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Rousta N, Aslan M, Yesilcimen Akbas M, Ozcan F, Sar T, Taherzadeh MJ. Effects of fungal based bioactive compounds on human health: Review paper. Crit Rev Food Sci Nutr 2023; 64:7004-7027. [PMID: 36794421 DOI: 10.1080/10408398.2023.2178379] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Since the first years of history, microbial fermentation products such as bread, wine, yogurt and vinegar have always been noteworthy regarding their nutritional and health effects. Similarly, mushrooms have been a valuable food product in point of both nutrition and medicine due to their rich chemical components. Alternatively, filamentous fungi, which can be easier to produce, play an active role in the synthesis of some bioactive compounds, which are also important for health, as well as being rich in protein content. Therefore, this review presents some important bioactive compounds (bioactive peptides, chitin/chitosan, β-glucan, gamma-aminobutyric acid, L-carnitine, ergosterol and fructooligosaccharides) synthesized by fungal strains and their health benefits. In addition, potential probiotic- and prebiotic fungi were researched to determine their effects on gut microbiota. The current uses of fungal based bioactive compounds for cancer treatment were also discussed. The use of fungal strains in the food industry, especially to develop innovative food production, has been seen as promising microorganisms in obtaining healthy and nutritious food.
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Affiliation(s)
- Neda Rousta
- Swedish Centre for Resource Recovery, University of Borås, Borås, Sweden
| | - Melissa Aslan
- Swedish Centre for Resource Recovery, University of Borås, Borås, Sweden
- Department of Molecular Biology and Genetics, Gebze Technical University, Gebze-Kocaeli, Turkey
| | - Meltem Yesilcimen Akbas
- Department of Molecular Biology and Genetics, Gebze Technical University, Gebze-Kocaeli, Turkey
| | - Ferruh Ozcan
- Department of Molecular Biology and Genetics, Gebze Technical University, Gebze-Kocaeli, Turkey
| | - Taner Sar
- Swedish Centre for Resource Recovery, University of Borås, Borås, Sweden
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Xia H, Noushahi HA, Khan AH, Liu Y, Cosoveanu A, Cui L, Tang J, Iqbal S, Shu S. Genome sequencing of Colletotrichum gloeosporioides ESO026 reveals plausible pathway of HupA. Mol Biol Rep 2022; 49:11611-11622. [PMID: 36161578 DOI: 10.1007/s11033-022-07850-y] [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: 04/04/2022] [Revised: 06/23/2022] [Accepted: 08/08/2022] [Indexed: 11/26/2022]
Abstract
BACKGROUND Colletotrichum gloeosporioides ES026, isolated as an endophytic fungal strain, was found to produce the important medicinal compound HuperzineA (HupA). In a genetic context, ES026 showed potential in elucidating the biosynthetic pathway of HupA. METHODS AND RESULTS The ES026 strain was sequenced using de-novo Illumina sequencing methods in this study. Assembling the cleaned data resulted in 58,594,804bp, consisting of 404 scaffolds. The G + C mol % content of this genome was 52.53%. The genome progressive-alignment with other 4 Colletotrichum strains revealed that ES026 showed closer relation with 030206, SMCG1#C and Nara gc5. More than 60 putative biosynthetic clusters were predicted with the fungal version antiSMASH4.0 program. More than 33 types I polyketide-related biosynthetic gene clusters were distributed, containing PKS and PKS-NRPS (polyketide-nonribosomal peptides) hybrid gene clusters. Another 8 NRPS biosynthetic gene clusters were distributed among the genome of ES026. The prenyltransferases, probably involved in aromatic prenyl-compounds and terpenoid biosynthesis, were analyzed using bioinformatics tools like MEGA. CONCLUSION We predicted a new possible biosynthetic pathway for the HupA from the pipecolic acid, based on the published HupA biosynthesis proposed pathway, the biosynthesis and pipecolic acid-derived compounds. We hypothesize that a hybrid PKS-NRPS mega-enzyme was probably involved in the biosynthesis of HupA with the pipecolic acid, the building block of rapamycin, as a HupA precursor. The rapamycin is produced from a polyketide biosynthesis pathway, and the domain incorporating the pipecolic acid is studied.
