Open Access Research article

Genome-wide transcriptional response of Trichoderma reesei to lignocellulose using RNA sequencing and comparison with Aspergillus niger

Laure Ries1, Steven T Pullan1, Stéphane Delmas12, Sunir Malla3, Martin J Blythe3 and David B Archer1*

Author Affiliations

1 School of Biology, University of Nottingham, Nottingham NG7 2RD, UK

2 Université Pierre et Marie Curie (UPMC, Université Paris 06), Sorbonne Universités, UMR 7138, Systématique Adapation et Évolution, 75005 Paris, France

3 Deep Seq, Centre for Genetics and Genomics, Queen’s Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK

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BMC Genomics 2013, 14:541  doi:10.1186/1471-2164-14-541

Published: 9 August 2013

Abstract

Background

A major part of second generation biofuel production is the enzymatic saccharification of lignocellulosic biomass into fermentable sugars. Many fungi produce enzymes that can saccarify lignocellulose and cocktails from several fungi, including well-studied species such as Trichoderma reesei and Aspergillus niger, are available commercially for this process. Such commercially-available enzyme cocktails are not necessarily representative of the array of enzymes used by the fungi themselves when faced with a complex lignocellulosic material. The global induction of genes in response to exposure of T. reesei to wheat straw was explored using RNA-seq and compared to published RNA-seq data and model of how A. niger senses and responds to wheat straw.

Results

In T. reesei, levels of transcript that encode known and predicted cell-wall degrading enzymes were very high after 24 h exposure to straw (approximately 13% of the total mRNA) but were less than recorded in A. niger (approximately 19% of the total mRNA). Closer analysis revealed that enzymes from the same glycoside hydrolase families but different carbohydrate esterase and polysaccharide lyase families were up-regulated in both organisms. Accessory proteins which have been hypothesised to possibly have a role in enhancing carbohydrate deconstruction in A. niger were also uncovered in T. reesei and categories of enzymes induced were in general similar to those in A. niger. Similarly to A. niger, antisense transcripts are present in T. reesei and their expression is regulated by the growth condition.

Conclusions

T. reesei uses a similar array of enzymes, for the deconstruction of a solid lignocellulosic substrate, to A. niger. This suggests a conserved strategy towards lignocellulose degradation in both saprobic fungi. This study provides a basis for further analysis and characterisation of genes shown to be highly induced in the presence of a lignocellulosic substrate. The data will help to elucidate the mechanism of solid substrate recognition and subsequent degradation by T. reesei and provide information which could prove useful for efficient production of second generation biofuels.

Keywords:
Trichoderma reesei; Aspergillus niger; Glycoside hydrolases; Carbohydrate esterases; Antisense RNA; RNA-sequencing