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Hou X, Liu L, Xu D, Lai D, Zhou L. Involvement of LaeA and Velvet Proteins in Regulating the Production of Mycotoxins and Other Fungal Secondary Metabolites. J Fungi (Basel) 2024; 10:561. [PMID: 39194887 DOI: 10.3390/jof10080561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2024] [Revised: 07/30/2024] [Accepted: 08/06/2024] [Indexed: 08/29/2024] Open
Abstract
Fungi are rich sources of secondary metabolites of agrochemical, pharmaceutical, and food importance, such as mycotoxins, antibiotics, and antitumor agents. Secondary metabolites play vital roles in fungal pathogenesis, growth and development, oxidative status modulation, and adaptation/resistance to various environmental stresses. LaeA contains an S-adenosylmethionine binding site and displays methyltransferase activity. The members of velvet proteins include VeA, VelB, VelC, VelD and VosA for each member with a velvet domain. LaeA and velvet proteins can form multimeric complexes such as VosA-VelB and VelB-VeA-LaeA. They belong to global regulators and are mainly impacted by light. One of their most important functions is to regulate gene expressions that are responsible for secondary metabolite biosynthesis. The aim of this mini-review is to represent the newest cognition of the biosynthetic regulation of mycotoxins and other fungal secondary metabolites by LaeA and velvet proteins. In most cases, LaeA and velvet proteins positively regulate production of fungal secondary metabolites. The regulated fungal species mainly belong to the toxigenic fungi from the genera of Alternaria, Aspergillus, Botrytis, Fusarium, Magnaporthe, Monascus, and Penicillium for the production of mycotoxins. We can control secondary metabolite production to inhibit the production of harmful mycotoxins while promoting the production of useful metabolites by global regulation of LaeA and velvet proteins in fungi. Furthermore, the regulation by LaeA and velvet proteins should be a practical strategy in activating silent biosynthetic gene clusters (BGCs) in fungi to obtain previously undiscovered metabolites.
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Affiliation(s)
- Xuwen Hou
- MOA Key Lab of Pest Monitoring and Green Management, Department of Plant Pathology, College of Plant Protection, China Agricultural University, Beijing 100193, China
| | - Liyao Liu
- MOA Key Lab of Pest Monitoring and Green Management, Department of Plant Pathology, College of Plant Protection, China Agricultural University, Beijing 100193, China
| | - Dan Xu
- MOA Key Lab of Pest Monitoring and Green Management, Department of Plant Pathology, College of Plant Protection, China Agricultural University, Beijing 100193, China
| | - Daowan Lai
- MOA Key Lab of Pest Monitoring and Green Management, Department of Plant Pathology, College of Plant Protection, China Agricultural University, Beijing 100193, China
| | - Ligang Zhou
- MOA Key Lab of Pest Monitoring and Green Management, Department of Plant Pathology, College of Plant Protection, China Agricultural University, Beijing 100193, China
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Overexpression of global regulator LaeA increases secondary metabolite production in Monascus purpureus. Appl Microbiol Biotechnol 2020; 104:3049-3060. [DOI: 10.1007/s00253-020-10379-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 01/05/2020] [Accepted: 01/14/2020] [Indexed: 12/25/2022]
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Identification of a Classical Mutant in the Industrial Host Aspergillus niger by Systems Genetics: LaeA Is Required for Citric Acid Production and Regulates the Formation of Some Secondary Metabolites. G3-GENES GENOMES GENETICS 2015; 6:193-204. [PMID: 26566947 PMCID: PMC4704718 DOI: 10.1534/g3.115.024067] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The asexual filamentous fungus Aspergillus niger is an important industrial cell factory for citric acid production. In this study, we genetically characterized a UV-generated A. niger mutant that was originally isolated as a nonacidifying mutant, which is a desirable trait for industrial enzyme production. Physiological analysis showed that this mutant did not secrete large amounts of citric acid and oxalic acid, thus explaining the nonacidifying phenotype. As traditional complementation approaches to characterize the mutant genotype were unsuccessful, we used bulk segregant analysis in combination with high-throughput genome sequencing to identify the mutation responsible for the nonacidifying phenotype. Since A. niger has no sexual cycle, parasexual genetics was used to generate haploid segregants derived from diploids by loss of whole chromosomes. We found that the nonacidifying phenotype was caused by a point mutation in the laeA gene. LaeA encodes a putative methyltransferase-domain protein, which we show here to be required for citric acid production in an A. niger lab strain (N402) and in other citric acid production strains. The unexpected link between LaeA and citric acid production could provide new insights into the transcriptional control mechanisms related to citric acid production in A. niger. Interestingly, the secondary metabolite profile of a ΔlaeA strain differed from the wild-type strain, showing both decreased and increased metabolite levels, indicating that LaeA is also involved in regulating the production of secondary metabolites. Finally, we show that our systems genetics approach is a powerful tool to identify trait mutations.
