Identification of microRNA-like RNAs in the filamentous fungus Trichoderma reesei by Solexa sequencing
MicroRNAs (miRNAs) are small non-coding RNAs capable of negatively regulating gene expression. Trichoderma reesei is an industrial filamentous fungus that can secrete abundant hydrolases for cellulosic biofuels. Recently, microRNA-like RNAs (milRNAs) were discovered in several filamentous fungi rather than T. reesei. The purpose of this study was to explore the presence of milRNA in T. reesei, to characterize the differential expression of T. reesei milRNA under cellulose induction, and to reveal the target genes of milRNA involved in cellulase production. Two small RNA libraries of cellulose induction (IN) or non-induction (CON) were generated and sequenced using Solexa sequencing technology. A total of 664,463 and 529,545 unique sequences, representing 1,271 and 1,021 unique small RNAs, were obtained from the IN and CON samples, respectively. Thirteen milRNAs were finally identified in T. reesei using the hairpin structure analysis. The milRNAs profiles obtained in deep sequencing were validated by RT-qPCR assay. The miRanda program predicts a number of potential targets for T. reesei milRNAs, including several hydrolases and carbon catabolite repressor Cre1.The presence and differential expression of T. reesei milRNAs, along with their predicted targets indicate that milRNAs might play a regulatory role in cellulase induction. This work lays foundation for further functional study of fungal milRNAs and their industrial application. Overall design: Evaluation of the small RNA expression in Trichoderma reesei under cellulase induction (IN) or non-induction (CON) conditions