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Martín JF, Liras P. Targeting of Specialized Metabolites Biosynthetic Enzymes to Membranes and Vesicles by Posttranslational Palmitoylation: A Mechanism of Non-Conventional Traffic and Secretion of Fungal Metabolites. Int J Mol Sci 2024; 25:1224. [PMID: 38279221 PMCID: PMC10816013 DOI: 10.3390/ijms25021224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 12/30/2023] [Accepted: 01/09/2024] [Indexed: 01/28/2024] Open
Abstract
In nature, the formation of specialized (secondary) metabolites is associated with the late stages of fungal development. Enzymes involved in the biosynthesis of secondary metabolites in fungi are located in distinct subcellular compartments including the cytosol, peroxisomes, endosomes, endoplasmic reticulum, different types of vesicles, the plasma membrane and the cell wall space. The enzymes traffic between these subcellular compartments and the secretion through the plasma membrane are still unclear in the biosynthetic processes of most of these metabolites. Recent reports indicate that some of these enzymes initially located in the cytosol are later modified by posttranslational acylation and these modifications may target them to membrane vesicle systems. Many posttranslational modifications play key roles in the enzymatic function of different proteins in the cell. These modifications are very important in the modulation of regulatory proteins, in targeting of proteins, intracellular traffic and metabolites secretion. Particularly interesting are the protein modifications by palmitoylation, prenylation and miristoylation. Palmitoylation is a thiol group-acylation (S-acylation) of proteins by palmitic acid (C16) that is attached to the SH group of a conserved cysteine in proteins. Palmitoylation serves to target acylated proteins to the cytosolic surface of cell membranes, e.g., to the smooth endoplasmic reticulum, whereas the so-called toxisomes are formed in trichothecene biosynthesis. Palmitoylation of the initial enzymes involved in the biosynthesis of melanin serves to target them to endosomes and later to the conidia, whereas other non-palmitoylated laccases are secreted directly by the conventional secretory pathway to the cell wall space where they perform the last step(s) of melanin biosynthesis. Six other enzymes involved in the biosynthesis of endocrosin, gliotoxin and fumitremorgin believed to be cytosolic are also targeted to vesicles, although it is unclear if they are palmitoylated. Bioinformatic analysis suggests that palmitoylation may be frequent in the modification and targeting of polyketide synthetases and non-ribosomal peptide synthetases. The endosomes may integrate other small vesicles with different cargo proteins, forming multivesicular bodies that finally fuse with the plasma membrane during secretion. Another important effect of palmitoylation is that it regulates calcium metabolism by posttranslational modification of the phosphatase calcineurin. Mutants defective in the Akr1 palmitoyl transferase in several fungi are affected in calcium transport and homeostasis, thus impacting on the biosynthesis of calcium-regulated specialized metabolites. The palmitoylation of secondary metabolites biosynthetic enzymes and their temporal distribution respond to the conidiation signaling mechanism. In summary, this posttranslational modification drives the spatial traffic of the biosynthetic enzymes between the subcellular organelles and the plasma membrane. This article reviews the molecular mechanism of palmitoylation and the known fungal palmitoyl transferases. This novel information opens new ways to improve the biosynthesis of the bioactive metabolites and to increase its secretion in fungi.
