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Fungal Genet Biol. 2014 Nov;72:34-47. doi: 10.1016/j.fgb.2014.04.006. Epub 2014 Apr 29.

The role of carbon starvation in the induction of enzymes that degrade plant-derived carbohydrates in Aspergillus niger.

Author information

1
School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK. Electronic address: jolanda.van_munster@nottingham.ac.uk.
2
School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK. Electronic address: paul.daly@nottingham.ac.uk.
3
School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK. Electronic address: stephane.delmas@upmc.fr.
4
School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK. Electronic address: steven.pullan@phe.gov.uk.
5
Deep Seq, Faculty of Medicine and Health Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK. Electronic address: martin.blythe@nottingham.ac.uk.
6
Deep Seq, Faculty of Medicine and Health Sciences, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK. Electronic address: sunir.malla@nottingham.ac.uk.
7
School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK. Electronic address: matt.kokolski@nottingham.ac.uk.
8
School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK. Electronic address: emelie_noltorp@hotmail.com.
9
School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK. Electronic address: kristin.wennberg@telia.com.
10
School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK. Electronic address: richard.fetherston@hotmail.co.uk.
11
Biological Mass Spectrometry Facility biOMICS, University of Sheffield, Brook Hill Road, Sheffield S3 7HF, UK. Electronic address: r.g.beniston@sheffield.ac.uk.
12
Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK. Electronic address: xly20@cam.ac.uk.
13
Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK. Electronic address: pd101@cam.ac.uk.
14
School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK. Electronic address: david.archer@nottingham.ac.uk.

Abstract

Fungi are an important source of enzymes for saccharification of plant polysaccharides and production of biofuels. Understanding of the regulation and induction of expression of genes encoding these enzymes is still incomplete. To explore the induction mechanism, we analysed the response of the industrially important fungus Aspergillus niger to wheat straw, with a focus on events occurring shortly after exposure to the substrate. RNA sequencing showed that the transcriptional response after 6h of exposure to wheat straw was very different from the response at 24h of exposure to the same substrate. For example, less than half of the genes encoding carbohydrate active enzymes that were induced after 24h of exposure to wheat straw, were also induced after 6h exposure. Importantly, over a third of the genes induced after 6h of exposure to wheat straw were also induced during 6h of carbon starvation, indicating that carbon starvation is probably an important factor in the early response to wheat straw. The up-regulation of the expression of a high number of genes encoding CAZymes that are active on plant-derived carbohydrates during early carbon starvation suggests that these enzymes could be involved in a scouting role during starvation, releasing inducing sugars from complex plant polysaccharides. We show, using proteomics, that carbon-starved cultures indeed release CAZymes with predicted activity on plant polysaccharides. Analysis of the enzymatic activity and the reaction products, indicates that these proteins are enzymes that can degrade various plant polysaccharides to generate both known, as well as potentially new, inducers of CAZymes.

KEYWORDS:

Aspergillus niger; CAZy enzymes; Carbon starvation; Inducer; Lignocellulose; Transcriptome

PMID:
24792495
PMCID:
PMC4217149
DOI:
10.1016/j.fgb.2014.04.006
[Indexed for MEDLINE]
Free PMC Article

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