Enhanced glycosyl hydrolase production in Aspergillus nidulans using transcription factor engineering approaches

Tamayo-Ramos, Juan Antonio; Orejas, Margarita

doi:10.1186/1754-6834-7-103

Cited by 22 publications

(16 citation statements)

References 48 publications

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“…[1-5 and references therein]. In this regard, engineered fungal cells with enhanced rhamnosidase yields have been reported [6,7]. In addition, these enzymes also are involved in the detoxification of plant secondary metabolites and hence they could play a role in evading plant defences against fungal attacks [8,9 and references therein].…”

Section: Introductionmentioning

confidence: 99%

The Aspergillus nidulans Zn(II) 2 Cys 6 transcription factor AN5673/RhaR mediates L-rhamnose utilization and the production of ¿-L-rhamnosidases

Pardo

Orejas

2014

Microb Cell Fact

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Background: Various plant-derived substrates contain L-rhamnose that can be assimilated by many fungi and its liberation is catalyzed by α-L-rhamnosidases. Initial data obtained in our laboratory focussing on two Aspergillus nidulans α-L-rhamnosidase genes (rhaA and rhaE) showed α-L-rhamnosidase production to be tightly controlled at the level of transcription by the carbon source available. Whilst induction is effected by L-rhamnose, unlike many other glycosyl hydrolase genes repression by glucose and other carbon sources occurs in a manner independent of CreA. To date regulatory genes affecting L-rhamnose utilization and the production of enzymes that yield L-rhamnose as a product have not been identified in A. nidulans. The purpose of the present study is to characterize the corresponding α-L-rhamnosidase transactivator. Results: In this study we have identified the rhaR gene in A. nidulans and Neurospora crassa (AN5673, NCU9033) encoding a putative Zn(II) 2 Cys 6 DNA-binding protein. Genetic evidence indicates that its product acts in a positive manner to induce transcription of the A. nidulans L-rhamnose regulon. rhaR-deleted mutants showed reduced ability to induce expression of the α-L-rhamnosidase genes rhaA and rhaE and concomitant reduction in α-L-rhamnosidase production. The rhaR deletion phenotype also results in a significant reduction in growth on L-rhamnose that correlates with reduced expression of the L-rhamnonate dehydratase catabolic gene lraC (AN5672). Gel mobility shift assays revealed RhaR to be a DNA binding protein recognizing a partially symmetrical CGG-X 11 -CCG sequence within the rhaA promoter. Expression of rhaR alone is insufficient for induction since its mRNA accumulates even in the absence of L-rhamnose, therefore the presence of both functional RhaR and L-rhamnose are absolutely required. In N. crassa, deletion of rhaR also impairs growth on L-rhamnose.

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Section: Introductionmentioning

confidence: 99%

The Aspergillus nidulans Zn(II) 2 Cys 6 transcription factor AN5673/RhaR mediates L-rhamnose utilization and the production of ¿-L-rhamnosidases

Pardo

Orejas

2014

Microb Cell Fact

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“…In the deregulated XlnR background, the activation of PacC was impeded by preventing the cleavage of the inactive form of PacC. This resulted in increased activity of a heterologously expressed protein whose expression was driven by the promoter of an acidic-expressed CAZyme-encoding gene [174]. This study in A. nidulans highlights the potential benefit of employing a transcription factor engineering approach in an industrially relevant strain, and applies knowledge on the transcriptional regulation of fungi exposed to lignocellulose.…”

Section: Applications With Prior Understanding Of the Regulatory Mechmentioning

confidence: 98%

“…Constitutively over-expressing XlnR led to earlier and increased protein production [174]. Under alkaline conditions, PacC (as described in Section III), activates alkaline-expressed genes and supresses acidic-expressed genes [103].…”

Section: Applications With Prior Understanding Of the Regulatory Mechmentioning

confidence: 99%

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Transcriptional Regulation and Responses in Filamentous Fungi Exposed to Lignocellulose

2015

Mycology: Current and Future Developments

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Biofuels derived from lignocellulose are attractive alternative fuels but their production suffers from a costly and inefficient saccharification step that uses fungal enzymes. One route to improve this efficiency is to understand better the transcriptional regulation and responses of filamentous fungi to lignocellulose. Sensing and initial contact of the fungus with lignocellulose is an important aspect. Differences and similarities in the responses of fungi to different lignocellulosic substrates can partly be explained with existing understanding of several key regulators and their mode of action, as will be demonstrated for Trichoderma reesei, Neurospora crassa and Aspergillus spp. The regulation of genes encoding Carbohydrate Active enZymes (CAZymes) is influenced by the presence of carbohydrate monomers and short oligosaccharides, as well as the external stimuli of pH and light. We explore several important aspects of the response to lignocellulose that are not related to genes encoding CAZymes, namely the regulation of transporters, accessory proteins and stress responses. The regulation of gene expression is examined from the perspective of mixed cultures and models are presented for the nature of the transcriptional basis for any beneficial effects of such mixed cultures. Various applications in biofuel technology are based on manipulating transcriptional regulation and learning from fungal responses to lignocelluloses. Here we critically access the application of fungal transcriptional responses to industrial saccharification reactions. As part of this chapter, selected regulatory mechanisms are also explored in more detail.

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“…It is an efficient degrader of the major plant cell wall polysaccharides cellulose, hemicellulose and pectin (de Souza et al, 2013), and is one of the main industrial producers of commercial enzymes for plant biomass conversion due to its high enzyme secretory capacity (Tamayo- Ramos and Orejas, 2014). In the last decades, its versatile arsenal of extracellular enzymes for lignocellulose depolymerisation (de Vries and Visser, 2001), and the molecular mechanisms controlling their expression, have been well described (Battaglia et al, 2011;Gruben et al, 2014;.…”

Section: Introductionmentioning

confidence: 99%

Organic acid production in Aspergillus niger and other filamentous fungi

Odoni

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Propositions1. Medium acidification is primarily a cause, rather than an effect, of Aspergillus niger citrate secretion.(this thesis) 2. A holistic systems biology approach should consider the organism in the context of its environment.(this thesis) 3. Metabolism has more than two spacial dimensions and should be studied as a system rather than a map.4. Cancer cells behave as a microorganism in a foreign environment.5. Referrals to authors rather than researchers highlights the skewed perception of scientific worth.6. Reviews can both progress and regress a field.7. Recent history suggests that "common sense" is an oxymoron.8. True understanding, and thus friendship, arises from a common mindset rather than a common nationality.Propositions belonging to the thesis, entitled

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Enhanced glycosyl hydrolase production in Aspergillus nidulans using transcription factor engineering approaches

Cited by 22 publications

References 48 publications

The Aspergillus nidulans Zn(II) 2 Cys 6 transcription factor AN5673/RhaR mediates L-rhamnose utilization and the production of ¿-L-rhamnosidases

The Aspergillus nidulans Zn(II) 2 Cys 6 transcription factor AN5673/RhaR mediates L-rhamnose utilization and the production of ¿-L-rhamnosidases

Transcriptional Regulation and Responses in Filamentous Fungi Exposed to Lignocellulose

Organic acid production in Aspergillus niger and other filamentous fungi

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