Tr-milRNA1 Contributes to Lignocellulase Secretion under Heat Stress by Regulating the Lectin-Type Cargo Receptor Gene Trvip36 in Trichoderma guizhouence NJAU 4742.

Tuo Li,Yang Liu,Qin Wang,Jinding Liu,Qirong Shen,Ting Li,Dongyang Liu

doi:10.3390/jof7120997

Tuo Li, Yang Liu + Show 5 more

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https://doi.org/10.3390/jof7120997

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Abstract

Background: MicroRNA plays an important role in multifarious biological processes by regulating their corresponding target genes. However, the biological function and regulatory mechanism of fungal microRNA-like RNAs (milRNAs) remain poorly understood. Methods: In this study, combined with deep sequencing and bioinformatics analysis, milRNAs and their targets from Trichoderma guizhouence NJAU 4742 were isolated and identified under solid-state fermentation (SSF) by using rice straw as the sole carbon source at 28 °C and 37 °C, respectively. Results: A critical milRNA, TGA1_S04_31828 (Tr-milRNA1), was highly expressed under heat stress (37 °C) and adaptively regulated lignocellulase secretion. Overexpression of Tr-milRNA1 (OE-Tr-milRNA1) did not affect vegetative growth, but significantly increased lignocellulose utilization under heat stress. Based on the bioinformatics analysis and qPCR validation, a target of Tr-milRNA1 was identified as Trvip36, a lectin-type cargo receptor. The expression of Tr-milRNA1 and Trvip36 showed a divergent trend under SSF when the temperature was increased from 28 °C to 37 °C. In addition, the expression of Trvip36 was suppressed significantly in Tr-milRNA1 overexpression strain (OE-Tr-milRNA1). Compared with the wild type, deletion of Trvip36 (ΔTrvip36) significantly improved the secretion of lignocellulases by reducing the retention of lignocellulases in the ER under heat stress. Conclusions: Tr-milRNA1 from NJAU 4742 improved lignocellulose utilization under heat stress by regulating the expression of the corresponding target gene Trvip36. These findings might open avenues for exploring the mechanism of lignocellulase secretion in filamentous fungi.

Highlights

Small RNA-induced RNA interference (RNAi) is a broad biological process that can lead to sequence-specific degradation or translational repression of target mRNAs [1,2]
In order to determine whether microRNA-like RNAs (milRNAs) are involved in the regulation of cellulase secretion in NJAU 4742 under heat stress, two small RNA libraries were generated from
56 putative milRNAs were identified in NJAU 4742, and 47 and 46 Tr-milRNAs were identified at T28 and T37, respectively (Table 1 and Figure 1a)

Summary

Introduction

Small RNA (sRNA)-induced RNA interference (RNAi) is a broad biological process that can lead to sequence-specific degradation or translational repression of target mRNAs [1,2]. The common feature of RNAi pathways is that sRNAs bind to Argonaute (AGO). Proteins and guide the RNA-induced silencing complex (RISC) to RNAs with complementary sequences [3,4]. RNAi is highly conserved in eukaryotes, including the majority of the fungal kingdom [5]. Fungal RNA interference was first discovered in Neurospora crassa. Introducing fragments of albino-1 (al-1) or albino-3 (al-3), which are required for carotenoid biosynthesis, reduced al-1, or al-3 mRNA levels and resulted in an albino phenotype [6]. With the expansion of fungal genome information, RNAi pathway components have been found in most fungal species.

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