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Abstract
Mycotoxins are natural contaminants of food and feed products, posing a substantial health risk to humans and animals throughout the world. A plethora of filamentous fungi has been identified as mycotoxin producers and most of these fungal species belong to the genera Aspergillus, Fusarium, and Penicillium. A number of studies have been conducted to better understand the molecular mechanisms of biosynthesis of key mycotoxins and the regulatory cascades controlling toxigenesis. In many cases, the mycotoxin biosynthetic genes are clustered and regulated by one or more pathway-specific transcription factor(s). In addition, as biosynthesis of many secondary metabolites is coordinated with fungal growth and development, there are a number of upstream regulators affecting biosynthesis of mycotoxins in fungi. This review presents a concise summary of the regulation of mycotoxin biosynthesis, focusing on the roles of the upstream regulatory elements governing biosynthesis of aflatoxin and sterigmatocystin in Aspergillus.
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Affiliation(s)
| | - Jae-Hyuk Yu
- University of Wisconsin-Madison, Madison, Wisconsin, USA
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Houbraken J, de Vries RP, Samson RA. Modern taxonomy of biotechnologically important Aspergillus and Penicillium species. ADVANCES IN APPLIED MICROBIOLOGY 2014; 86:199-249. [PMID: 24377856 DOI: 10.1016/b978-0-12-800262-9.00004-4] [Citation(s) in RCA: 139] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Taxonomy is a dynamic discipline and name changes of fungi with biotechnological, industrial, or medical importance are often difficult to understand for researchers in the applied field. Species belonging to the genera Aspergillus and Penicillium are commonly used or isolated, and inadequate taxonomy or uncertain nomenclature of these genera can therefore lead to tremendous confusion. Misidentification of strains used in biotechnology can be traced back to (1) recent changes in nomenclature, (2) new taxonomic insights, including description of new species, and/or (3) incorrect identifications. Changes in the recent published International Code of Nomenclature for Algae, Fungi and Plants will lead to numerous name changes of existing Aspergillus and Penicillium species and an overview of the current names of biotechnological important species is given. Furthermore, in (biotechnological) literature old and invalid names are still used, such as Aspergillus awamori, A. foetidus, A. kawachii, Talaromyces emersonii, Acremonium cellulolyticus, and Penicillium funiculosum. An overview of these and other species with their correct names is presented. Furthermore, the biotechnologically important species Talaromyces thermophilus is here combined in Thermomyces as Th. dupontii. The importance of Aspergillus, Penicillium, and related genera is also illustrated by the high number of undertaken genome sequencing projects. A number of these strains are incorrectly identified or atypical strains are selected for these projects. Recommendations for correct strain selection are given here. Phylogenetic analysis shows a close relationship between the genome-sequenced strains of Aspergillus, Penicillium, and Monascus. Talaromyces stipitatus and T. marneffei (syn. Penicillium marneffei) are closely related to Thermomyces lanuginosus and Th. dupontii (syn. Talaromyces thermophilus), and these species appear to be distantly related to Aspergillus and Penicillium. In the last part of this review, an overview of heterothallic reproduction in Aspergillus and Penicillium is given. The new insights in the taxonomy of Aspergillus, Penicillium, and related genera will help to interpret the results generated with comparative genomics studies or other studies dealing with evolution of, for example, enzymes, mating-type loci, virulence genes, and secondary metabolite biosynthetic gene clusters.
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Affiliation(s)
- Jos Houbraken
- CBS-KNAW Fungal Biodiversity Centre, Utrecht, The Netherlands.
| | | | - Robert A Samson
- CBS-KNAW Fungal Biodiversity Centre, Utrecht, The Netherlands
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Leitão AL, Enguita FJ. Fungal extrolites as a new source for therapeutic compounds and as building blocks for applications in synthetic biology. Microbiol Res 2014; 169:652-65. [PMID: 24636745 DOI: 10.1016/j.micres.2014.02.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 02/15/2014] [Accepted: 02/16/2014] [Indexed: 01/07/2023]
Abstract
Secondary metabolic pathways of fungal origin provide an almost unlimited resource of new compounds for medical applications, which can fulfill some of the, currently unmet, needs for therapeutic alternatives for the treatment of a number of diseases. Secondary metabolites secreted to the extracellular medium (extrolites) belong to diverse chemical and structural families, but the majority of them are synthesized by the condensation of a limited number of precursor building blocks including amino acids, sugars, lipids and low molecular weight compounds also employed in anabolic processes. In fungi, genes related to secondary metabolic pathways are frequently clustered together and show a modular organization within fungal genomes. The majority of fungal gene clusters responsible for the biosynthesis of secondary metabolites contain genes encoding a high molecular weight condensing enzyme which is responsible for the assembly of the precursor units of the metabolite. They also contain other auxiliary genes which encode enzymes involved in subsequent chemical modification of the metabolite core. Synthetic biology is a branch of molecular biology whose main objective is the manipulation of cellular components and processes in order to perform logically connected metabolic functions. In synthetic biology applications, biosynthetic modules from secondary metabolic processes can be rationally engineered and combined to produce either new compounds, or to improve the activities and/or the bioavailability of the already known ones. Recently, advanced genome editing techniques based on guided DNA endonucleases have shown potential for the manipulation of eukaryotic and bacterial genomes. This review discusses the potential application of genetic engineering and genome editing tools in the rational design of fungal secondary metabolite pathways by taking advantage of the increasing availability of genomic and biochemical data.
