zhengzhou 450046, China
| | - Sirui Shen
- College of Plant Protection, Henan Agricultural University, Zhengzhou 450046, China
- Henan Key Laboratory of Creation and Application of New Pesticide, Henan Agricultural University, No. 218, Ping’an Avenue, Zhengzhou 450046, China
- Henan Research Center of Green Pesticide Engineering and Technology, Henan Agricultural University, Zhengzhou 450046, China
| | - Te Zhao
- College of Plant Protection, Henan Agricultural University, Zhengzhou 450046, China
- Henan Key Laboratory of Creation and Application of New Pesticide, Henan Agricultural University, No. 218, Ping’an Avenue, Zhengzhou 450046, China
- Henan Research Center of Green Pesticide Engineering and Technology, Henan Agricultural University, Zhengzhou 450046, China
| | - Kaidi Cui
- College of Plant Protection, Henan Agricultural University, Zhengzhou 450046, China
- Henan Key Laboratory of Creation and Application of New Pesticide, Henan Agricultural University, No. 218, Ping’an Avenue, Zhengzhou 450046, China
- Henan Research Center of Green Pesticide Engineering and Technology, Henan Agricultural University, Zhengzhou 450046, China
| | - Leiming He
- College of Plant Protection, Henan Agricultural University, Zhengzhou 450046, China
- Henan Key Laboratory of Creation and Application of New Pesticide, Henan Agricultural University, No. 218, Ping’an Avenue, Zhengzhou 450046, China
- Henan Research Center of Green Pesticide Engineering and Technology, Henan Agricultural University, Zhengzhou 450046, China
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Katayama T, Maruyama JI. Trace copper-mediated asexual development via a superoxide dismutase and induction of AobrlA in Aspergillus oryzae. Front Microbiol 2023; 14:1135012. [PMID: 36970664 PMCID: PMC10030727 DOI: 10.3389/fmicb.2023.1135012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Accepted: 02/15/2023] [Indexed: 03/11/2023] Open
Abstract
The filamentous fungus Aspergillus oryzae, in which sexual reproduction remains to be discovered, proliferates mainly via asexual spores (conidia). Therefore, despite its industrial importance in food fermentation and recombinant protein production, breeding beneficial strains by genetic crosses is difficult. In Aspergillus flavus, which is genetically close to A. oryzae, structures known as sclerotia are formed asexually, but they are also related to sexual development. Sclerotia are observed in some A. oryzae strains, although no sclerotia formation has been reported in most strains. A better understanding of the regulatory mechanisms underlying sclerotia formation in A. oryzae may contribute to discover its sexual development. Some factors involved in sclerotia formation have been previously identified, but their regulatory mechanisms have not been well studied in A. oryzae. In this study, we found that copper strongly inhibited sclerotia formation and induced conidiation. Deletion of AobrlA encoding a core regulator of conidiation and ecdR involved in transcriptional induction of AobrlA suppressed the copper-mediated inhibition of sclerotia formation, suggesting that AobrlA induction in response to copper leads not only to conidiation but also to inhibition of sclerotia formation. In addition, deletion of the copper-dependent superoxide dismutase (SOD) gene and its copper chaperone gene partially suppressed such copper-mediated induction of conidiation and inhibition of sclerotia formation, indicating that copper regulates asexual development via the copper-dependent SOD. Taken together, our results demonstrate that copper regulates asexual development, such as sclerotia formation and conidiation, via the copper-dependent SOD and transcriptional induction of AobrlA in A. oryzae.