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Affiliation(s)
- Juan F. Martín
- Departamento de Biología Molecular, Área de Microbiología, Universidad de León, 24071 León, Spain;
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Wang Y, Yang M, Ge F, Jiang B, Hu R, Zhou X, Yang Y, Liu M. Lysine Succinylation of VBS Contributes to Sclerotia Development and Aflatoxin Biosynthesis in Aspergillus flavus. Mol Cell Proteomics 2023; 22:100490. [PMID: 36566904 PMCID: PMC9879794 DOI: 10.1016/j.mcpro.2022.100490] [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: 06/10/2022] [Revised: 12/06/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022] Open
Abstract
Aspergillus flavus is a common saprophytic and pathogenic fungus, and its secondary metabolic pathways are one of the most highly characterized owing to its aflatoxin (AF) metabolite affecting global economic crops and human health. Different natural environments can cause significant variations in AF synthesis. Succinylation was recently identified as one of the most critical regulatory post-translational modifications affecting metabolic pathways. It is primarily reported in human cells and bacteria with few studies on fungi. Proteomic quantification of lysine succinylation (Ksuc) exploring its potential involvement in secondary metabolism regulation (including AF production) has not been performed under natural conditions in A. flavus. In this study, a quantification method was performed based on tandem mass tag labeling and antibody-based affinity enrichment of succinylated peptides via high accuracy nano-liquid chromatography with tandem mass spectrometry to explore the succinylation mechanism affecting the pathogenicity of naturally isolated A. flavus strains with varying toxin production. Altogether, 1240 Ksuc sites in 768 proteins were identified with 1103 sites in 685 proteins quantified. Comparing succinylated protein levels between high and low AF-producing A. flavus strains, bioinformatics analysis indicated that most succinylated proteins located in the AF biosynthetic pathway were downregulated, which directly affected AF synthesis. Versicolorin B synthase is a key catalytic enzyme for heterochrome B synthesis during AF synthesis. Site-directed mutagenesis and biochemical studies revealed that versicolorin B synthase succinylation is an important regulatory mechanism affecting sclerotia development and AF biosynthesis in A. flavus. In summary, our quantitative study of the lysine succinylome in high/low AF-producing strains revealed the role of Ksuc in regulating AF biosynthesis. We revealed novel insights into the metabolism of AF biosynthesis using naturally isolated A. flavus strains and identified a rich source of metabolism-related enzymes regulated by succinylation.
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Affiliation(s)
- Yu Wang
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, Key Laboratory of Magnetic Resonance in Biological Systems, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences - Wuhan National Laboratory for Optoelectronics, Hubei Optics Valley Laboratory, Wuhan, China; University of Chinese Academy of Sciences, Beijing, China
| | - Mingkun Yang
- University of Chinese Academy of Sciences, Beijing, China; State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China
| | - Feng Ge
- University of Chinese Academy of Sciences, Beijing, China; State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China
| | - Bin Jiang
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, Key Laboratory of Magnetic Resonance in Biological Systems, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences - Wuhan National Laboratory for Optoelectronics, Hubei Optics Valley Laboratory, Wuhan, China; University of Chinese Academy of Sciences, Beijing, China.
| | - Rui Hu
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, Key Laboratory of Magnetic Resonance in Biological Systems, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences - Wuhan National Laboratory for Optoelectronics, Hubei Optics Valley Laboratory, Wuhan, China; University of Chinese Academy of Sciences, Beijing, China.
| | - Xin Zhou
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, Key Laboratory of Magnetic Resonance in Biological Systems, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences - Wuhan National Laboratory for Optoelectronics, Hubei Optics Valley Laboratory, Wuhan, China; University of Chinese Academy of Sciences, Beijing, China
| | - Yunhuang Yang
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, Key Laboratory of Magnetic Resonance in Biological Systems, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences - Wuhan National Laboratory for Optoelectronics, Hubei Optics Valley Laboratory, Wuhan, China; University of Chinese Academy of Sciences, Beijing, China
| | - Maili Liu
- State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, Key Laboratory of Magnetic Resonance in Biological Systems, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences - Wuhan National Laboratory for Optoelectronics, Hubei Optics Valley Laboratory, Wuhan, China; University of Chinese Academy of Sciences, Beijing, China
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Skellam E. Subcellular localization of fungal specialized metabolites. Fungal Biol Biotechnol 2022; 9:11. [PMID: 35614515 PMCID: PMC9134587 DOI: 10.1186/s40694-022-00140-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2022] [Accepted: 05/10/2022] [Indexed: 01/07/2023] Open
Abstract
Fungal specialized metabolites play an important role in the environment and have impacted human health and survival significantly. These specialized metabolites are often the end product of a series of sequential and collaborating biosynthetic enzymes that reside within different subcellular compartments. A wide variety of methods have been developed to understand fungal specialized metabolite biosynthesis in terms of the chemical conversions and the biosynthetic enzymes required, however there are far fewer studies elucidating the compartmentalization of the same enzymes. This review illustrates the biosynthesis of specialized metabolites where the localization of all, or some, of the biosynthetic enzymes have been determined and describes the methods used to identify the sub-cellular localization.
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Affiliation(s)
- Elizabeth Skellam
- Department of Chemistry and BioDiscovery Institute, University of North Texas, 1155 Union Circle, Denton, TX, 76201, USA.
