A Novel Iflavirus Was Discovered in Green Rice Leafhopper Nephotettix cincticeps and Its Proliferation Was Inhibited by Infection of Rice Dwarf Virus.

Fei Wang,Yanyuan Bao,Qisheng Song,Yi Yang,Gongyin Ye,Xuefei Chang,Hongwei Yao,Jingjing Li,Wenxi Jia

doi:10.3389/fmicb.2020.621141

Abstract

The green rice leafhopper, Nephotettix cincticeps (Hemiptera: Cicadellidae), is a key insect vector transmitting rice dwarf virus (RDV) that causes rice dwarf disease. We discovered a novel iflavirus from the transcriptomes of N. cincticeps and named it as Nephotettix cincticeps positive-stranded RNA virus-1 (NcPSRV-1). The viral genome consists of 10,524 nucleotides excluding the poly(A) tail and contains one predicted open reading frame encoding a polyprotein of 3,192 amino acids, flanked by 5' and 3' untranslated regions. NcPSRV-1 has a typical iflavirus genome arrangement and is clustered with the members of the family Iflaviridae in the phylogenetic analysis. NcPSRV-1 was detected in all tested tissues and life stages of N. cincticeps and could be transmitted horizontally and vertically. Moreover, NcPSRV-1 had high prevalence in the laboratory populations and was widely spread in field populations of N. cincticeps. NcPSRV-1 could also infect the two-striped leafhopper, Nephotettix apicalis, at a 3.33% infection rate, but was absent in the zigzag leafhopper, Recilia dorsalis, and rice Oryza sativa variety TN1. The infection of RDV altered the viral load and infection rate of NcPSRV-1 in N. cincticeps, for which it seems that RDV has an antagonistic effect on NcPSRV-1 infection in the host.

Highlights

It has long been acknowledged that insects are important vectors and hosts of numerous viruses infecting humans, animals, and plants
The genome-like sequences were amplified with polymerase chain reaction (PCR) (Supplementary Figure S2) and rapid amplification of cDNA ends (RACE), sequenced, and named as NcPSRV-1
For the conserved motifs in VP1, especially motif I, II, and III, were missing among some viruses, the conserved motifs in VP1 we proposed in this work cannot be applied to every iflaviruses, but the missing parts of the motifs may provide some basis for the taxonomy of the genus Iflavirus

Summary

Introduction

It has long been acknowledged that insects are important vectors and hosts of numerous viruses infecting humans, animals, and plants. The iflaviruses are initially isolated from several economic insects, i.e., honey bees and silkworms, causing flacherie, malformations, and death of the infected insects (Isawa et al, 1998; Ghosh et al, 1999). Iflaviridae is a family classified under the order Picornavirales, comprising viruses with monopartite, single-stranded, positivesense, and non-segmented RNA genomes. Bat iflavirus is closely related to slow bee paralysis virus and the nucleotide composition analysis of the viral genome indicates that the iflavirus may have insect hosts (Yinda et al, 2017). It suggests that the iflaviruses found in bats feces might be diet derived from the infected insects (Yinda et al, 2017)

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Conclusion