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Affiliation(s)
- Takuya Katayama
- Department of Biotechnology, The University of Tokyo, Tokyo, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo, Japan
| | - Jun-ichi Maruyama
- Department of Biotechnology, The University of Tokyo, Tokyo, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo, Japan
- *Correspondence: Jun-ichi Maruyama,
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Li Y, Li S, Liang Z, Cai Q, Zhou T, Zhao C, Wu X. RNA-seq Analysis of Rhizoctonia solani AG-4HGI Strain BJ-1H Infected by a New Viral Strain of Rhizoctonia solani Partitivirus 2 Reveals a Potential Mechanism for Hypovirulence. PHYTOPATHOLOGY 2022; 112:1373-1385. [PMID: 34965159 DOI: 10.1094/phyto-08-21-0349-r] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Rhizoctonia solani partitivirus 2 (RsPV2), in the genus Alphapartitivirus, confers hypovirulence on R. solani AG-1-IA, the causal agent of rice sheath blight. In this study, a new strain of RsPV2 obtained from R. solani AG-4HGI strain BJ-1H, the causal agent of black scurf on potato, wasidentified and designated as Rhizoctonia solani partitivirus 2 strain BJ-1H (RsPV2-BJ). An RNA sequencing analysis of strain BJ-1H and the virus RsPV2-BJ-free strain BJ-1H-VF derived from strain BJ-1H was conducted to investigate the potential molecular mechanism of hypovirulence induced by RsPV2-BJ. In total, 14,319 unigenes were obtained, and 1,341 unigenes were identified as differentially expressed genes (DEGs), with 570 DEGs being down-regulated and 771 being up-regulated. Notably, several up-regulated DEGs were annotated to cell wall degrading enzymes, including β-1,3-glucanases. Strain BJ-1H exhibited increased expression of β-1,3-glucanase after RsPV2-BJ infection, suggesting that cell wall autolysis activity in R. solani AG-4HGI strain BJ-1H might be promoted by RsPV2-BJ, inducing hypovirulence in its host fungus R. solani AG-4HGI. To the best of our knowledge, this is the first report on the potential mechanism of hypovirulence induced by a mycovirus in R. solani.
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Affiliation(s)
- Yuting Li
- College of Plant Protection, China Agricultural University, Haidian District, Beijing 100193, People's Republic of China
| | - Siwei Li
- College of Plant Protection, China Agricultural University, Haidian District, Beijing 100193, People's Republic of China
| | - Zhijian Liang
- College of Plant Protection, China Agricultural University, Haidian District, Beijing 100193, People's Republic of China
| | - Qingnian Cai
- College of Plant Protection, China Agricultural University, Haidian District, Beijing 100193, People's Republic of China
| | - Tao Zhou
- College of Plant Protection, China Agricultural University, Haidian District, Beijing 100193, People's Republic of China
| | - Can Zhao
- College of Plant Protection, China Agricultural University, Haidian District, Beijing 100193, People's Republic of China
- College of Horticulture, China Agricultural University, Haidian District, Beijing 100193, People's Republic of China
| | - Xuehong Wu
- College of Plant Protection, China Agricultural University, Haidian District, Beijing 100193, People's Republic of China
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Superoxide Initiates the Hyphal Differentiation to Microsclerotia Formation of Macrophomina phaseolina. Microbiol Spectr 2022; 10:e0208421. [PMID: 35080446 PMCID: PMC8791194 DOI: 10.1128/spectrum.02084-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The infection of Macrophomina phaseolina often results in a grayish appearance with numerous survival structures, microsclerotia, on the plant surface. Past works have studied the development of fungal survival structures, sclerotia and microsclerotia, in the Leotiomycetes and Sordariomycetes. However, M. phaseolina belongs to the Dothideomycetes, and it remains unclear whether the mechanism of microsclerotia formation remains conserved among these phylogenetic clades. This study applied RNA-sequencing (RNA-Seq) to profile gene expressions at four stages of microsclerotia formation, and the results suggested that reactive oxygen species (ROS)-related functions were significantly different between the microsclerotia stages and the hyphal stage. Microsclerotia formation was reduced in the plates amended with antioxidants such as ascorbic acid, dithiothreitol (DTT), and glutathione. Surprisingly, DTT drastically scavenged H2O2, but the microsclerotia amount remained similar to the treatment of ascorbic acid and glutathione that both did not completely eliminate H2O2. This observation suggested the importance of O2− over H2O2 in initiating microsclerotia formation. To further validate this hypothesis, the superoxide dismutase 1 (SOD1) inhibitor diethyldithiocarbamate trihydrate (DETC) and H2O2 were tested. The addition of DETC resulted in the accumulation of endogenous O2− and more microsclerotia formation, but the treatment of H2O2 did not. The expression of SOD1 genes were also found to be upregulated in the hyphae to the microsclerotia stage, which suggested a higher endogenous O2− stress presented in these stages. In summary, this study not only showed that the ROS stimulation remained conserved for initiating microsclerotia formation of M. phaseolina but also highlighted the importance of O2− in initiating the hyphal differentiation to microsclerotia formation. IMPORTANCE Reactive oxygen species (ROS) have been proposed as the key stimulus for sclerotia development by studying fungal systems such as Sclerotinia sclerotiorum, and the theory has been adapted for microsclerotia development in Verticillium dahliae and Nomuraea rileyi. While many studies agreed on the association between (micro)sclerotia development and the ROS pathway, which ROS type, superoxide (O2−) or hydrogen peroxide (H2O2), plays a major role in initiating hyphal differentiation to the (micro)sclerotia formation remains controversial, and literature supporting either O2− or H2O2 can be found. This study confirmed the association between ROS and microsclerotia formation for the charcoal rot fungus Macrophomina phaseolina. Moreover, the accumulation of O2− but not H2O2 was found to induce higher density of microsclerotia. By integrating transcriptomic and phenotypic assays, this study presented the first conclusive case for M. phaseolina that O2− is the main ROS stimulus in determining the amount of microsclerotia formation.