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Ren S, Yue Y, Li Y, Guo X, Wang S. Functional analyses of the versicolorin B synthase gene in Aspergillus flavus. Microbiologyopen 2017; 6. [PMID: 28612469 PMCID: PMC5552937 DOI: 10.1002/mbo3.471] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2016] [Revised: 01/26/2017] [Accepted: 02/08/2017] [Indexed: 02/06/2023] Open
Abstract
Aflatoxin is a toxic, carcinogenic mycotoxin primarily produced by Aspergillus parasiticus and Aspergillus flavus. Previous studies have predicted the existence of more than 20 genes in the gene cluster involved in aflatoxin biosynthesis. Among these genes, aflK encodes versicolorin B synthase, which converts versiconal to versicolorin B. Past research has investigated aflK in A. parasiticus, but few studies have characterized aflK in the animal, plant, and human pathogen A. flavus. To understand the potential role of aflK in A. flavus, its function was investigated here for the first time using gene replacement and gene complementation strategies. The aflK deletion-mutant ΔaflK exhibited a significant decrease in sclerotial production and aflatoxin biosynthesis compared with wild-type and the complementation strain ΔaflK::aflK. ΔaflK did not affect the ability of A. flavus to infect seeds, but downregulated aflatoxin production after seed infection. This is the first report of a relationship between aflK and sclerotial production in A. flavus, and our findings indicate that aflK regulates aflatoxin formation.
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Affiliation(s)
- Silin Ren
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yuewei Yue
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yu Li
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xiaodong Guo
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Shihua Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, and School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
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Lee JW, Roze LV, Linz JE. Evidence that a wortmannin-sensitive signal transduction pathway regulates aflatoxin biosynthesis. Mycologia 2017. [DOI: 10.1080/15572536.2007.11832550] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Joo-Won Lee
- Department of Pharmacology, Institute of Biomedical Science, Hanyang University, Seoul, South Korea
| | - Ludmila V. Roze
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan
| | - John E. Linz
- Department of Food Science and Human Nutrition, Department of Microbiology and Molecular Genetics, National Food Safety and Toxicology Center, 234B GM Trout Building, Michigan State University, East Lansing, Michigan 48823
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Ye X, Liu H, Jin Y, Guo M, Huang A, Chen Q, Guo W, Zhang F, Feng L. Transcriptomic Analysis of Calonectria pseudoreteaudii during Various Stages of Eucalyptus Infection. PLoS One 2017; 12:e0169598. [PMID: 28072879 PMCID: PMC5224884 DOI: 10.1371/journal.pone.0169598] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2016] [Accepted: 12/19/2016] [Indexed: 01/03/2023] Open
Abstract
Eucalyptus leaf blight caused by Calonectria spp. is a serious disease in Eucalyptus seedling and plantations. However, the molecular mechanisms of the infection process and pathogenesis of Calonectria to Eucalyptus is not well-studied. In this study, we analyzed the transcriptomes of C. pseudoreteaudii at three stages of Eucalyptus leaf infection, and in mycelium grown in potato dextrose broth using Illumina RNA-Seq technology. We identified 161 differentially expressed genes between C. pseudoreteaudii from leaf and mycelium grown in potato dextrose broth. GO and KEGG enrichment analyses of these genes suggested that they were mainly involved in oxidoreductase activity, hydrolase activity, and transmembrane transporter activity. Most of the differentially expressed genes at the early infection stage were upregulated. These upregulated genes were mainly involved in cell wall hydrolysis and toxin synthesis, suggesting a role for toxin and cell wall hydrolases in the establishment of Calonectria leaf blight. Genes related to detoxification of phytoalexins were continually upregulated during infection. The candidate effectors and putative pathogenicity determinants identified in this study will help in the functional analysis of C. pseudoreteaudii virulence and pathogenicity.