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Affiliation(s)
- Ana Lúcia Leitão
- Departamento de Ciências e Tecnologia da Biomassa, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus da Caparica, Caparica 2829-516, Portugal.
| | - Francisco J Enguita
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Av. Prof. Egas Moniz, Lisboa 1649-028, Portugal.
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The bZIP protein MeaB mediates virulence attributes in Aspergillus flavus. PLoS One 2013; 8:e74030. [PMID: 24040154 PMCID: PMC3767667 DOI: 10.1371/journal.pone.0074030] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Accepted: 08/01/2013] [Indexed: 11/19/2022] Open
Abstract
LaeA is a fungal specific virulence factor of both plant and human pathogenic fungi. Transcriptional profiles of laeA mutants have been successfully exploited to identify regulatory mechanisms of secondary metabolism in fungi; here we use laeA mutants as tools to elucidate virulence attributes in Aspergillus flavus. Microarray expression profiles of ΔlaeA and over-expression laeA (OE::laeA) were compared to wild type A. flavus. Strikingly, several nitrogen metabolism genes are oppositely mis-regulated in the ΔlaeA and OE::laeA mutants. One of the nitrogen regulatory genes, the bZIP encoding meaB, is up-regulated in ΔlaeA. Significantly, over-expression of meaB (OE::meaB) phenocopies the decreased virulence attributes of a ΔlaeA phenotype including decreased colonization of host seed, reduced lipase activity and loss of aflatoxin B1 production in seed. However, a double knock-down of laeA and meaB (KD::laeA,meaB) demonstrated that KD::laeA,meaB closely resembled ΔlaeA rather than wild type or ΔmeaB in growth, aflatoxin biosynthesis and sclerotia production thus suggesting that meaB does not contribute to the ΔlaeA phenotype. MeaB and LaeA appear to be part of regulatory networks that allow them to have both shared and distinct roles in fungal biology.
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Sanchez JF, Somoza AD, Keller NP, Wang CCC. Advances in Aspergillus secondary metabolite research in the post-genomic era. Nat Prod Rep 2012; 29:351-71. [PMID: 22228366 DOI: 10.1039/c2np00084a] [Citation(s) in RCA: 194] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This review studies the impact of whole genome sequencing on Aspergillus secondary metabolite research. There has been a proliferation of many new, intriguing discoveries since sequencing data became widely available. What is more, the genomes disclosed the surprising finding that there are many more secondary metabolite biosynthetic pathways than laboratory research had suggested. Activating these pathways has been met with some success, but many more dormant genes remain to be awakened.
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Affiliation(s)
- James F Sanchez
- University of Southern California-Pharmacology and Pharmaceutical Sciences, Los Angeles, California 90033, USA
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Lim FY, Sanchez JF, Wang CC, Keller NP. Toward awakening cryptic secondary metabolite gene clusters in filamentous fungi. Methods Enzymol 2012; 517:303-24. [PMID: 23084945 PMCID: PMC3703436 DOI: 10.1016/b978-0-12-404634-4.00015-2] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Mining for novel natural compounds is of eminent importance owing to the continuous need for new pharmaceuticals. Filamentous fungi are historically known to harbor the genetic capacity for an arsenal of natural compounds, both beneficial and detrimental to humans. The majority of these metabolites are still cryptic or silent under standard laboratory culture conditions. Mining for these cryptic natural products can be an excellent source for identifying new compound classes. Capitalizing on the current knowledge on how secondary metabolite gene clusters are regulated has allowed the research community to unlock many hidden fungal treasures, as described in this chapter.
