Characterization of a Novel Ourmia-Like Mycovirus Infecting Magnaporthe oryzae and Implications for Viral Diversity and Evolution.

Chang Li,Jie Zhong,Hong Zhu,Jun Zhu,Bi Gao,Qian Zhou

doi:10.3390/v11030223

Abstract

Here, the molecular characterization of a novel mycovirus that was isolated from a phytopathogenic fungus Magnaporthe oryzae and designed as Magnaporthe oryzae ourmia-like virus 4 (MOLV4) is reported. MOLV4 has a genome that is 2497 bp long and possesses a single open reading frame (ORF), which encodes the product RNA-dependent RNA polymerase (RdRp). Sequence similarities were found between the MOLV4 encoded RdRp and the counterparts of a few previously reported ourmia-like mycoviruses. Virus-curing and biological comparison indicate that the virus has no or mild effects on the morphology and mycelium growth rate of the host fungus. Phylogenetic analysis using the RdRp aa sequences was performed. The results show that MOLV4 is clustered with the ourmia-like mycoviruses, forming a clade closely related to ourmiaviruses but distinct from narnaviruses. In addition, database searches revealed that several MOLV4-related sequences are present in the transcriptome shotgun assembly (TSA) library, expressed sequence tag database (ESTdb), whole-genome shotgun (WGS) library, and genomic survey sequences (GSS) libraries of a few other species of eukaryote organisms. Our results show that MOLV4, together with other similar ourmia-like mycoviruses, might represent a virus clade that links the plant ourmiaviruses and fungal narnaviruses and has a wide range of hosts.

Highlights

IntroductionMycoviruses (fungal viruses) are ubiquitous and can infect and replicate in all major taxa of fungi, including plant-pathogenic fungi [1]
Mycoviruses are ubiquitous and can infect and replicate in all major taxa of fungi, including plant-pathogenic fungi [1]
We identified a novel mycovirus, Magnaporthe oryzae ourmia-like virus 4 (MOLV4), isolated from the plant pathogenic fungus M. oryzae

Summary

Introduction

Mycoviruses (fungal viruses) are ubiquitous and can infect and replicate in all major taxa of fungi, including plant-pathogenic fungi [1]. The vast majority of mycoviruses are associated with latent infections, the infections of some mycoviruses can cause clear phenotype alterations in growth, sporulation, pigmentation, and virulence, that often lead to hypovirulence and debilitation. A number of mycoviruses are reported to have beneficial effects on the host fungi, such as the increase of virulence (hypervirulence) in plant pathogenic fungi or oomycetes [2,3], the enhancement of competitive ability via producing killer proteins in some yeasts [4,5], and the improvement of heat tolerance in plants conferred by the symbiotic host fungus [6]. Many mycoviruses were subsequently found, largely expanding the knowledge of mycoviral diversity, ecology, and evolution

Methods

Results

Conclusion