Sclerotinia minor endornavirus 1, a novel pathogenicity debilitation-associated mycovirus with a wide spectrum of transmissibility

Authors: YANG, DAN - Huazhong Agricultural University; WU, MINGDE - Huazhong Agricultural University; ZHANG, JING - Huazhong Agricultural University; Chen, Weidong; LI, GUOQING - Huazhong Agricultural University; YANG, LONG - Huazhong Agricultural University

Submitted to: mBio
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/26/2018
Publication Date: 10/27/2018
Citation: Yang, D., Wu, M., Zhang, J., Chen, W., Li, G., Yang, L. 2018. Sclerotinia minor endornavirus 1, a novel pathogenicity debilitation-associated mycovirus with a wide spectrum of transmissibility. mBio. 10(11):589. https://doi.org/10.3390%2Fv10110589.
DOI: https://doi.org/10.3390%2Fv10110589

Interpretive Summary: Sclerotinia minor, a sister species of Sclerotinia sclerotiorum, causes Sclerotinia blight on a number of economically important crops. Understanding the biology of S. minor will help us better understand the biology of the more ubiquitous species S. sclerotiorum. This study investigated a unique virus named SmEV1 present in the strain LC22 of S. minor. Through a series of biological and molecular characterization, the virus SmEV1 was found to have a genome of 12,626 bp long that coded for a single protein. Its genome has all the features of endornaviruses. The virus SmEV1 reduces the virulence of its host fungus. It can even be transmitted to the fungus S. sclerotiorum through a special treatment. It is demonstrated that this mycovirus has potential as a biocontrol agent in protecting crops from infection by S. minor.

Technical Abstract: Sclerotinia minor is a phytopathogenic fungus causing sclerotinia blight on many economically important crops. Here we have characterized the biological and molecular properties of a novel endornavirus, Sclerotinia minor endornavirus 1 (SmEV1), isolated from the hypovirulent strain LC22 of S. minor. The genome of SmEV1 is 12,626 bp long with a single, large open reading frame (ORF) encoding for a putative protein of 4020 amino acids. The putative protein contains cysteine-rich region (CRR), viral methyltransferase (MTR), putative DEXDc, viral helicase (Hel), and RNA-dependent RNA polymerase (RdRp) domains. The putative protein and the conserved domains are phylogenetically related to endornaviruses. Hypovirulence and associated traits of strain LC22 and SmEV1 were readily transmitted horizontally via hyphal contact to isolates of different vegetative compatibility groups of S. minor. SmEV1 in strain LC22 was found capable of being transmitted vertically through sclerotia. Furthermore, SmEV1 can infect via PEG-mediated transfection and cause hypovirulence in S. sclerotiorum. SmEV1 enhanced resistance of S. minor to hydrogen peroxide, which was accompanied with up-regulated expression of catalase genes and cellular catalase activities, resulting in significantly reduced cellular H2O2 concentrations. Mycelium fragments of hypovirulent strain LC22 have a protective activity against attack by S. minor. Taken together, we concluded that SmEV1 is a novel pathogenicity debilitation-associated mycovirus with a wide spectrum of transmissibility, and has potential for biological control (virocontrol) of diseases caused by S. minor.