Discovery and Characterization of a Novel Carlavirus Infecting Potatoes in China.

Yuan-Yuan Li,Hesham Abouelnasr,Cheng-Gui Han,Hai-Ying Xiang,Jenifer Huang Mcbeath,Da-Wei Li,Ru-Nan Zhang,Jia-Lin Yu

doi:10.1371/journal.pone.0069255

Yuan-Yuan Li, Hesham Abouelnasr + Show 6 more

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https://doi.org/10.1371/journal.pone.0069255

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Abstract

A new carlavirus, tentatively named Potato virus H (PVH), was found on potato plants with mild symptoms in Hohhot, Inner Mongolia Autonomous Region, China. PVH was confirmed by genome sequencing, serological reactions, electron microscopy, and host index assays. The PVH particles were filamentous and slightly curved, with a modal length of 570 nm. Complete RNA genomic sequences of two isolates of PVH were determined using reverse transcription-PCR (RT-PCR) and the 5′ rapid amplification of cDNA ends (5' RACE) method. Sequence analysis revealed that PVH had the typical genomic organization of members of the genus Carlavirus, with a positive-sense single-stranded genome of 8410 nt. It shared coat protein (CP) and replicase amino acid sequence identities of 17.9–56.7% with those of reported carlaviruses. Phylogenetic analyses based on the protein-coding sequences of replicase and CP showed that PVH formed a distinct branch, which was related only distantly to other carlaviruses. Western blotting assays showed that PVH was not related serologically to other potato carlaviruses (Potato virus S, Potato virus M, and Potato latent virus). PVH systemically infected Nicotiana glutinosa but not Nicotiana tabacum, Nicotiana benthamiana , or Chenopodium quinoa , which is in contrast with the other potato carlaviruses. These results support the classification of PVH as a novel species in the genus Carlavirus. Preliminary results also indicated that a cysteine-rich protein encoded by the smallest ORF located in the 3' proximal region of the genome suppressed local RNA silencing and enhanced the pathogenicity of the recombinant PVX.

Highlights

Potato is one of the most important food crops in the world
During the detection of Potato leaf roll virus (PLRV) using reverse transcription-PCR (RT-PCR) with degenerate primers for poleroviruses, a much larger PCR product designated p1 (~3.4 kb rather than expected 1.6 kb) was obtained
The purified CPPVS, CPPVM, and positive control for PoLV reacted negatively to the polyclonal antiserum against CPPVH (Figure 3). These results show that Potato virus H (PVH) is not related serologically to other potato carlaviruses (PVS, Potato virus M (PVM), and PoLV)

Summary

Introduction

Potato production reached a record level of 374.38 million tons in 2011 and worldwide potato production has exceeded the growth in production of other major food commodities in developing countries, in Asia. With a record production of 88.35 million tons in 2011, China was the world’s largest potato-producing country (FAO, 2011). In addition to the well-studied potato viruses such as Potato virus X (PVX), Potato virus Y (PVY), and Potato leaf roll virus (PLRV), which cause severe symptoms and yield losses, Potato virus S (PVS) and Potato virus M (PVM) are common but produce mild symptoms, they adversely affect yield. Losses of 10–15% have been reported in individual plants from susceptible cultivars with PVS secondary infection, and the infected plants may yield a higher proportion of unmarketable small tubers. PVM and PVS both belong to the genus Carlavirus in the newly established family Betaflexiviridae [2]

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