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Affiliation(s)
- Xiaozhen Ye
- Forestry College, Fujian Agriculture and Forestry University, Fuzhou, China
- Jinshan College, Fujian Agriculture and Forestry University, Fuzhou, China
- Institute of Forestry Protection, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Hongyi Liu
- Forestry College, Fujian Agriculture and Forestry University, Fuzhou, China
- Institute of Forestry Protection, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yajie Jin
- Forestry College, Fujian Agriculture and Forestry University, Fuzhou, China
- Institute of Forestry Protection, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Mengmeng Guo
- Forestry College, Fujian Agriculture and Forestry University, Fuzhou, China
- Institute of Forestry Protection, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Aizhen Huang
- Forestry College, Fujian Agriculture and Forestry University, Fuzhou, China
- Institute of Forestry Protection, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Quanzhu Chen
- Jinshan College, Fujian Agriculture and Forestry University, Fuzhou, China
- Institute of Forestry Protection, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Wenshuo Guo
- Forestry College, Fujian Agriculture and Forestry University, Fuzhou, China
- Institute of Forestry Protection, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Feiping Zhang
- Forestry College, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Lizhen Feng
- Forestry College, Fujian Agriculture and Forestry University, Fuzhou, China
- Institute of Forestry Protection, Fujian Agriculture and Forestry University, Fuzhou, China
- * E-mail:
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Interactions between Melanin Enzymes and Their Atypical Recruitment to the Secretory Pathway by Palmitoylation. mBio 2016; 7:mBio.01925-16. [PMID: 27879337 PMCID: PMC5120144 DOI: 10.1128/mbio.01925-16] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Melanins are biopolymers that confer coloration and protection to the host organism against biotic or abiotic insults. The level of protection offered by melanin depends on its biosynthesis and its subcellular localization. Previously, we discovered that Aspergillus fumigatus compartmentalizes melanization in endosomes by recruiting all melanin enzymes to the secretory pathway. Surprisingly, although two laccases involved in the late steps of melanization are conventional secretory proteins, the four enzymes involved in the early steps of melanization lack a signal peptide or a transmembrane domain and are thus considered “atypical” secretory proteins. In this work, we found interactions among melanin enzymes and all melanin enzymes formed protein complexes. Surprisingly, the formation of protein complexes by melanin enzymes was not critical for their trafficking to the endosomal system. By palmitoylation profiling and biochemical analyses, we discovered that all four early melanin enzymes were strongly palmitoylated during conidiation. However, only the polyketide synthase (PKS) Alb1 was strongly palmitoylated during both vegetative hyphal growth and conidiation when constitutively expressed alone. This posttranslational lipid modification correlates the endosomal localization of all early melanin enzymes. Intriguingly, bioinformatic analyses predict that palmitoylation is a common mechanism for potential membrane association of polyketide synthases (PKSs) and nonribosomal peptide synthetases (NRPSs) in A. fumigatus. Our findings indicate that protein-protein interactions facilitate melanization by metabolic channeling, while posttranslational lipid modifications help recruit the atypical enzymes to the secretory pathway, which is critical for compartmentalization of secondary metabolism. Subcellular compartmentalization is increasingly recognized as an important aspect of fungal secondary metabolism. It facilitates sequential enzymatic reactions, provides mobility for enzymes and metabolites, and offers protection against self-toxification. However, how compartmentalization is achieved remains unclear given that the majority of enzymes encoded by secondary metabolism gene clusters are predicted to be cytosolic proteins. Through studying melanization in Aspergillus, we previously found that all enzymes involved in the early steps of melanization are atypical secretory proteins. Here, we discovered physical interactions among melanin enzymes. However, it was the posttranslational palmitoylation rather than the physical interaction that was responsible for their recruitment to the secretory pathway. Intriguingly, palmitoylation is likely a common mechanism for potential membrane association of polyketide synthases (PKSs) and nonribosomal peptide synthetases (NRPSs) in A. fumigatus. Collectively, our findings suggest that posttranslational lipid modification helps direct secondary metabolism to defined organelles for biosynthesis and trafficking.
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Kistler HC, Broz K. Cellular compartmentalization of secondary metabolism. Front Microbiol 2015; 6:68. [PMID: 25709603 PMCID: PMC4321598 DOI: 10.3389/fmicb.2015.00068] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 01/20/2015] [Indexed: 12/26/2022] Open
Abstract
Fungal secondary metabolism is often considered apart from the essential housekeeping functions of the cell. However, there are clear links between fundamental cellular metabolism and the biochemical pathways leading to secondary metabolite synthesis. Besides utilizing key biochemical precursors shared with the most essential processes of the cell (e.g., amino acids, acetyl CoA, NADPH), enzymes for secondary metabolite synthesis are compartmentalized at conserved subcellular sites that position pathway enzymes to use these common biochemical precursors. Co-compartmentalization of secondary metabolism pathway enzymes also may function to channel precursors, promote pathway efficiency and sequester pathway intermediates and products from the rest of the cell. In this review we discuss the compartmentalization of three well-studied fungal secondary metabolite biosynthetic pathways for penicillin G, aflatoxin and deoxynivalenol, and summarize evidence used to infer subcellular localization. We also discuss how these metabolites potentially are trafficked within the cell and may be exported.