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Affiliation(s)
- Haiyang Xia
- College of Plant Science and Technology, Huazhong Agricultural University, 430070, Wuhan, China
- Bio-Pharmaceuticals Institute , Taizhou University, 317000, Taizhou, China
| | - Hamza Armghan Noushahi
- College of Plant Science and Technology, Huazhong Agricultural University, 430070, Wuhan, China
| | - Aamir Hamid Khan
- National Key Laboratory of Crop Genetics Improvement, Huazhong Agricultural University, 430070, Wuhan, China
| | - Ying Liu
- College of Plant Science and Technology, Huazhong Agricultural University, 430070, Wuhan, China
| | - Andreea Cosoveanu
- Department of Botany, Ecology & Plant Physiology, CIPEV Group, Faculty of Science, Biology Section, Universidad de La Laguna, 38206, San Cristobal de La Laguna, Tenerife, Spain
| | - Lingli Cui
- College of Plant Science and Technology, Huazhong Agricultural University, 430070, Wuhan, China
| | - Jing Tang
- College of Plant Science and Technology, Huazhong Agricultural University, 430070, Wuhan, China
| | - Shehzad Iqbal
- Faculty of Agricultural Sciences, University of Talca, 3460000, Talca, Chile
| | - Shaohua Shu
- College of Plant Science and Technology, Huazhong Agricultural University, 430070, Wuhan, China.
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Villarino M, Rodríguez-Pires S, Requena E, Melgarejo P, De Cal A, Espeso EA. A Secondary Metabolism Pathway Involved in the Production of a Putative Toxin Is Expressed at Early Stage of Monilinia laxa Infection. FRONTIERS IN PLANT SCIENCE 2022; 13:818483. [PMID: 35401637 PMCID: PMC8988988 DOI: 10.3389/fpls.2022.818483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 01/24/2022] [Indexed: 06/14/2023]
Abstract
The necrotrophic pathogenic fungus Monilinia laxa causes brown rot disease on stone fruit generating significant yield losses. So far, a limited number of pathogenesis-related virulence factors, such as cell wall degrading enzymes and potential phytotoxins, have been described in Monilinia spp. Using RNA-sequencing data from highly virulent M. laxa ML8L strain at early stages of the infection process (6, 14, 24, and 48 h post-inoculation, hpi) on nectarine and the Pathogen-Host-Interactions (PHI) database, we selected a number of genes for further study and ranked them according to their transcription levels. We identified a class of genes highly expressed at 6 hpi and that their expression decreased to almost undetectable levels at 14 to 48 hpi. Among these genes we found Monilinia__061040 encoding a non-ribosomal peptide synthase (NRPS). Monilinia__061040 together with other five co-regulated genes, forms a secondary metabolism cluster potentially involved in the production of epipolythiodioxopiperazine (ETP) toxin. Quantitative-PCR data confirmed previous RNA sequencing results from the virulent ML8L strain. Interestingly, in a less virulent M. laxa ML5L strain the expression levels of this pathway were reduced compared to the ML8L strain during nectarine infection. In vitro experiments showed that liquid medium containing peach extract mimicked the results observed using nectarines. In fact, upregulation of the NRPS coding gene was also observed in minimal medium suggesting the existence of a fruit-independent mechanism of regulation for this putative toxin biosynthetic pathway that is also downregulated in the less virulent strain. These results emphasize the role of this secondary metabolism pathway during the early stage of brown rot disease development and show alternative models to study the induction of virulence genes in this fungus.
