Identification and Characterization of a Novel Emaravirus Associated With Jujube (Ziziphus jujuba Mill.) Yellow Mottle Disease

Caixia Yang; Song Zhang; Tong Han; Jingjing Fu; Francesco Di Serio; Mengji Cao

doi:10.3389/fmicb.2019.01417

Identification and Characterization of a Novel Emaravirus Associated With Jujube (Ziziphus jujuba Mill.) Yellow Mottle Disease

Front Microbiol. 2019 Jun 25:10:1417. doi: 10.3389/fmicb.2019.01417. eCollection 2019.

Authors

Caixia Yang¹, Song Zhang^{2

3}, Tong Han¹, Jingjing Fu¹, Francesco Di Serio⁴, Mengji Cao^{2

3}

Affiliations

¹ Liaoning Key Laboratory of Urban Integrated Pest Management and Ecological Security, College of Life Science and Engineering, Shenyang University, Shenyang, China.
² National Citrus Engineering and Technology Research Center, Citrus Research Institute, Southwest University, Chongqing, China.
³ Academy of Agricultural Sciences, Southwest University, Chongqing, China.
⁴ Istituto per la Protezione Sostenibile delle Piante, Consiglio Nazionale delle Ricerche, Bari, Italy.

Abstract

A previously unreported disease affecting jujube (Ziziphus jujuba Mill.) trees was observed in China (Liaoning province) in 2015 and named jujube yellow mottle disease (JYMD), due to prevalent symptoms on the leaves. Diseased plants produced also malformed and discolored fruits. In an attempt to identify the possible causal agent of JYMD, high-throughput sequencing of small RNA libraries was performed and a novel virus, tentatively named jujube yellow mottle-associated virus (JYMaV), was identified and characterized. Six genomic RNA segments of JYMaV were completely sequenced. Each one contains a single open reading frame in the viral complementary strand and two untranslated regions with complementary 5' and 3' terminal ends, thus showing typical features of other negative-stranded RNA viruses. RNA1 (7.1 kb), RNA2 (2.2 kb) and RNA3 (1.2 kb) encode putative proteins that, based on their conserved motifs, have been identified as the RNA dependent RNA polymerase, the glycoprotein and the nucleocapsid protein, respectively. These proteins share significant sequence identity (52.1-70.4%) with proteins encoded by raspberry leaf blotch virus (RLBV). RNA4 (1.5 kb) and RNA5 (1.2 kb) code for two putative 30 K movement proteins also related to the homologous RLBV protein. The functional role of the protein encoded by JYMaV RNA6 remains unknown. These data together with the phylogenetic relationships of JYMaV with other recognized emaraviruses support the proposal that JYMaV is the representative member of a novel species in the genus Emaravirus. In agreement with this proposal, virus-like particles and double-membrane-bound bodies, similar to those previously reported for other emaraviruses, were observed by transmission electron microscopy in extracts and tissues from symptomatic leaves, respectively. A specific RT-PCR-based detection method has been developed and used in a preliminary field survey that provided results strongly supporting the close association of JYMaV with the novel disease.

Keywords: Emaravirus; field survey; high-throughput sequencing; jujube (Ziziphus jujuba Mill.); phylogenetic relationship; transmission electron microscopy.