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Affiliation(s)
- H. Corby Kistler
- United States Department of Agriculture-Agricultural Research Service, Cereal Disease Laboratory, University of MinnesotaSaint Paul, MN, USA
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Lim FY, Keller NP. Spatial and temporal control of fungal natural product synthesis. Nat Prod Rep 2014; 31:1277-86. [PMID: 25142354 PMCID: PMC4162804 DOI: 10.1039/c4np00083h] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Despite their oftentimes-elusive ecological role, fungal natural products have, for better or worse, impacted our daily lives tremendously owing to their diverse and potent bioactive properties. This Janus-faced nature of fungal natural products inevitably ushered in a field of research dedicated towards understanding the ecology, organisms, genes, enzymes, and biosynthetic pathways that give rise to this arsenal of diverse and complex chemistry. Ongoing research in fungal secondary metabolism has not only increased our appreciation for fungal natural products as an asset but also sheds light on the pivotal role that these once-regarded "metabolic wastes" play in fungal biology, defense, and stress response in addition to their potential contributions towards human mycoses. Full orchestration of secondary metabolism requires not only the seamless coordination between temporal and spatial control of SM-associated machineries (e.g. enzymes, cofactors, intermediates, and end-products) but also integration of these machineries into primary metabolic processes and established cellular mechanisms. An intriguing, but little known aspect of microbial natural product synthesis lies in the spatial organization of both pathway intermediates and enzymes responsible for the production of these compounds. In this highlight, we summarize some major breakthroughs in understanding the genes and regulation of fungal natural product synthesis and introduce the current state of knowledge on the spatial and temporal control of fungal natural product synthesis.
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Affiliation(s)
- Fang Yun Lim
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, U.S.A
| | - Nancy P. Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, U.S.A.,Corresponding author Professor Nancy P. Keller, Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, 1550 Linden Drive, Madison WI, U.S.A., Tel: (608)-262-9795; Fax: (608)-262-8418;
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Sequencing, physical organization and kinetic expression of the patulin biosynthetic gene cluster from Penicillium expansum. Int J Food Microbiol 2014; 189:51-60. [PMID: 25120234 DOI: 10.1016/j.ijfoodmicro.2014.07.028] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Revised: 07/11/2014] [Accepted: 07/22/2014] [Indexed: 01/19/2023]
Abstract
Patulin is a polyketide-derived mycotoxin produced by numerous filamentous fungi. Among them, Penicillium expansum is by far the most problematic species. This fungus is a destructive phytopathogen capable of growing on fruit, provoking the blue mold decay of apples and producing significant amounts of patulin. The biosynthetic pathway of this mycotoxin is chemically well-characterized, but its genetic bases remain largely unknown with only few characterized genes in less economic relevant species. The present study consisted of the identification and positional organization of the patulin gene cluster in P. expansum strain NRRL 35695. Several amplification reactions were performed with degenerative primers that were designed based on sequences from the orthologous genes available in other species. An improved genome Walking approach was used in order to sequence the remaining adjacent genes of the cluster. RACE-PCR was also carried out from mRNAs to determine the start and stop codons of the coding sequences. The patulin gene cluster in P. expansum consists of 15 genes in the following order: patH, patG, patF, patE, patD, patC, patB, patA, patM, patN, patO, patL, patI, patJ, and patK. These genes share 60-70% of identity with orthologous genes grouped differently, within a putative patulin cluster described in a non-producing strain of Aspergillus clavatus. The kinetics of patulin cluster genes expression was studied under patulin-permissive conditions (natural apple-based medium) and patulin-restrictive conditions (Eagle's minimal essential medium), and demonstrated a significant association between gene expression and patulin production. In conclusion, the sequence of the patulin cluster in P. expansum constitutes a key step for a better understanding of the mechanisms leading to patulin production in this fungus. It will allow the role of each gene to be elucidated, and help to define strategies to reduce patulin production in apple-based products.
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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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Affiliation(s)
| | | | - John E. Linz
- Department of Food Science and Human Nutrition,
- Department of Microbiology and Molecular Genetics,
- National Food Safety and Toxicology Center,
- Center for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824;
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Ehrlich K, Mack B, Cary J, Bhatnagar D, Kale S. A hypothesis to explain how LaeA specifically regulates certain secondary metabolite biosynthesis gene clusters. WORLD MYCOTOXIN J 2011. [DOI: 10.3920/wmj2010.1230] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Biosynthesis of mycotoxins involves transcriptional co-regulation of sets of clustered genes. We hypothesise that specific control of transcription of genes in these clusters by LaeA, a global regulator of secondary metabolite production and development in many filamentous fungi, results from its interaction with a Cys6Zn2 DNA-binding protein unique to the gene cluster.