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Affiliation(s)
- Maria Villarino
- Grupo Hongos Fitopatógenos, Departamento de Protección Vegetal, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (Consejo Superior de Investigaciones Científicas), Madrid, Spain
| | - Silvia Rodríguez-Pires
- Laboratorio de Biología Celular de Aspergillus, Departamento de Biología Celular y Molecular, Centro de Investigaciones Biológicas Margarita Salas-Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Elena Requena
- Grupo Hongos Fitopatógenos, Departamento de Protección Vegetal, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (Consejo Superior de Investigaciones Científicas), Madrid, Spain
| | - Paloma Melgarejo
- Dirección General de Producciones y Mercados Agrarios, Ministerio de Agricultura, Pesca y Alimentación, Madrid, Spain
| | - Antonieta De Cal
- Grupo Hongos Fitopatógenos, Departamento de Protección Vegetal, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (Consejo Superior de Investigaciones Científicas), Madrid, Spain
| | - Eduardo A. Espeso
- Laboratorio de Biología Celular de Aspergillus, Departamento de Biología Celular y Molecular, Centro de Investigaciones Biológicas Margarita Salas-Consejo Superior de Investigaciones Científicas, Madrid, Spain
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Shokrollahi N, Ho CL, Zainudin NAIM, Wahab MABA, Wong MY. Identification of non-ribosomal peptide synthetase in Ganoderma boninense Pat. that was expressed during the interaction with oil palm. Sci Rep 2021; 11:16330. [PMID: 34381084 PMCID: PMC8358039 DOI: 10.1038/s41598-021-95549-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Accepted: 07/16/2021] [Indexed: 02/07/2023] Open
Abstract
Basal stem rot (BSR) of oil palm is a disastrous disease caused by a white-rot fungus Ganoderma boninense Pat. Non-ribosomal peptides (NRPs) synthesized by non-ribosomal peptide synthetases (NRPSs) are a group of secondary metabolites that act as fungal virulent factors during pathogenesis in the host. In this study, we aimed to isolate NRPS gene of G. boninense strain UPMGB001 and investigate the role of this gene during G. boninense-oil palm interaction. The isolated NRPS DNA fragment of 8322 bp was used to predict the putative peptide sequence of different domains and showed similarity with G. sinense (85%) at conserved motifs of three main NRPS domains. Phylogenetic analysis of NRPS peptide sequences demonstrated that NRPS of G. boninense belongs to the type VI siderophore family. The roots of 6-month-old oil palm seedlings were artificially inoculated for studying NRPS gene expression and disease severity in the greenhouse. The correlation between high disease severity (50%) and high expression (67-fold) of G. boninense NRPS gene at 4 months after inoculation and above indicated that this gene played a significant role in the advancement of BSR disease. Overall, these findings increase our knowledge on the gene structure of NRPS in G. boninense and its involvement in BSR pathogenesis as an effector gene.
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Affiliation(s)
- Neda Shokrollahi
- grid.11142.370000 0001 2231 800XDepartment of Plant Protection, Faculty of Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor Malaysia
| | - Chai-Ling Ho
- grid.11142.370000 0001 2231 800XDepartment of Cell and Molecular Biology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, 43400 Serdang, Selangor Malaysia
| | - Nur Ain Izzati Mohd Zainudin
- grid.11142.370000 0001 2231 800XDepartment of Biology, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor Malaysia
| | - Mohd As’wad Bin Abul Wahab
- grid.11142.370000 0001 2231 800XDepartment of Plant Protection, Faculty of Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor Malaysia
| | - Mui-Yun Wong
- grid.11142.370000 0001 2231 800XDepartment of Plant Protection, Faculty of Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor Malaysia ,grid.11142.370000 0001 2231 800XInstitute of Plantation Studies, Universiti Putra Malaysia, 43400 Serdang, Selangor Malaysia
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Shi JC, Shi WL, Zhou YR, Chen XL, Zhang YZ, Zhang X, Zhang WX, Song XY. The Putative Methyltransferase TlLAE1 Is Involved in the Regulation of Peptaibols Production in the Biocontrol Fungus Trichoderma longibrachiatum SMF2. Front Microbiol 2020; 11:1267. [PMID: 32612590 PMCID: PMC7307461 DOI: 10.3389/fmicb.2020.01267] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2020] [Accepted: 05/18/2020] [Indexed: 11/30/2022] Open