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Das P, Effmert U, Baermann G, Quella M, Piechulla B. Impact of bacterial volatiles on phytopathogenic fungi: an in vitro study on microbial competition and interaction. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:596-614. [PMID: 34718549 DOI: 10.1093/jxb/erab476] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 10/27/2021] [Indexed: 06/13/2023]
Abstract
Microorganisms in the rhizosphere are abundant and exist in very high taxonomic diversity. The major players are bacteria and fungi, and bacteria have evolved many strategies to prevail over fungi, among them harmful enzyme activities and noxious secondary metabolites. Interactions between plant growth promoting rhizobacteria and phytopathogenic fungi are potentially valuable since the plant would benefit from fungal growth repression. In this respect, the role of volatile bacterial metabolites in fungistasis has been demonstrated, but the mechanisms of action are less understood. We used three phytopathogenic fungal species (Sclerotinia sclerotiorum, Rhizoctonia solani, and Juxtiphoma eupyrena) as well as one non-phytopathogenic species (Neurospora crassa) and the plant growth promoting rhizobacterium Serratia plymuthica 4Rx13 in co-cultivation assays to investigate the influence of bacterial volatile metabolites on fungi on a cellular level. As a response to the treatment, we found elevated lipid peroxidation, which indirectly reflected the loss of fungal cell membrane integrity. An increase in superoxide dismutase, catalase, and laccase activities indicated oxidative stress. Acclimation to these adverse growth conditions completely restored fungal growth. One of the bioactive bacterial volatile compounds seemed to be ammonia, which was a component of the bacterial volatile mixture. Applied as a single compound in biogenic concentrations ammonia also caused an increase in lipid peroxidation and enzyme activities, but the extent and pattern did not fully match the effect of the entire bacterial volatile mixture.
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Affiliation(s)
- Piyali Das
- Institute of Biological Sciences, Biochemistry, Albert-Einstein-Strasse 3, University of Rostock, 18059 Rostock, Germany
| | - Uta Effmert
- Institute of Biological Sciences, Biochemistry, Albert-Einstein-Strasse 3, University of Rostock, 18059 Rostock, Germany
| | - Gunnar Baermann
- Institute of Biological Sciences, Biochemistry, Albert-Einstein-Strasse 3, University of Rostock, 18059 Rostock, Germany
| | - Manuel Quella
- Institute of Biological Sciences, Biochemistry, Albert-Einstein-Strasse 3, University of Rostock, 18059 Rostock, Germany
| | - Birgit Piechulla
- Institute of Biological Sciences, Biochemistry, Albert-Einstein-Strasse 3, University of Rostock, 18059 Rostock, Germany
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Assays for the Quantification of Antioxidant Enzymes in Fungi. Fungal Biol 2022. [DOI: 10.1007/978-3-030-83749-5_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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9
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Influence of H 2O 2-Induced Oxidative Stress on In Vitro Growth and Moniliformin and Fumonisins Accumulation by Fusarium proliferatum and Fusarium subglutinans. Toxins (Basel) 2021; 13:toxins13090653. [PMID: 34564657 PMCID: PMC8473447 DOI: 10.3390/toxins13090653] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 09/07/2021] [Accepted: 09/13/2021] [Indexed: 11/18/2022] Open
Abstract