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Affiliation(s)
- K. Ehrlich
- Southern Regional Research Center, ARS, USDA, 1100 Robert E. Lee Blvd, New Orleans, LA 70124, USA
| | - B. Mack
- Xavier University of Louisiana, 1 Drexel Drive, New Orleans, LA 70125, USA
| | - J. Cary
- Southern Regional Research Center, ARS, USDA, 1100 Robert E. Lee Blvd, New Orleans, LA 70124, USA
| | - D. Bhatnagar
- Southern Regional Research Center, ARS, USDA, 1100 Robert E. Lee Blvd, New Orleans, LA 70124, USA
| | - S. Kale
- Xavier University of Louisiana, 1 Drexel Drive, New Orleans, LA 70125, USA
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Roze LV, Chanda A, Linz JE. Compartmentalization and molecular traffic in secondary metabolism: a new understanding of established cellular processes. Fungal Genet Biol 2010; 48:35-48. [PMID: 20519149 DOI: 10.1016/j.fgb.2010.05.006] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 05/11/2010] [Accepted: 05/12/2010] [Indexed: 01/15/2023]
Abstract
Great progress has been made in understanding the regulation of expression of genes involved in secondary metabolism. Less is known about the mechanisms that govern the spatial distribution of the enzymes, cofactors, and substrates that mediate catalysis of secondary metabolites within the cell. Filamentous fungi in the genus Aspergillus synthesize an array of secondary metabolites and provide useful systems to analyze the mechanisms that mediate the temporal and spatial regulation of secondary metabolism in eukaryotes. For example, aflatoxin biosynthesis in Aspergillus parasiticus has been studied intensively because this mycotoxin is highly toxic, mutagenic, and carcinogenic in humans and animals. Using aflatoxin synthesis to illustrate key concepts, this review focuses on the mechanisms by which sub-cellular compartmentalization and intra-cellular molecular traffic contribute to the initiation and completion of secondary metabolism within the cell. We discuss the recent discovery of aflatoxisomes, specialized trafficking vesicles that participate in the compartmentalization of aflatoxin synthesis and export of the toxin to the cell exterior; this work provides a new and clearer understanding of how cells integrate secondary metabolism into basic cellular metabolism via the intra-cellular trafficking machinery.
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Affiliation(s)
- Ludmila V Roze
- Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI-48824, USA
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Abstract
Eukaryotes have evolved highly conserved vesicle transport machinery to deliver proteins to the vacuole. In this study we show that the filamentous fungus Aspergillus parasiticus employs this delivery system to perform new cellular functions, the synthesis, compartmentalization, and export of aflatoxin; this secondary metabolite is one of the most potent naturally occurring carcinogens known. Here we show that a highly pure vesicle-vacuole fraction isolated from A. parasiticus under aflatoxin-inducing conditions converts sterigmatocystin, a late intermediate in aflatoxin synthesis, to aflatoxin B(1); these organelles also compartmentalize aflatoxin. The role of vesicles in aflatoxin biosynthesis and export was confirmed by blocking vesicle-vacuole fusion using 2 independent approaches. Disruption of A. parasiticus vb1 (encodes a protein homolog of AvaA, a small GTPase known to regulate vesicle fusion in A. nidulans) or treatment with Sortin3 (blocks Vps16 function, one protein in the class C tethering complex) increased aflatoxin synthesis and export but did not affect aflatoxin gene expression, demonstrating that vesicles and not vacuoles are primarily involved in toxin synthesis and export. We also observed that development of aflatoxigenic vesicles (aflatoxisomes) is strongly enhanced under aflatoxin-inducing growth conditions. Coordination of aflatoxisome development with aflatoxin gene expression is at least in part mediated by Velvet (VeA), a global regulator of Aspergillus secondary metabolism. We propose a unique 2-branch model to illustrate the proposed role for VeA in regulation of aflatoxisome development and aflatoxin gene expression.