Abstract
The biocontrol fungus Trichoderma longibrachiatum SMF2 secretes a large quantity of peptaibols that have been shown to have a range of biological activities and therefore great application values. However, the mechanism of the regulatory expression of peptaibols is still unclear. The putative methyltransferase LaeA/LAE1 is a global regulator involved in the biosynthesis of some secondary metabolites in filamentous fungi. In this study, we demonstrated that the ortholog of LaeA/LAE1 in the biocontrol fungus T. longibrachiatum SMF2, TlLAE1, plays an important role in the regulation of peptaibols production. Deletion of Tllae1 resulted in a slight negative impact on mycelial growth, and a significant defect in conidial production. Deletion of Tllae1 also compromised the production of peptaibols to a large degree. Further analyses indicated that this defect occurred at the transcriptional level of the two synthetases-encoding genes, tlx1 and tlx2, which are responsible for peptaibols production. By contrast, constitutive expression of Tllae1 in T. longibrachiatum SMF2 led to 2-fold increased peptaibols production, suggesting that this is a strategy to improve peptaibols production in Trichoderma fungi. These results demonstrate the important role of LAE1 in the regulation of peptaibols production in T. longibrachiatum SMF2.
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Affiliation(s)
- Jin-Chao Shi
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China
| | - Wei-Ling Shi
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China
| | - Yan-Rong Zhou
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China
| | - Xiu-Lan Chen
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China
| | - Yu-Zhong Zhang
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.,College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Xia Zhang
- Department of Molecular Biology, Qingdao Vland Biotech Inc., Qingdao, China
| | - Wei-Xin Zhang
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China
| | - Xiao-Yan Song
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China
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Calla-Quispe E, Fuentes-Rivera HL, Ramírez P, Martel C, Ibañez AJ. Mass Spectrometry: A Rosetta Stone to Learn How Fungi Interact and Talk. Life (Basel) 2020; 10:E89. [PMID: 32575729 PMCID: PMC7345136 DOI: 10.3390/life10060089] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2020] [Revised: 06/16/2020] [Accepted: 06/18/2020] [Indexed: 01/08/2023] Open
Abstract
Fungi are a highly diverse group of heterotrophic organisms that play an important role in diverse ecological interactions, many of which are chemically mediated. Fungi have a very versatile metabolism, which allows them to synthesize a large number of still little-known chemical compounds, such as soluble compounds that are secreted into the medium and volatile compounds that are chemical mediators over short and long distances. Mass spectrometry (MS) is currently playing a dominant role in mycological studies, mainly due to its inherent sensitivity and rapid identification capabilities of different metabolites. Furthermore, MS has also been used as a reliable and accurate tool for fungi identification (i.e., biotyping). Here, we introduce the readers about fungal specialized metabolites, their role in ecological interactions and provide an overview on the MS-based techniques used in fungal studies. We particularly present the importance of sampling techniques, strategies to reduce false-positive identification and new MS-based analytical strategies that can be used in mycological studies, further expanding the use of MS in broader applications. Therefore, we foresee a bright future for mass spectrometry-based research in the field of mycology.
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Affiliation(s)
- Erika Calla-Quispe
- Instituto de Ciencias Ómicas y Biotecnología Aplicada (ICOBA), Pontificia Universidad Católica del Perú (PUCP), Av. Universitaria 1801, San Miguel 15088, Lima, Peru; (E.C.-Q.); (H.L.F.-R.); (C.M.)
| | - Hammerly Lino Fuentes-Rivera
- Instituto de Ciencias Ómicas y Biotecnología Aplicada (ICOBA), Pontificia Universidad Católica del Perú (PUCP), Av. Universitaria 1801, San Miguel 15088, Lima, Peru; (E.C.-Q.); (H.L.F.-R.); (C.M.)
