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L-Rhamnose induction of Aspergillus nidulans α-L-rhamnosidase genes is glucose repressed via a CreA-independent mechanism acting at the level of inducer uptake

BACKGROUND: Little is known about the structure and regulation of fungal α-L-rhamnosidase genes despite increasing interest in the biotechnological potential of the enzymes that they encode. Whilst the paradigmatic filamentous fungus Aspergillus nidulans growing on L-rhamnose produces an α-L-rhamnos...

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Autores principales: Tamayo-Ramos, Juan A, Flipphi, Michel, Pardo, Ester, Manzanares, Paloma, Orejas, Margarita
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2012
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3312857/
https://www.ncbi.nlm.nih.gov/pubmed/22353731
http://dx.doi.org/10.1186/1475-2859-11-26
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author Tamayo-Ramos, Juan A
Flipphi, Michel
Pardo, Ester
Manzanares, Paloma
Orejas, Margarita
author_facet Tamayo-Ramos, Juan A
Flipphi, Michel
Pardo, Ester
Manzanares, Paloma
Orejas, Margarita
author_sort Tamayo-Ramos, Juan A
collection PubMed
description BACKGROUND: Little is known about the structure and regulation of fungal α-L-rhamnosidase genes despite increasing interest in the biotechnological potential of the enzymes that they encode. Whilst the paradigmatic filamentous fungus Aspergillus nidulans growing on L-rhamnose produces an α-L-rhamnosidase suitable for oenological applications, at least eight genes encoding putative α-L-rhamnosidases have been found in its genome. In the current work we have identified the gene (rhaE) encoding the former activity, and characterization of its expression has revealed a novel regulatory mechanism. A shared pattern of expression has also been observed for a second α-L-rhamnosidase gene, (AN10277/rhaA). RESULTS: Amino acid sequence data for the oenological α-L-rhamnosidase were determined using MALDI-TOF mass spectrometry and correspond to the amino acid sequence deduced from AN7151 (rhaE). The cDNA of rhaE was expressed in Saccharomyces cerevisiae and yielded pNP-rhamnohydrolase activity. Phylogenetic analysis has revealed this eukaryotic α-L-rhamnosidase to be the first such enzyme found to be more closely related to bacterial rhamnosidases than other α-L-rhamnosidases of fungal origin. Northern analyses of diverse A. nidulans strains cultivated under different growth conditions indicate that rhaA and rhaE are induced by L-rhamnose and repressed by D-glucose as well as other carbon sources, some of which are considered to be non-repressive growth substrates. Interestingly, the transcriptional repression is independent of the wide domain carbon catabolite repressor CreA. Gene induction and glucose repression of these rha genes correlate with the uptake, or lack of it, of the inducing carbon source L-rhamnose, suggesting a prominent role for inducer exclusion in repression. CONCLUSIONS: The A. nidulans rhaE gene encodes an α-L-rhamnosidase phylogenetically distant to those described in filamentous fungi, and its expression is regulated by a novel CreA-independent mechanism. The identification of rhaE and the characterization of its regulation will facilitate the design of strategies to overproduce the encoded enzyme - or homologs from other fungi - for industrial applications. Moreover, A. nidulans α-L-rhamnosidase encoding genes could serve as prototypes for fungal genes coding for plant cell wall degrading enzymes regulated by a novel mechanism of CCR.
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spelling pubmed-33128572012-03-27 L-Rhamnose induction of Aspergillus nidulans α-L-rhamnosidase genes is glucose repressed via a CreA-independent mechanism acting at the level of inducer uptake Tamayo-Ramos, Juan A Flipphi, Michel Pardo, Ester Manzanares, Paloma Orejas, Margarita Microb Cell Fact Research BACKGROUND: Little is known about the structure and regulation of fungal α-L-rhamnosidase genes despite increasing interest in the biotechnological potential of the enzymes that they encode. Whilst the paradigmatic filamentous fungus Aspergillus nidulans growing on L-rhamnose produces an α-L-rhamnosidase suitable for oenological applications, at least eight genes encoding putative α-L-rhamnosidases have been found in its genome. In the current work we have identified the gene (rhaE) encoding the former activity, and characterization of its expression has revealed a novel regulatory mechanism. A shared pattern of expression has also been observed for a second α-L-rhamnosidase gene, (AN10277/rhaA). RESULTS: Amino acid sequence data for the oenological α-L-rhamnosidase were determined using MALDI-TOF mass spectrometry and correspond to the amino acid sequence deduced from AN7151 (rhaE). The cDNA of rhaE was expressed in Saccharomyces cerevisiae and yielded pNP-rhamnohydrolase activity. Phylogenetic analysis has revealed this eukaryotic α-L-rhamnosidase to be the first such enzyme found to be more closely related to bacterial rhamnosidases than other α-L-rhamnosidases of fungal origin. Northern analyses of diverse A. nidulans strains cultivated under different growth conditions indicate that rhaA and rhaE are induced by L-rhamnose and repressed by D-glucose as well as other carbon sources, some of which are considered to be non-repressive growth substrates. Interestingly, the transcriptional repression is independent of the wide domain carbon catabolite repressor CreA. Gene induction and glucose repression of these rha genes correlate with the uptake, or lack of it, of the inducing carbon source L-rhamnose, suggesting a prominent role for inducer exclusion in repression. CONCLUSIONS: The A. nidulans rhaE gene encodes an α-L-rhamnosidase phylogenetically distant to those described in filamentous fungi, and its expression is regulated by a novel CreA-independent mechanism. The identification of rhaE and the characterization of its regulation will facilitate the design of strategies to overproduce the encoded enzyme - or homologs from other fungi - for industrial applications. Moreover, A. nidulans α-L-rhamnosidase encoding genes could serve as prototypes for fungal genes coding for plant cell wall degrading enzymes regulated by a novel mechanism of CCR. BioMed Central 2012-02-21 /pmc/articles/PMC3312857/ /pubmed/22353731 http://dx.doi.org/10.1186/1475-2859-11-26 Text en Copyright ©2012 Tamayo-Ramos et al; BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research
Tamayo-Ramos, Juan A
Flipphi, Michel
Pardo, Ester
Manzanares, Paloma
Orejas, Margarita
L-Rhamnose induction of Aspergillus nidulans α-L-rhamnosidase genes is glucose repressed via a CreA-independent mechanism acting at the level of inducer uptake
title L-Rhamnose induction of Aspergillus nidulans α-L-rhamnosidase genes is glucose repressed via a CreA-independent mechanism acting at the level of inducer uptake
title_full L-Rhamnose induction of Aspergillus nidulans α-L-rhamnosidase genes is glucose repressed via a CreA-independent mechanism acting at the level of inducer uptake
title_fullStr L-Rhamnose induction of Aspergillus nidulans α-L-rhamnosidase genes is glucose repressed via a CreA-independent mechanism acting at the level of inducer uptake
title_full_unstemmed L-Rhamnose induction of Aspergillus nidulans α-L-rhamnosidase genes is glucose repressed via a CreA-independent mechanism acting at the level of inducer uptake
title_short L-Rhamnose induction of Aspergillus nidulans α-L-rhamnosidase genes is glucose repressed via a CreA-independent mechanism acting at the level of inducer uptake
title_sort l-rhamnose induction of aspergillus nidulans α-l-rhamnosidase genes is glucose repressed via a crea-independent mechanism acting at the level of inducer uptake
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3312857/
https://www.ncbi.nlm.nih.gov/pubmed/22353731
http://dx.doi.org/10.1186/1475-2859-11-26
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