A long noncoding RNA promotes cellulase expression in .

Background: Due to its capability to secrete large quantities of plant biomass degrading enzymes (PBDE), 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.

Results: A lncRNA termed was identified in QM9414. In this study, it was characterized and evidence for its regulatory impact on cellulase expression was provided. Interestingly, different versions of 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 on PBDE expression was supposed. This assumption was verified by overexpressing the most abundant versions identified in QM6a, QM9414, and Rut-C30. Such overexpression on the one hand was suitable for regaining the function in disruption strains, and on the other hand resulted in notably higher cellulase activities in QM6a, especially by the expression of longer versions.

Conclusion: With 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 was identified. Due to its enhancing effect on cellulase activity, 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 .