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Saikia S, Scott B. Functional analysis and subcellular localization of two geranylgeranyl diphosphate synthases from Penicillium paxilli. Mol Genet Genomics 2009; 282:257-71. [PMID: 19529962 PMCID: PMC2729982 DOI: 10.1007/s00438-009-0463-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Accepted: 05/28/2009] [Indexed: 10/26/2022]
Abstract
The filamentous fungus Penicillium paxilli contains two distinct geranylgeranyl diphosphate (GGPP) synthases, GgsA and GgsB (PaxG). PaxG and its homologues in Neotyphodium lolii and Fusarium fujikuroi are associated with diterpene secondary metabolite gene clusters. The genomes of other filamentous fungi including Aspergillus fumigatus, Aspergillus nidulans, Aspergillus niger, Aspergillus oryzae and Fusarium graminearum also contain two or more copies of GGPP synthase genes, although the diterpene metabolite capability of these fungi is not known. The objective of this study was to understand the biological significance of the presence of two copies of GGPP synthases in P. paxilli by investigating their subcellular localization. Using a carotenoid complementation assay and gene deletion analysis, we show that P. paxilli GgsA and PaxG have GGPP synthase activities and that paxG is required for paxilline biosynthesis, respectively. In the DeltapaxG mutant background ggsA was unable to complement paxilline biosynthesis. A GgsA-EGFP fusion protein was localized to punctuate organelles and the EGFP-GRV fusion protein, containing the C-terminus tripeptide GRV of PaxG, was localized to peroxisomes. A truncated PaxG mutant lacking the C-terminus tripeptide GRV was unable to complement a DeltapaxG mutant demonstrating that the tripeptide is functionally important for paxilline biosynthesis.
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Affiliation(s)
- Sanjay Saikia
- Institute of Molecular Biosciences, Massey University, Palmerston North, New Zealand.
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18
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Lubertozzi D, Keasling JD. Expression of a synthetic Artemesia annua amorphadiene synthase in Aspergillus nidulans yields altered product distribution. J Ind Microbiol Biotechnol 2008; 35:1191-8. [PMID: 18651187 DOI: 10.1007/s10295-008-0400-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Accepted: 07/08/2008] [Indexed: 01/20/2023]
Abstract
A gene encoding a plant terpene cyclase, Artemisia annua amorpha-4,11-diene synthase (ADS), was expressed in Aspergillus nidulans under control of a strong constitutive promoter, (p)gpdA. The transformants produced only small amounts of amorphadiene, but much larger amounts of similar sesquiterpenes normally produced as minor by-products in planta. In contrast, expression of ADS in Escherichia coli produced almost exclusively amorpha-4,11-diene. These results indicate that the host environment can greatly impact the terpenes produced from terpene synthases.
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Affiliation(s)
- David Lubertozzi
- Department of Chemical Engineering, University of California, Berkeley, CA 94720, USA
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Schwelm A, Barron NJ, Zhang S, Bradshaw RE. Early expression of aflatoxin-like dothistromin genes in the forest pathogen Dothistroma septosporum. ACTA ACUST UNITED AC 2007; 112:138-46. [PMID: 18262779 DOI: 10.1016/j.mycres.2007.03.018] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2007] [Revised: 02/22/2007] [Accepted: 03/20/2007] [Indexed: 11/30/2022]
Abstract
The forest pathogen Dothistroma septosporum produces the polyketide dothistromin, a mycotoxin very similar in structure to versicolorin B, a precursor of aflatoxin (AF). Dothistromin is a broad-range toxin and possibly involved in red-band needle blight disease. As the role of dothistromin in the disease is unknown the expression of dothistromin genes was studied to reveal clues to its function. Although the genes of AF and dothistromin biosynthesis are very similar, this study revealed remarkable differences in the timing of their expression. Secondary metabolites, like AF, are usually produced during late exponential phase. Previously identified dothistromin genes, as well as a newly reported versicolorin B synthase gene, vbsA, showed high levels of expression during the onset of exponential growth. This unusual early expression was also seen in transformants containing a green fluorescent protein (GFP) gene regulated by a dothistromin gene promoter, where the highest GFP expression occurred in young mycelium. Two hypotheses for the biological role of dothistromin are proposed based on these results. The study of dothistromin genes will improve current knowledge about secondary metabolite genes, their putative biological roles, and their regulation.
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Affiliation(s)
- Arne Schwelm
- National Centre for Advanced Bio-Protection Technologies, Institute of Molecular BioSciences, Massey University, Private Bag 11222, Palmerston North, New Zealand
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