- Laboratory of Molecular Microbiology and Biotechnology, Faculty of Biological Sciences, Universidad Nacional Mayor de San Marcos (UNMSM), Av. Germán Amézaga 375, Lima 15081, Peru;
| | - Pablo Ramírez
- Laboratory of Molecular Microbiology and Biotechnology, Faculty of Biological Sciences, Universidad Nacional Mayor de San Marcos (UNMSM), Av. Germán Amézaga 375, Lima 15081, Peru;
| | - Carlos Martel
- Instituto de Ciencias Ómicas y Biotecnología Aplicada (ICOBA), Pontificia Universidad Católica del Perú (PUCP), Av. Universitaria 1801, San Miguel 15088, Lima, Peru; (E.C.-Q.); (H.L.F.-R.); (C.M.)
- Museo de Historia Natural, Universidad Nacional Mayor de San Marcos (UNMSM), Av. Arenales 1256, Jesús María 15072, Lima, Peru
| | - Alfredo J. Ibañez
- Instituto de Ciencias Ómicas y Biotecnología Aplicada (ICOBA), Pontificia Universidad Católica del Perú (PUCP), Av. Universitaria 1801, San Miguel 15088, Lima, Peru; (E.C.-Q.); (H.L.F.-R.); (C.M.)
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7
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Villena GK, Kitazono AA, Hernández-Macedo M L. Bioengineering Fungi and Yeast for the Production of Enzymes, Metabolites, and Value-Added Compounds. Fungal Biol 2020. [DOI: 10.1007/978-3-030-41870-0_9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Hautbergue T, Jamin EL, Debrauwer L, Puel O, Oswald IP. From genomics to metabolomics, moving toward an integrated strategy for the discovery of fungal secondary metabolites. Nat Prod Rep 2019; 35:147-173. [PMID: 29384544 DOI: 10.1039/c7np00032d] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Fungal secondary metabolites are defined by bioactive properties that ensure adaptation of the fungus to its environment. Although some of these natural products are promising sources of new lead compounds especially for the pharmaceutical industry, others pose risks to human and animal health. The identification of secondary metabolites is critical to assessing both the utility and risks of these compounds. Since fungi present biological specificities different from other microorganisms, this review covers the different strategies specifically used in fungal studies to perform this critical identification. Strategies focused on the direct detection of the secondary metabolites are firstly reported. Particularly, advances in high-throughput untargeted metabolomics have led to the generation of large datasets whose exploitation and interpretation generally require bioinformatics tools. Then, the genome-based methods used to study the entire fungal metabolic potential are reported. Transcriptomic and proteomic tools used in the discovery of fungal secondary metabolites are presented as links between genomic methods and metabolomic experiments. Finally, the influence of the culture environment on the synthesis of secondary metabolites by fungi is highlighted as a major factor to consider in research on fungal secondary metabolites. Through this review, we seek to emphasize that the discovery of natural products should integrate all of these valuable tools. Attention is also drawn to emerging technologies that will certainly revolutionize fungal research and to the use of computational tools that are necessary but whose results should be interpreted carefully.
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Affiliation(s)
- T Hautbergue
- Toxalim (Research Centre in Food Toxicology) Université de Toulouse, INRA, ENVT, INP-Purpan, UPS, F-31027 Toulouse, France.