Fusarium proliferatum and Fusarium subglutinans are common pathogens of maize which are known to produce mycotoxins, including moniliformin (MON) and fumonisins (FBs). Fungal secondary metabolism and response to oxidative stress are interlaced, where hydrogen peroxide (H2O2) plays a pivotal role in the modulation of mycotoxin production. The objective of this study is to examine the effect of H2O2-induced oxidative stress on fungal growth, as well as MON and FBs production, in different isolates of these fungi. When these isolates were cultured in the presence of 1, 2, 5, and 10 mM H2O2, the fungal biomass of F. subglutinans isolates showed a strong sensitivity to increasing oxidative conditions (27–58% reduction), whereas F. proliferatum isolates were not affected or even slightly improved (45% increase). H2O2 treatment at the lower concentration of 1 mM caused an almost total disappearance of MON and a strong reduction of FBs content in the two fungal species and isolates tested. The catalase activity, surveyed due to its crucial role as an H2O2 scavenger, showed no significant changes at 1 mM H2O2 treatment, thus indicating a lack of correlation with MON and FB changes. H2O2 treatment was also able to reduce MON and FB content in certified maize material, and the same behavior was observed in the presence and absence of these fungi, highlighting a direct effect of H2O2 on the stability of these mycotoxins. Taken together, these data provide insights into the role of H2O2 which, when increased under stress conditions, could affect the vegetative response and mycotoxin production (and degradation) of these fungi.
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10
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Chen M, Chen N, Wu T, Bian Y, Deng Y, Xu Z. Characterization of Two Mitochondrial Genomes and Gene Expression Analysis Reveal Clues for Variations, Evolution, and Large-Sclerotium Formation in Medical Fungus Wolfiporia cocos. Front Microbiol 2020; 11:1804. [PMID: 32849413 PMCID: PMC7417453 DOI: 10.3389/fmicb.2020.01804] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Accepted: 07/09/2020] [Indexed: 12/05/2022] Open
Abstract
Wolfiporia cocos, a precious mushroom with a long history as an edible food and Asian traditional medicine, remains unclear in the genetic mechanism underlying the formation of large sclerotia. Here, two complete circular mitogenomes (BL16, 135,686 bp and MD-104 SS10, 124,842 bp, respectively) were presented in detail first. The salient features in the mitogenomes of W. cocos include an intron in the tRNA (trnQ-UUG2), and an obvious gene rearrangement identified between the two mitogenomes from the widely geographically separated W. cocos strains. Genome comparison and phylogenetic analyses reveal some variations and evolutional characteristics in W. cocos. Whether the mitochondrion is functional in W. cocos sclerotium development was investigated by analyzing the mitogenome synteny of 10 sclerotium-forming fungi and mitochondrial gene expression patterns in different W. cocos sclerotium-developmental stages. Three common homologous genes identified across ten sclerotium-forming fungi were also found to exhibit significant differential expression levels during W. cocos sclerotium development. Most of the mitogenomic genes are not expressed in the mycelial stage but highly expressed in the sclerotium initial or developmental stage. These results indicate that some of mitochondrial genes may play a role in the development of sclerotium in W. cocos, which needs to be further elucidated in future studies. This study will stimulate new ideas on cytoplasmic inheritance of W. cocos and facilitate the research on the role of mitochondria in large sclerotium formation.
