Identification of regulatory mutants of Aspergillus aculeatus affected in rhamnogalacturonan hydrolase expression

Suykerbuyk, M.E.G.; Vondervoort, Peter J. I. van de; Schaap, Peter J.; Visser, Jaap

doi:10.1007/s002940050154

Cited by 6 publications

(5 citation statements)

References 12 publications

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“…In this context, expression studies in A. niger have shown that the rhamnogalacturonan acetylesterase encoding gene rgaeA was not only expressed in the presence of D-galacturonic acid, polygalacturonate and sugar beet pectin, but also in the presence of L-rhamnose [36]. Positively acting systems responding to L-rhamnose have also been suggested for the Aspergillus aculeatus rhamnogalacturonan hydrolase RhgA and the A. niger exo-rhamnogalacturonan hydrolases RgxA, RgxB and RgxC [37,38]. …”

Section: Discussionmentioning

confidence: 99%

The Aspergillus nidulans Zn(II)2Cys6transcription factor AN5673/RhaR mediates L-rhamnose utilization and the production of α-L-rhamnosidases

Pardo

Orejas

2014

Microb Cell Fact

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BackgroundVarious 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.ResultsIn this study we have identified the rhaR gene in A. nidulans and Neurospora crassa (AN5673, NCU9033) encoding a putative Zn(II)2Cys6 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-X11-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.ConclusionsTo define key elements of the L-rhamnose regulatory circuit, we characterized a DNA-binding Zn(II)2Cys6 transcription factor (RhaR) that regulates L-rhamnose induction of α-L-rhamnosidases and the pathway for its catabolism in A. nidulans, thus extending the list of fungal regulators of genes encoding plant cell wall polysaccharide degrading enzymes. These findings can be expected to provide valuable information for modulating α-L-rhamnosidase production and L-rhamnose utilization in fungi and could eventually have implications in fungal pathogenesis and pectin biotechnology.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-014-0161-9) contains supplementary material, which is available to authorized users.

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Section: Discussionmentioning

confidence: 99%

The Aspergillus nidulans Zn(II)2Cys6transcription factor AN5673/RhaR mediates L-rhamnose utilization and the production of α-L-rhamnosidases

Pardo

Orejas

2014

Microb Cell Fact

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“…In this context, expression studies in A. niger have shown that the rhamnogalacturonan acetylesterase encoding gene rgaeA was not only expressed in the presence of D-galacturonic acid, polygalacturonate and sugar beet pectin, but also in the presence of Lrhamnose [36]. Positively acting systems responding to L-rhamnose have also been suggested for the Aspergillus aculeatus rhamnogalacturonan hydrolase RhgA and the A. niger exo-rhamnogalacturonan hydrolases RgxA, RgxB and RgxC [37,38].…”

Section: Discussionmentioning

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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“…The production of pectin main-chain-cleaving enzymes (polygalacturonases, pectin lyases, rhamnogalacturonan hydrolases, and lyases) has been detected on sugar beet pectin (53), apple pectin (140,352), polygalacturonic acid (320), a combination of rhamnose and galacturonic acid (354), and soybean flour (204). However, some pectinolytic enzymes have also been reported to be produced constitutively (259,281).…”

Section: Expression Of Pectinolytic Genesmentioning

confidence: 99%

AspergillusEnzymes Involved in Degradation of Plant Cell Wall Polysaccharides

Vries

Visser

2001

Microbiol Mol Biol Rev

879

585

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SUMMARY Degradation of plant cell wall polysaccharides is of major importance in the food and feed, beverage, textile, and paper and pulp industries, as well as in several other industrial production processes. Enzymatic degradation of these polymers has received attention for many years and is becoming a more and more attractive alternative to chemical and mechanical processes. Over the past 15 years, much progress has been made in elucidating the structural characteristics of these polysaccharides and in characterizing the enzymes involved in their degradation and the genes of biotechnologically relevant microorganisms encoding these enzymes. The members of the fungal genus Aspergillus are commonly used for the production of polysaccharide-degrading enzymes. This genus produces a wide spectrum of cell wall-degrading enzymes, allowing not only complete degradation of the polysaccharides but also tailored modifications by using specific enzymes purified from these fungi. This review summarizes our current knowledge of the cell wall polysaccharide-degrading enzymes from aspergilli and the genes by which they are encoded.

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Identification of regulatory mutants of Aspergillus aculeatus affected in rhamnogalacturonan hydrolase expression

Cited by 6 publications

References 12 publications

The Aspergillus nidulans Zn(II)2Cys6transcription factor AN5673/RhaR mediates L-rhamnose utilization and the production of α-L-rhamnosidases

The Aspergillus nidulans Zn(II)2Cys6transcription factor AN5673/RhaR mediates L-rhamnose utilization and the production of α-L-rhamnosidases

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

AspergillusEnzymes Involved in Degradation of Plant Cell Wall Polysaccharides

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