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Distribution and Evolution of Nonribosomal Peptide Synthetase Gene Clusters in the Ceratocystidaceae. Genes (Basel) 2019; 10:genes10050328. [PMID: 31052158 PMCID: PMC6563098 DOI: 10.3390/genes10050328] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 03/29/2019] [Accepted: 04/01/2019] [Indexed: 01/07/2023] Open
Abstract
In filamentous fungi, genes in secondary metabolite biosynthetic pathways are generally clustered. In the case of those pathways involved in nonribosomal peptide production, a nonribosomal peptide synthetase (NRPS) gene is commonly found as a main element of the cluster. Large multifunctional enzymes are encoded by members of this gene family that produce a broad spectrum of bioactive compounds. In this research, we applied genome-based identification of nonribosomal peptide biosynthetic gene clusters in the family Ceratocystidaceae. For this purpose, we used the whole genome sequences of species from the genera Ceratocystis,Davidsoniella,Thielaviopsis, Endoconidiophora,Bretziella, Huntiella, and Ambrosiella. To identify and characterize the clusters, different bioinformatics and phylogenetic approaches, as well as PCR-based methods were used. In all genomes studied, two highly conserved NRPS genes (one monomodular and one multimodular) were identified and their potential products were predicted to be siderophores. Expression analysis of two Huntiella species (H. moniliformis and H. omanensis) confirmed the accuracy of the annotations and proved that the genes in both clusters are expressed. Furthermore, a phylogenetic analysis showed that both NRPS genes of the Ceratocystidaceae formed distinct and well supported clades in their respective phylograms, where they grouped with other known NRPSs involved in siderophore production. Overall, these findings improve our understanding of the diversity and evolution of NRPS biosynthetic pathways in the family Ceratocystidaceae.
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Lebar MD, Cary JW, Majumdar R, Carter-Wientjes CH, Mack BM, Wei Q, Uka V, De Saeger S, Diana Di Mavungu J. Identification and functional analysis of the aspergillic acid gene cluster in Aspergillus flavus. Fungal Genet Biol 2018; 116:14-23. [PMID: 29674152 DOI: 10.1016/j.fgb.2018.04.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 04/04/2018] [Accepted: 04/12/2018] [Indexed: 10/17/2022]
Abstract
Aspergillus flavus can colonize important food staples and produce aflatoxins, a group of toxic and carcinogenic secondary metabolites. Previous in silico analysis of the A. flavus genome revealed 56 gene clusters predicted to be involved in the biosynthesis of secondary metabolites. A. flavus secondary metabolites produced during infection of maize seed are of particular interest, especially with respect to their roles in the biology of the fungus. A predicted nonribosomal peptide synthetase-like (NRPS-like) gene, designated asaC (AFLA_023020), present in the uncharacterized A. flavus secondary metabolite gene cluster 11 was previously shown to be expressed during the earliest stages of maize kernel infection. Cluster 11 is composed of six additional genes encoding a number of putative decorating enzymes as well as a transporter and transcription factor. We generated knock-out mutants of the seven predicted cluster 11 genes. LC-MS analysis of extracts from knockout mutants of these genes showed that they were responsible for the synthesis of the previously characterized antimicrobial mycotoxin aspergillic acid. Extracts of the asaC mutant showed no production of aspergillic acid or its precursors. Knockout of the cluster 11 P450 oxidoreductase afforded a pyrazinone metabolite, the aspergillic acid precursor deoxyaspergillic acid. The formation of hydroxyaspergillic acid was abolished in a desaturase/hydroxylase mutant. The hydroxamic acid functional group in aspergillic acid allows the molecule to bind to iron resulting in the production of a red pigment in A. flavus identified previously as ferriaspergillin. A reduction of aflatoxin B1 and cyclopiazonic acid that correlated with reduced fungal growth was observed in maize kernel infection assays when aspergillic acid biosynthesis in A. flavus is halted.
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Affiliation(s)
- Matthew D Lebar
- Southern Regional Research Center, USDA-ARS, New Orleans, LA, USA.
| | - Jeffrey W Cary
- Southern Regional Research Center, USDA-ARS, New Orleans, LA, USA
| | | | | | - Brian M Mack
- Southern Regional Research Center, USDA-ARS, New Orleans, LA, USA
| | - Qijian Wei
- Southern Regional Research Center, USDA-ARS, New Orleans, LA, USA
| | - Valdet Uka
- Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium
| | - Sarah De Saeger
- Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium
| | - José Diana Di Mavungu
- Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium
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