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Affiliation(s)
- Mengting Chen
- Institute of Applied Mycology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Naiyao Chen
- Institute of Applied Mycology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Ting Wu
- Institute of Applied Mycology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Yinbing Bian
- Institute of Applied Mycology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Agro-Microbial Resource Comprehensive Utilization, Ministry of Agriculture, Huazhong Agricultural University, Wuhan, China
| | - Youjin Deng
- Center for Genomics and Biotechnology, Haixia Institute of Science and Technology, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zhangyi Xu
- Institute of Applied Mycology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Agro-Microbial Resource Comprehensive Utilization, Ministry of Agriculture, Huazhong Agricultural University, Wuhan, China
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11
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Zhang J, Wang Y, Du J, Huang Z, Fang A, Yang Y, Bi C, Qing L, Yu Y. Sclerotinia sclerotiorum Thioredoxin Reductase Is Required for Oxidative Stress Tolerance, Virulence, and Sclerotial Development. Front Microbiol 2019; 10:233. [PMID: 30837967 PMCID: PMC6382746 DOI: 10.3389/fmicb.2019.00233] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 01/28/2019] [Indexed: 01/25/2023] Open
Abstract
Sclerotinia sclerotiorum is a destructive ascomycete plant pathogen with worldwide distribution. Extensive research on different aspects of this pathogen's capability to cause disease will help to uncover clues about new ways to safely control Sclerotinia diseases. The thioredoxin (Trx) system consists of Trx and thioredoxin reductase (TrxR), which play critical roles in maintenance of cellular redox homeostasis. In this study, we functionally characterized a gene encoding a TrxR (SsTrr1) in S. sclerotiorum. The amino acids of SsTrr1 exhibited high similarity with reported TrxRs in plant pathogens and targeted silencing of SsTrr1 lead to a decrease in TrxR activities of mycelium. SsTrr1 showed high expression levels during hyphae growth, and the levels decreased at the different stages of sclerotial development. SsTrr1 gene-silenced strains produced a smaller number of larger sclerotia on potato dextrose agar medium. The observations were consistent with the inhibitory effects on sclerotial development by the TrxR inhibitor, anrunofin. The expression of SsTrr1 showed a dramatic increase under the oxidative stress and the hyphal growth of gene-silenced strains showed more sensitivity to H2O2. SsTrr1 gene-silenced strains also showed impaired virulence in different hosts. Taken together, our results suggest that SsTrr1 encodes a TrxR that is of great important for oxidative stress tolerance, virulence, and sclerotial development of S. sclerotiorum.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Yang Yu
- College of Plant Protection, Southwest University, Chongqing, China
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12
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Evaluation of colorimetric assays for determination of H 2O 2in planta during fungal wood decomposition. J Microbiol Methods 2017; 145:10-13. [PMID: 29242076 DOI: 10.1016/j.mimet.2017.12.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 12/08/2017] [Accepted: 12/09/2017] [Indexed: 01/22/2023]
Abstract
Hydrogen peroxide (H2O2) plays a critical role in generating oxygen radicals as fungi attack and deconstruct plant cell walls. Its concentrations in planta, however, are often low during decomposition and evade detection by traditional methods. Here, we compared relevant methods and selected the best based on detection limits and selectivity.
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13
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Tolerance and stress response of sclerotiogenic Aspergillus oryzae G15 to copper and lead. Folia Microbiol (Praha) 2017; 62:295-304. [DOI: 10.1007/s12223-017-0494-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 01/12/2017] [Indexed: 11/25/2022]
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14
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Ray S, Singh V, Singh S, Sarma BK, Singh HB. Biochemical and histochemical analyses revealing endophytic Alcaligenes faecalis mediated suppression of oxidative stress in Abelmoschus esculentus challenged with Sclerotium rolfsii. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2016; 109:430-441. [PMID: 27816824 DOI: 10.1016/j.plaphy.2016.10.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 09/27/2016] [Accepted: 10/22/2016] [Indexed: 06/06/2023]
Abstract
Sclerotium rolfsii is a highly aggressive pathogen that causes huge economic losses, especially in temperate climates. Alcaligenes faecalis, particularly in endophytic form, has rarely been used to control this fungus. In this study, endophytic Alcaligenes sp. strain BHU 12, BHU 16 (isolated from Abelmoschus esculentus leaf) and BHU M7 (isolated from Andrographis paniculata leaf) were reported to trigger a wide range of host defenses in Okra plant against the collar-rot pathogen S. rolfsii. Endophytic colonization of the strains in ten days old plants was assessed through re-isolation of the rif-tagged strains on rifampicin augmented nutrient agar media. The ability of the endophytic strains to induce systemic defense responses in above-ground organs was assessed by collecting leaf tissues of the Okra plants grown under non-gnotobiotic conditions at different time intervals post seedling bacterization with the endophytic biocontrol agents. The pathogen challenged unprimed plants exhibited flaccidity of the stem and leaves at 48 h post infection (hpi) in contrast to the bioprimed and challenged plants. Biochemical and histochemical analyses explained the above phenomenon as activation of phyto-peroxidases leading to an increased metabolism of the reactive oxygen species (ROS), accompanied by activation of the phenylpropanoid network and a subsequent enhancement in plant phenolics. Interestingly, though the maximum increase in the defense pathways was observed in treatments with native endophytes of Okra plant, yet the enhancement in antioxidant pathway due to A. paniculata borne endophytes was also quite significant. Thus, this work clearly demonstrates how Okra plants respond to the "non-hostile" colonization of bacterial endophytes and how induced defense response can contribute to the biocontrol activity of the endophytic strains.
