Characterization of a Novel Polerovirus Infecting Maize in China.

Sha Chen,Xueping Zhou,Guangzhuang Jiang,Yajuan Qian,Yong Liu,Jianxiang Wu

doi:10.3390/v8050120

Abstract

A novel virus, tentatively named Maize Yellow Mosaic Virus (MaYMV), was identified from the field-grown maize plants showing yellow mosaic symptoms on the leaves collected from the Yunnan Province of China by the deep sequencing of small RNAs. The complete 5642 nucleotide (nt)-long genome of the MaYMV shared the highest nucleotide sequence identity (73%) to Maize Yellow Dwarf Virus-RMV. Sequence comparisons and phylogenetic analyses suggested that MaYMV represents a new member of the genus Polerovirus in the family Luteoviridae. Furthermore, the P0 protein encoded by MaYMV was demonstrated to inhibit both local and systemic RNA silencing by co-infiltration assays using transgenic Nicotiana benthamiana line 16c carrying the GFP reporter gene, which further supported the identification of a new polerovirus. The biologically-active cDNA clone of MaYMV was generated by inserting the full-length cDNA of MaYMV into the binary vector pCB301. RT-PCR and Northern blot analyses showed that this clone was systemically infectious upon agro-inoculation into N. benthamiana. Subsequently, 13 different isolates of MaYMV from field-grown maize plants in different geographical locations of Yunnan and Guizhou provinces of China were sequenced. Analyses of their molecular variation indicate that the 3′ half of P3–P5 read-through protein coding region was the most variable, whereas the coat protein- (CP-) and movement protein- (MP-)coding regions were the most conserved.

Highlights

The family Luteoviridae belongs to the picornavirus-like superfamily of positive-strand RNA viruses [1] and currently includes three genera (Luteovirus, Polerovirus, and Enamovirus)
The protein encoded by ORF0 has been shown to function as an RNA-silencing suppressor (RSS) [7,8,9], which is distinct from the members of genus Luteovirus that lack ORF0 [10]
We have found a bias toward the identity of the first 51 -nucleotide of the Maize Yellow Mosaic Virus (MaYMV) vsiRNAs, in accord with the role played by this nucleotide in recruiting of small interfering RNAs (siRNAs) into specific AGO complexes [52,53]

Summary

Introduction

The family Luteoviridae belongs to the picornavirus-like superfamily of positive-strand RNA viruses [1] and currently includes three genera (Luteovirus, Polerovirus, and Enamovirus). The plant viruses in the genus Polerovirus possess monopartite RNA genomes of about 5–6 kb in length [2] that typically contain six open reading frames (ORF) referred to as ORF0 to ORF5, and three untranslated regions (UTRs), including the 51 UTR, the 31 UTR, and the intergenic UTR between ORF2 and ORF3 [3,4,5,6]. The protein encoded by ORF0 has been shown to function as an RNA-silencing suppressor (RSS) [7,8,9], which is distinct from the members of genus Luteovirus that lack ORF0 [10]. The protein encoded by ORF3a was reported to be required for long-distance movement of the virus in the plant [16]

Methods

Results

Discussion

Conclusion