ORF Ι of Mycovirus SsNSRV-1 is Associated with Debilitating Symptoms of Sclerotinia sclerotiorum.

Zhixiao Gao,Jiasen Cheng,Junyan Wu,Daohong Jiang,Jiatao Xie,Yang Lin

doi:10.3390/v12040456

Abstract

We previously identified Sclerotinia sclerotiorum negative-stranded virus 1 (SsNSRV-1), the first (−) ssRNA mycovirus, associated with hypovirulence of its fungal host Sclerotinia sclerotiorum. In this study, functional analysis of Open Reading Frame Ι (ORF Ι) of SsNSRV-1 was performed. The integration and expression of ORF Ι led to defects in hyphal tips, vegetative growth, and virulence of the mutant strains of S. sclerotiorum. Further, differentially expressed genes (DEGs) responding to the expression of ORF Ι were identified by transcriptome analysis. In all, 686 DEGs consisted of 267 up-regulated genes and 419 down-regulated genes. DEGs reprogramed by ORF Ι were relevant to secretory proteins, pathogenicity, transcription, transmembrane transport, protein biosynthesis, modification, and metabolism. Alternative splicing was also detected in all mutant strains, but not in hypovirulent strain AH98, which was co-infected by SsNSRV-1 and Sclerotinia sclerotiorum hypovirus 1 (SsHV-1). Thus, the integrity of SsNSRV-1 genome may be necessary to protect viral mRNA from splicing and inactivation by the host. Taken together, the results suggested that protein ORF Ι could regulate the transcription, translation, and modification of host genes in order to facilitate viral proliferation and reduce the virulence of the host. Therefore, ORF Ι may be a potential gene used for the prevention of S. sclerotiorum.

Highlights

Mycoviruses, the viruses that infect fungi, are ubiquitous in all kinds of fungi [1]. many mycoviruses are commonly associated with cryptic or latent infections of the fungal host, a few of them are reported to confer hypovirulence or hypervirulence to their host
The results indicated that the secondary structure of Open Reading Frame I (ORF I) was mainly composed of helical structures, which had two strands and a coiled helix, but no transmembrane helix
The results demonstrated that the expression of gene ORF I could cause defects in vegetative growth and the pathogenicity of its fungal host

Summary

Introduction

Many mycoviruses are commonly associated with cryptic or latent infections of the fungal host, a few of them are reported to confer hypovirulence or hypervirulence to their host. Of these mycoviruses, hypoviruses are considered as potential biological agents to prevent fungal diseases [2]. Rosellinia necatrix megabirnavirus 1 and Sclerotinia sclerotiorum hypovirulence-associated DNA virus 1 are demonstrated to have the potential to prevent fungal diseases caused by their hosts [5,6,7]. The first negative-stranded RNA virus isolated from Sclerotinia sclerotiorum hypovirulent strain

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Results

Conclusion