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Affiliation(s)
- Shatrupa Ray
- Department of Botany, Institute of Science, Banaras Hindu University, India
| | - Vivek Singh
- Department of Botany, Institute of Science, Banaras Hindu University, India; Department of Mycology and Plant Pathology, Institute of Agricultural Sciences, Banaras Hindu University, India
| | - Surendra Singh
- Department of Botany, Institute of Science, Banaras Hindu University, India
| | - Birinchi Kumar Sarma
- Department of Mycology and Plant Pathology, Institute of Agricultural Sciences, Banaras Hindu University, India
| | - Harikesh Bahadur Singh
- Department of Mycology and Plant Pathology, Institute of Agricultural Sciences, Banaras Hindu University, India.
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15
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Zámocký M, Tafer H, Chovanová K, Lopandic K, Kamlárová A, Obinger C. Genome sequence of the filamentous soil fungus Chaetomium cochliodes reveals abundance of genes for heme enzymes from all peroxidase and catalase superfamilies. BMC Genomics 2016; 17:763. [PMID: 27681232 PMCID: PMC5041501 DOI: 10.1186/s12864-016-3111-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 09/22/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The ascomycetous family Chaetomiaceae (class Sordariomycetes) includes numerous soilborn, saprophytic, endophytic and pathogenic fungi which can adapt to various growth conditions and living niches by providing a broad armory of oxidative and antioxidant enzymes. RESULTS We release the 34.7 Mbp draft genome of Chaetomium cochliodes CCM F-232 consisting of 6036 contigs with an average size of 5756 bp and reconstructed its phylogeny. We show that this filamentous fungus is closely related but not identical to Chaetomium globosum and Chaetomium elatum. We screened and critically analysed this genome for open reading frames coding for essential antioxidant enzymes. It is demonstrated that the genome of C. cochliodes contains genes encoding putative enzymes from all four known heme peroxidase superfamilies including bifunctional catalase-peroxidase (KatG), cytochrome c peroxidase (CcP), manganese peroxidase, two paralogs of hybrid B peroxidases (HyBpox), cyclooxygenase, linoleate diol synthase, dye-decolorizing peroxidase (DyP) of type B and three paralogs of heme thiolate peroxidases. Both KatG and DyP-type B are shown to be introduced into ascomycetes genomes by horizontal gene transfer from various bacteria. In addition, two putative large subunit secretory and two small-subunit typical catalases are found in C. cochliodes. We support our genomic findings with quantitative transcription analysis of nine peroxidase & catalase genes. CONCLUSIONS We delineate molecular phylogeny of five distinct gene superfamilies coding for essential heme oxidoreductases in Chaetomia and from the transcription analysis the role of this antioxidant enzymatic armory for the survival of a peculiar soil ascomycete in various harsh environments.
