ATNT: an enhanced system for expression of polycistronic secondary metabolite gene clusters in Aspergillus niger

Abstract Background Fungi are treasure chests for yet unexplored natural products. However, exploitation of their real potential remains difficult as a significant proportion of biosynthetic gene clusters appears silent under standard laboratory conditions. Therefore, elucidation of novel products r...

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Main Authors: Elena Geib, Matthias Brock
Format: Article
Language:English
Published: BMC 2017-12-01
Series:Fungal Biology and Biotechnology
Subjects:
P2A
Online Access:http://link.springer.com/article/10.1186/s40694-017-0042-1
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spelling doaj-93ffe60ec5a841dbb655fa14e9afe5ac2020-11-25T01:02:25ZengBMCFungal Biology and Biotechnology2054-30852017-12-014111210.1186/s40694-017-0042-1ATNT: an enhanced system for expression of polycistronic secondary metabolite gene clusters in Aspergillus nigerElena Geib0Matthias Brock1Fungal Genetics and Biology, School of Life Sciences, University of NottinghamFungal Genetics and Biology, School of Life Sciences, University of NottinghamAbstract Background Fungi are treasure chests for yet unexplored natural products. However, exploitation of their real potential remains difficult as a significant proportion of biosynthetic gene clusters appears silent under standard laboratory conditions. Therefore, elucidation of novel products requires gene activation or heterologous expression. For heterologous gene expression, we previously developed an expression platform in Aspergillus niger that is based on the transcriptional regulator TerR and its target promoter PterA. Results In this study, we extended this system by regulating expression of terR by the doxycycline inducible Tet-on system. Reporter genes cloned under the control of the target promoter PterA remained silent in the absence of doxycycline, but were strongly expressed when doxycycline was added. Reporter quantification revealed that the coupled system results in about five times higher expression rates compared to gene expression under direct control of the Tet-on system. As production of secondary metabolites generally requires the expression of several biosynthetic genes, the suitability of the self-cleaving viral peptide sequence P2A was tested in this optimised expression system. P2A allowed polycistronic expression of genes required for Asp-melanin formation in combination with the gene coding for the red fluorescent protein tdTomato. Gene expression and Asp-melanin formation was prevented in the absence of doxycycline and strongly induced by addition of doxycycline. Fluorescence studies confirmed the correct subcellular localisation of the respective enzymes. Conclusion This tightly regulated but strongly inducible expression system enables high level production of secondary metabolites most likely even those with toxic potential. Furthermore, this system is compatible with polycistronic gene expression and, thus, suitable for the discovery of novel natural products.http://link.springer.com/article/10.1186/s40694-017-0042-1Asp-melaninP2APolycistronic mRNATet-on systemDoxycyclineTerrein biosynthetic gene cluster
collection DOAJ
language English
format Article
sources DOAJ
author Elena Geib
Matthias Brock
spellingShingle Elena Geib
Matthias Brock
ATNT: an enhanced system for expression of polycistronic secondary metabolite gene clusters in Aspergillus niger
Fungal Biology and Biotechnology
Asp-melanin
P2A
Polycistronic mRNA
Tet-on system
Doxycycline
Terrein biosynthetic gene cluster
author_facet Elena Geib
Matthias Brock
author_sort Elena Geib
title ATNT: an enhanced system for expression of polycistronic secondary metabolite gene clusters in Aspergillus niger
title_short ATNT: an enhanced system for expression of polycistronic secondary metabolite gene clusters in Aspergillus niger
title_full ATNT: an enhanced system for expression of polycistronic secondary metabolite gene clusters in Aspergillus niger
title_fullStr ATNT: an enhanced system for expression of polycistronic secondary metabolite gene clusters in Aspergillus niger
title_full_unstemmed ATNT: an enhanced system for expression of polycistronic secondary metabolite gene clusters in Aspergillus niger
title_sort atnt: an enhanced system for expression of polycistronic secondary metabolite gene clusters in aspergillus niger
publisher BMC
series Fungal Biology and Biotechnology
issn 2054-3085
publishDate 2017-12-01
description Abstract Background Fungi are treasure chests for yet unexplored natural products. However, exploitation of their real potential remains difficult as a significant proportion of biosynthetic gene clusters appears silent under standard laboratory conditions. Therefore, elucidation of novel products requires gene activation or heterologous expression. For heterologous gene expression, we previously developed an expression platform in Aspergillus niger that is based on the transcriptional regulator TerR and its target promoter PterA. Results In this study, we extended this system by regulating expression of terR by the doxycycline inducible Tet-on system. Reporter genes cloned under the control of the target promoter PterA remained silent in the absence of doxycycline, but were strongly expressed when doxycycline was added. Reporter quantification revealed that the coupled system results in about five times higher expression rates compared to gene expression under direct control of the Tet-on system. As production of secondary metabolites generally requires the expression of several biosynthetic genes, the suitability of the self-cleaving viral peptide sequence P2A was tested in this optimised expression system. P2A allowed polycistronic expression of genes required for Asp-melanin formation in combination with the gene coding for the red fluorescent protein tdTomato. Gene expression and Asp-melanin formation was prevented in the absence of doxycycline and strongly induced by addition of doxycycline. Fluorescence studies confirmed the correct subcellular localisation of the respective enzymes. Conclusion This tightly regulated but strongly inducible expression system enables high level production of secondary metabolites most likely even those with toxic potential. Furthermore, this system is compatible with polycistronic gene expression and, thus, suitable for the discovery of novel natural products.
topic Asp-melanin
P2A
Polycistronic mRNA
Tet-on system
Doxycycline
Terrein biosynthetic gene cluster
url http://link.springer.com/article/10.1186/s40694-017-0042-1
work_keys_str_mv AT elenageib atntanenhancedsystemforexpressionofpolycistronicsecondarymetabolitegeneclustersinaspergillusniger
AT matthiasbrock atntanenhancedsystemforexpressionofpolycistronicsecondarymetabolitegeneclustersinaspergillusniger
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