Chilling Stress Triggers VvAgo1-Mediated miRNA-Like RNA Biogenesis in Volvariella volvacea.

Ming Gong,Dapeng Bao,Yan Zhao,Qi Tan,Yan Li,Jinsong Zhang,Ying Wang,Yingying Wu,Junjun Shang,Ruiheng Yang,Jianing Wan

doi:10.3389/fmicb.2020.523593

Abstract

In Volvariella volvacea, an important species of edible mushroom, cryogenic autolysis is a typical phenomenon that occurs during abnormal metabolism. Analysis of gene expression profiling and qPCR showed that chilling stress (CS) significantly and continuously upregulated only one type of Argonaute in V. volvacea, i.e., VvAgo1. Structural and evolutionary analysis revealed that VvAgo1 belongs to the Ago-like family, and its evolution has involved gene duplication, subsequent gene loss, and purifying selection. Analysis of its interaction network and expression suggested that CS triggers VvAgo1-mediated miRNA-like RNA (milRNA) biogenesis in V. volvacea V23 but not in VH3 (a composite mutant strain from V23 with improved CS resistance). Small RNA sequencing and qPCR analysis confirmed that CS triggered the increased milRNA expression in V23 and not in VH3. The predicted target genes of the increased milRNAs were enriched in several pathways, such as signal transduction and ubiquitination. Heatmap analysis showed that CS altered the expression profile of milRNAs with their target genes related to signal transduction and ubiquitination in V23. Combined analysis of transcriptome and proteome data confirmed that most of the target genes of the increased milRNAs were not translated into proteins. Our observations indicate that CS might trigger VvAgo1-mediated RNAi to facilitate the cryogenic autolysis of V. volvacea.

Highlights

Volvariella volvacea, known as the straw mushroom or Chinese mushroom, is among the most extensively cultivated mushrooms in tropical and sub-tropical regions, but it requires relatively high temperatures (28–35◦C) for vegetative growth and fruiting (Chen et al, 2003; Bao et al, 2013; Gong et al, 2016)
As RNA silencing is a sequence-specific gene regulation system conserved in eukaryotes (Sasaki and Tomari, 2012), the chilling stressresponsive feature of VvAgo1 (Bao et al, 2013) indicates that it may be involved in the cryogenic autolysis of V. volvacea via miRNA-like RNA (milRNA)
VvAgo1 did not rise at 2 h, the trend toward its upregulation was apparent after cold treatment. quantitative real-time PCR (qPCR) confirmed that chilling stress (CS) did not trigger the significantly upregulated expression of the other four Agos in V23 (Supplementary Figure S1)

Summary

Introduction

Volvariella volvacea, known as the straw mushroom or Chinese mushroom, is among the most extensively cultivated mushrooms in tropical and sub-tropical regions, but it requires relatively high temperatures (28–35◦C) for vegetative growth and fruiting (Chen et al, 2003; Bao et al, 2013; Gong et al, 2016). Cryogenic Autolysis of Volvariella volvacea shelf-life of this mushroom hampers its distribution over long distances and limits its cultivation and popularization. Cryogenic autolysis of V. volvacea indirectly affects the use of straw as an energy resource and has significant economic consequences, given that the annual output of V. volvacea on the Chinese mainland accounted for more than 80% of the global production of this commodity in 2010 (Bao et al, 2013). The issue of cryogenic autolysis is both an interesting scientific problem and a practical economic matter (Gong et al, 2016)

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Results

Conclusion