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Affiliation(s)
- Marcel Zámocký
- Department of Chemistry, Division of Biochemistry, University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
- Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská cesta 21, SK-84551 Bratislava, Slovakia
| | - Hakim Tafer
- Department of Biotechnology, University of Natural Resources and Life Sciences, Muthgasse 11, A-1190 Vienna, Austria
| | - Katarína Chovanová
- Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská cesta 21, SK-84551 Bratislava, Slovakia
| | - Ksenija Lopandic
- Department of Biotechnology, University of Natural Resources and Life Sciences, Muthgasse 11, A-1190 Vienna, Austria
| | - Anna Kamlárová
- Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská cesta 21, SK-84551 Bratislava, Slovakia
| | - Christian Obinger
- Department of Chemistry, Division of Biochemistry, University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
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16
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Bashi ZD, Gyawali S, Bekkaoui D, Coutu C, Lee L, Poon J, Rimmer SR, Khachatourians GG, Hegedus DD. The Sclerotinia sclerotiorum Slt2 mitogen-activated protein kinase ortholog, SMK3, is required for infection initiation but not lesion expansion. Can J Microbiol 2016; 62:836-850. [PMID: 27503454 DOI: 10.1139/cjm-2016-0091] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Mitogen-activated protein kinases (MAPKs) play a central role in transferring signals and regulating gene expression in response to extracellular stimuli. An ortholog of the Saccharomyces cerevisiae cell wall integrity MAPK was identified in the phytopathogenic fungus Sclerotinia sclerotiorum. Disruption of the S. sclerotiorum Smk3 gene severely reduced virulence on intact host plant leaves but not on leaves stripped of cuticle wax. This was attributed to alterations in hyphal apical dominance leading to the inability to aggregate and form infection cushions. The mutation also caused loss of the ability to produce sclerotia, increased aerial hyphae formation, and altered hyphal hydrophobicity and cell wall integrity. Mutants had slower radial expansion rates on solid media but more tolerance to elevated temperatures. Loss of the SMK3 cell wall integrity MAPK appears to have impaired the ability of S. sclerotiorum to sense its surrounding environment, leading to misregulation of a variety of functions. Many of the phenotypes were similar to those observed in S. sclerotiorum adenylate cyclase and SMK1 MAPK mutants, suggesting that these signaling pathways co-regulate aspects of fungal growth, physiology, and pathogenicity.
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Affiliation(s)
- Zafer Dallal Bashi
- a Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N OX2, Canada.,b Department of Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada
| | - Sanjaya Gyawali
- a Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N OX2, Canada
| | - Diana Bekkaoui
- a Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N OX2, Canada
| | - Cathy Coutu
- a Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N OX2, Canada
| | - Leora Lee
- a Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N OX2, Canada
| | - Jenny Poon
- a Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N OX2, Canada
| | - S Roger Rimmer
- a Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N OX2, Canada
| | - George G Khachatourians
- b Department of Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada
| | - Dwayne D Hegedus
- a Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N OX2, Canada.,b Department of Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada
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17
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De novo assembly and transcriptome analysis of sclerotial development in Wolfiporia cocos. Gene 2016; 588:149-55. [PMID: 27185634 DOI: 10.1016/j.gene.2016.05.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2016] [Revised: 05/06/2016] [Accepted: 05/12/2016] [Indexed: 01/19/2023]
Abstract
Wolfiporia cocos Ryvarden et Gilbertson, a well-known medicinal fungus in the Basidiomycetes, is widely distributed in East Asia. Its dried sclerotium, which is known as Fuling in China, has been used as a traditional crude drug in Chinese traditional medicine for thousand years. However, little is known about how the sclerotium is developed at the genetic level. In this study, the de novo sequencing of sclerotia of W. cocos (S1_initial stage; S2_developmental stage and S3_mature stage) was carried out by illumina HiSeq 2000 technology. 27,438 unigenes were assembled from ~30Gbp raw data, and 12,093 unigenes were significantly annotated. The analysis of expression profiles during development returned 304 differentially expressed genes (DEGs), which were clustered into four different groups according to their expression trends. Especially for the maturation stage (S3), the sclerotium exhibited a markedly different expression profile from other stages. We further showed that peroxisome, unsaturation of fatty acids and degradation pathway were respectively prevalent in S1, S2 and S3 stages as evidenced by enrichment analysis. To our knowledge, this study represents the first report of sclerotial development transcriptomics in W. cocos. The obtained results provide novel insights into the developmental biology of the sclerotia, which is helpful for future studies about cultivation and breeding of W. cocos.
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18
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Hegedus DD, Gerbrandt K, Coutu C. The eukaryotic protein kinase superfamily of the necrotrophic fungal plant pathogen, Sclerotinia sclerotiorum. MOLECULAR PLANT PATHOLOGY 2016; 17:634-647. [PMID: 26395470 PMCID: PMC6638376 DOI: 10.1111/mpp.12321] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Protein kinases have been implicated in the regulation of many processes that guide pathogen development throughout the course of infection. A survey of the Sclerotinia sclerotiorum genome for genes encoding proteins containing the highly conserved eukaryotic protein kinase (ePK) domain, the largest protein kinase superfamily, revealed 92 S. sclerotiorum ePKs. This review examines the composition of the S. sclerotiorum ePKs based on conserved motifs within the ePK domain family, and relates this to orthologues found in other filamentous fungi and yeasts. The ePKs are also discussed in terms of their proposed role(s) in aspects of host pathogenesis, including the coordination of mycelial growth/development and deployment of pathogenicity determinants in response to environmental stimuli, nutrients and stress.
