A long noncoding RNA promotes cellulase expression in Trichoderma reesei

Astrid R Mach-Aigner,Marion E Pucher,Robert L Mach,Petra Till

doi:10.1186/s13068-018-1081-4

Astrid R Mach-Aigner, Marion E Pucher + Show 2 more

Open Access

https://doi.org/10.1186/s13068-018-1081-4

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Abstract

BackgroundDue to its capability to secrete large quantities of plant biomass degrading enzymes (PBDE), Trichoderma reesei is widely applied for industrial purposes. In nature, expression of PBDE is efficiently regulated in this fungus. Several factors involved in this regulatory network have been identified. However, most of them are transcription factors. Long noncoding RNAs (lncRNAs) emerged as common players acting on epigenetic or transcriptional regulation in several eukaryotic organisms. To date, no lncRNA has been described in filamentous fungi.ResultsA lncRNA termed HAX1 was identified in T. reesei QM9414. In this study, it was characterized and evidence for its regulatory impact on cellulase expression was provided. Interestingly, different versions of HAX1 were identified in different strains (namely, QM6a, QM9414, and Rut-C30), varying in terms of RNA length. Remarkably, considerable longer variants of this lncRNA are present in hypercellulolytic strains compared to the wild-type strain QM6a. Based on these results, a correlation between RNA length and the functional impact of HAX1 on PBDE expression was supposed. This assumption was verified by overexpressing the most abundant HAX1 versions identified in QM6a, QM9414, and Rut-C30. Such HAX1 overexpression on the one hand was suitable for regaining the function in hax1 disruption strains, and on the other hand resulted in notably higher cellulase activities in QM6a, especially by the expression of longer HAX1 versions.ConclusionWith HAX1, for the first time the regulatory role of a lncRNA in filamentous fungi was uncovered. Besides this, a new player involved in the complex regulation of PBDE expression in T. reesei was identified. Due to its enhancing effect on cellulase activity, HAX1 was shown to be not only interesting for basic research, but also a promising candidate for expanding the set of biotechnological tools for industrial application of T. reesei.

Highlights

Due to its capability to secrete large quantities of plant biomass degrading enzymes (PBDE), Trichoderma reesei is widely applied for industrial purposes
An undescribed gene locus influences cellulase expression in T. reesei QM9414 Commonly, phenotypic investigation of strains generated by targeted mutagenesis requires a reference strain carrying solely the marker gene
The cellulase activity was reduced about 50% in cultures that were induced on lactose (Fig. 1B)

Summary

Introduction

Due to its capability to secrete large quantities of plant biomass degrading enzymes (PBDE), Trichoderma reesei is widely applied for industrial purposes. Several factors involved in this regulatory network have been identified. Most of them are transcrip‐ tion factors. The filamentous fungus Trichoderma reesei (teleomorph Hypocrea jecorina [1], phylum Ascomycota) is one of the most potent producers of plant biomass degrading enzymes (PBDE) used in industrial applications. Two. Till et al Biotechnol Biofuels (2018) 11:78 strains derived from QM6a via random mutagenesis and selection for increased PBDE expression are QM9414 and Rut-C30 [19]. Rut-C30 is characterized by strongly increased cellulase activities and partial carbon catabolite derepression and became the progenitor of most industrial strains [19,20,21]

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