Diverse Partitiviruses From the Phytopathogenic Fungus, Rosellinia necatrix

Paul Telengech,Kiwamu Hyodo,Satoko Kanematsu,Hideki Kondo,Juan Manuel Arjona-López,Sakae Hisano,Nobuhiro Suzuki,Carlos José López-Herrera,Cyrus Mugambi

doi:10.3389/fmicb.2020.01064

Abstract

Partitiviruses (dsRNA viruses, family Partitiviridae) are ubiquitously detected in plants and fungi. Although previous surveys suggested their omnipresence in the white root rot fungus, Rosellinia necatrix, only a few of them have been molecularly and biologically characterized thus far. We report the characterization of a total of 20 partitiviruses from 16 R. necatrix strains belonging to 15 new species, for which “Rosellinia necatrix partitivirus 11–Rosellinia necatrix partitivirus 25” were proposed, and 5 previously reported species. The newly identified partitiviruses have been taxonomically placed in two genera, Alphapartitivirus, and Betapartitivirus. Some partitiviruses were transfected into reference strains of the natural host, R. necatrix, and an experimental host, Cryphonectria parasitica, using purified virions. A comparative analysis of resultant transfectants revealed interesting differences and similarities between the RNA accumulation and symptom induction patterns of R. necatrix and C. parasitica. Other interesting findings include the identification of a probable reassortment event and a quintuple partitivirus infection of a single fungal strain. These combined results provide a foundation for further studies aimed at elucidating mechanisms that underly the differences observed.

Highlights

Plant pathogenic fungi provide platforms for identifying eukaryotic viruses (Pearson et al, 2009; Xie and Jiang, 2014; Ghabrial et al, 2015; Suzuki, 2017; Hillman et al, 2018)
The remainder of the partitivirus isolates for which novel sequence information was obtained in this study were designated Rosellinia necatrix partitivirus 11–25 (RnPV11–RnPV25) (Table 2)
Pairwise comparisons of proteins encoded by new partitiviruses revealed moderate levels of amino acid sequence identity among RNA-dependent RNA polymerase (RdRP) and capsid protein (CP) (Supplementary Figure S3). These results indicated that the 15 partitiviruses that were newly identified belong to new species, which were named Rosellinia necatrix partitivirus 11 to Rosellinia necatrix partitivirus 25

Summary

Introduction

Plant pathogenic fungi provide platforms for identifying eukaryotic viruses (Pearson et al, 2009; Xie and Jiang, 2014; Ghabrial et al, 2015; Suzuki, 2017; Hillman et al, 2018). Studies involving particular fungal-viral systems have provided interesting insights into virus-virus and virus-host interactions (Cho et al, 2013; Jiang et al, 2013; Xie and Jiang, 2014; Hillman et al, 2018). Among fungal hosts commonly used for the study of viruses is the phytopathogenic ascomycete fungus, Rosellinia necatrix, which infects over 400 plant species and causes white root rot in perennial crops worldwide, and in Japan (Pliego et al, 2012; Kondo et al, 2013b). A survey of over 1,000 field isolates showed that ∼20% of field isolates harbor diverse populations of viruses

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Conclusion