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Affiliation(s)
- Dwayne D Hegedus
- Agriculture and Agri-Food Canada, Saskatoon, SK, Canada, S7N 0X2
- Department of Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, SK, Canada, S7N 5A9
| | - Kelsey Gerbrandt
- Agriculture and Agri-Food Canada, Saskatoon, SK, Canada, S7N 0X2
| | - Cathy Coutu
- Agriculture and Agri-Food Canada, Saskatoon, SK, Canada, S7N 0X2
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Liu MM, Xing YM, Guo SX. Diversity Analysis of Polyporus umbellatus in China Using Inter-simple Sequence Repeat (ISSR) Markers. Biol Pharm Bull 2015. [DOI: 10.1248/bpb.b15-00274] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Meng-Meng Liu
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College
| | - Yong-Mei Xing
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College
| | - Shun-Xing Guo
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College
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20
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Song C, Liu M, Xing Y, Guo S. ESTs analysis of putative genes engaged in Polyporus umbellatus sclerotial development. Int J Mol Sci 2014; 15:15951-62. [PMID: 25210845 PMCID: PMC4200805 DOI: 10.3390/ijms150915951] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2014] [Revised: 08/13/2014] [Accepted: 09/02/2014] [Indexed: 12/18/2022] Open
Abstract
Polyporus umbellatus is one of the most widely used and precious medicinal fungi and the underground sclerotia are known to be with great medicinal value. However, the molecular mechanisms involved in sclerotial development are poorly understood. In the present study, we constructed a forward suppression subtractive hybridization (SSH) cDNA library of Polyporus umbellatus to identify genes expressing differently between mycelium and sclerotia. In this library, a total of 1202 clones were sequenced, assembled into 222 contigs and 524 singletons which were further searched against the NCBI nonredundant (NR) protein database (E-value cutoff, 10−5). Based on sequence similarity with known proteins, 378 sequences between mycelium and sclerotial were identified and classified into different functional categories through Gene Ontology (GO), Clusters of orthologous Groups of proteins (COGs). We have finally identified a majority of differentially expressed genes (constituting 5.6% of the present library) between the two different periods. An expression level of 32 selected expressed sequence tags (ESTs) generated from the above SSH cDNA library was studied through RT-PCR. This study provides the first global overview of genes putatively involved in Polyporus umbellatus sclerotial development and provides a preliminary basis for further functional research in terms of regulated gene expression in sclerotial production.
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Affiliation(s)
- Chao Song
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100193, China.
| | - Mengmeng Liu
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100193, China.
| | - Yongmei Xing
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100193, China.
| | - Shunxing Guo
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100193, China.
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Role of oxidative stress in Sclerotial differentiation and aflatoxin B1 biosynthesis in Aspergillus flavus. Appl Environ Microbiol 2014; 80:5561-71. [PMID: 25002424 DOI: 10.1128/aem.01282-14] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
We show here that oxidative stress is involved in both sclerotial differentiation (SD) and aflatoxin B1 biosynthesis in Aspergillus flavus. Specifically, we observed that (i) oxidative stress regulates SD, as implied by its inhibition by antioxidant modulators of reactive oxygen species and thiol redox state, and that (ii) aflatoxin B1 biosynthesis and SD are comodulated by oxidative stress. However, aflatoxin B1 biosynthesis is inhibited by lower stress levels compared to SD, as shown by comparison to undifferentiated A. flavus. These same oxidative stress levels also characterize a mutant A. flavus strain, lacking the global regulatory gene veA. This mutant is unable to produce sclerotia and aflatoxin B1. (iii) Further, we show that hydrogen peroxide is the main modulator of A. flavus SD, as shown by its inhibition by both an irreversible inhibitor of catalase activity and a mimetic of superoxide dismutase activity. On the other hand, aflatoxin B1 biosynthesis is controlled by a wider array of oxidative stress factors, such as lipid hydroperoxide, superoxide, and hydroxyl and thiyl radicals.
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