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Affiliation(s)
- Fang Yun Lim
- Department of Medical Microbiology and Immunology, University of Wisconsin, Madison, Wisconsin, USA
| | - James F. Sanchez
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, School of Pharmacy, Los Angeles, California, USA
| | - Clay C.C. Wang
- Department of Pharmacology and Pharmaceutical Sciences, University of Southern California, School of Pharmacy, Los Angeles, California, USA,Department of Chemistry, University of Southern California, College of Letters, Arts, and Sciences, Los Angeles, California, USA
| | - Nancy P. Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin, Madison, Wisconsin, USA,Corresponding author:
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Gacek A, Strauss J. The chromatin code of fungal secondary metabolite gene clusters. Appl Microbiol Biotechnol 2012; 95:1389-404. [PMID: 22814413 PMCID: PMC3427479 DOI: 10.1007/s00253-012-4208-8] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 05/24/2012] [Accepted: 05/24/2012] [Indexed: 01/07/2023]
Abstract
Secondary metabolite biosynthesis genes in fungi are usually physically linked and organized in large gene clusters. The physical linkage of genes involved in the same biosynthetic pathway minimizes the amount of regulatory steps necessary to regulate the biosynthetic machinery and thereby contributes to physiological economization. Regulation by chromatin accessibility is a proficient molecular mechanism to synchronize transcriptional activity of large genomic regions. Chromatin regulation largely depends on DNA and histone modifications and the histone code hypothesis proposes that a certain combination of modifications, such as acetylation, methylation or phosphorylation, is needed to perform a specific task. A number of reports from several laboratories recently demonstrated that fungal secondary metabolite (SM) biosynthesis clusters are controlled by chromatin-based mechanisms and histone acetyltransferases, deacetylases, methyltransferases, and proteins involved in heterochromatin formation were found to be involved. This led to the proposal that establishment of repressive chromatin domains over fungal SM clusters under primary metabolic conditions is a conserved mechanism that prevents SM production during the active growth phase. Consequently, transcriptional activation of SM clusters requires reprogramming of the chromatin landscape and replacement of repressive histone marks by activating marks. This review summarizes recent advances in our understanding of chromatin-based SM cluster regulation and highlights some of the open questions that remain to be answered before we can draw a more comprehensive picture.
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Affiliation(s)
- Agnieszka Gacek
- Fungal Genetics and Genomics Unit, Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Science, University and Research Center—Campus Tulln, 3430 Tulln/Donau, Austria
| | - Joseph Strauss
- Fungal Genetics and Genomics Unit, Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Science, University and Research Center—Campus Tulln, 3430 Tulln/Donau, Austria ,Health and Environment Department, Austrian Institute of Technology, University and Research Center—Campus Tulln, 3430 Tulln/Donau, Austria
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Yin W, Keller NP. Transcriptional regulatory elements in fungal secondary metabolism. J Microbiol 2011; 49:329-39. [PMID: 21717315 DOI: 10.1007/s12275-011-1009-1] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Accepted: 03/15/2011] [Indexed: 01/19/2023]
Abstract
Filamentous fungi produce a variety of secondary metabolites of diverse beneficial and detrimental activities to humankind. The genes required for a given secondary metabolite are typically arranged in a gene cluster. There is considerable evidence that secondary metabolite gene regulation is, in part, by transcriptional control through hierarchical levels of transcriptional regulatory elements involved in secondary metabolite cluster regulation. Identification of elements regulating secondary metabolism could potentially provide a means of increasing production of beneficial metabolites, decreasing production of detrimental metabolites, aid in the identification of 'silent' natural products and also contribute to a broader understanding of molecular mechanisms by which secondary metabolites are produced. This review summarizes regulation of secondary metabolism associated with transcriptional regulatory elements from a broad view as well as the tremendous advances in discovery of cryptic or novel secondary metabolites by genomic mining.
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Affiliation(s)
- Wenbing Yin
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706, USA
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13
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Abstract
Aspergillus flavus is saprophytic soil fungus that infects and contaminates preharvest and postharvest seed crops with the carcinogenic secondary metabolite aflatoxin. The fungus is also an opportunistic animal and human pathogen causing aspergillosis diseases with incidence increasing in the immunocompromised population. Whole genome sequences of A. flavus have been released and reveal 55 secondary metabolite clusters that are regulated by different environmental regimes and the global secondary metabolite regulators LaeA and VeA. Characteristics of A. flavus associated with pathogenicity and niche specialization include secondary metabolite production, enzyme elaboration, and a sophisticated oxylipin host crosstalk associated with a quorum-like development program. One of the more promising strategies in field control involves the use of atoxic strains of A. flavus in competitive exclusion studies. In this review, we discuss A. flavus as an agricultural and medical threat and summarize recent research advances in genomics, elucidation of parameters of pathogenicity, and control measures.
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Affiliation(s)
- Saori Amaike
- Department of Plant Pathology, University of Wisconsin, Madison, Wisconsin 53706, USA
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