Complete nucleotide sequence of a new potexvirus, 'Cnidium virus X', isolated from Cnidium officinale in Japan

Deciphering the virome of Chunkung (Cnidium officinale) showing dwarfism-like symptoms via a high-throughput sequencing analysis

BACKGROUND

Viruses have notable effects on agroecosystems, wherein they can adversely affect plant health and cause problems (e.g., increased biosecurity risks and economic losses). However, our knowledge of their diversity and interactions with specific host plants in ecosystems remains limited. To enhance our understanding of the roles that viruses play in agroecosystems, comprehensive analyses of the viromes of a wide range of plants are essential. High-throughput sequencing (HTS) techniques are useful for conducting impartial and unbiased investigations of plant viromes, ultimately forming a basis for generating further biological and ecological insights. This study was conducted to thoroughly characterize the viral community dynamics in individual plants.

RESULTS

An HTS-based virome analysis in conjunction with proximity sampling and a tripartite network analysis were performed to investigate the viral diversity in chunkung (Cnidium officinale) plants. We identified 61 distinct chunkung plant-associated viruses (27 DNA and 34 RNA viruses) from 21 known genera and 6 unclassified genera in 14 known viral families. Notably, 12 persistent viruses (7 DNA and 5 RNA viruses) were exclusive to dwarfed chunkung plants. The detection of viruses from the families Partitiviridae, Picobirnaviridae, and Spinareoviridae only in the dwarfed plants suggested that they may contribute to the observed dwarfism. The co-infection of chunkung by multiple viruses is indicative of a dynamic and interactive viral ecosystem with significant sequence variability and evidence of recombination.

CONCLUSIONS

We revealed the viral community involved in chunkung. Our findings suggest that chunkung serves as a significant reservoir for a variety of plant viruses. Moreover, the co-infection rate of individual plants was unexpectedly high. Future research will need to elucidate the mechanisms enabling several dozen viruses to co-exist in chunkung. Nevertheless, the important insights into the chunkung virome generated in this study may be relevant to developing effective plant viral disease management and control strategies.

Genetic diversity of viruses infecting cnidium plants (Cnidium officinale) in Japan

Cnidium vein yellowing virus (CnVYV), cnidium virus X (CnVX), cucumber mosaic virus (CMV) and cnidium virus 1 (CnV1) were detected at extremely high levels in Cnidium officinale plants showing viral symptoms collected from Iwate and Hokkaido Prefectures, Japan. The complete nucleotide sequence of the newly detected CnVYV and CnV1, and genetic diversity of the cnidium-infecting viruses (CnVYV, CnVX, and CnV1) indicated that South Korean and Japanese cnidium plants had close relationship with each other. All three viruses can infect vegetatively propagated perennials and are vertically transmitted once infection occurs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13337-023-00835-w.

Complete Genome Sequences of Two Apple Stem Grooving Viruses in Cnidium officinale in Korea

We determined the whole-genome sequences of two apple stem grooving viruses (ASGV) detected in infected Cnidium officinale plants. The analyzed ASGV genomes were 6,494 nucleotides long and encoded two overlapping open reading frames. Phylogenetic analysis revealed the two ASGV isolates to be most closely related to the ASGV isolate Xinjiang-3.

The N-Terminal α-Helix of Potato Virus X-Encoded RNA-Dependent RNA Polymerase Is Required for Membrane Association and Multimerization

Positive-sense single-stranded RNA viruses replicate in virus-induced membranous organelles for maximum efficiency and immune escaping. The replication of potato virus X (PVX) takes place on the endoplasmic reticulum (ER); however, how PVX-encoded RNA-dependent RNA polymerase (RdRp) is associated with the ER is still unknown. A proline-kinked amphipathic α-helix was recently found in the MET domain of RdRp. In this study, we further illustrate that the first α-helix of the MET domain is also required for ER association. Moreover, we found that the MET domain forms multimers on ER and the first α-helix is essential for multimerization. These results suggest that the RdRp of PVX adopts more than one hydrophobic motif for membrane association and for multimerization.

Complete genome sequence of cnidium closterovirus 1, a novel member of the genus Closterovirus infecting Cnidium officinale

The genome of a novel virus identified in Cnidium officinale is composed of a monopartite ssRNA of 16,755 nucleotides that shares 68.73% (query coverage, 20%) sequence identity with carrot yellow leaf virus (CYLV, accession no. FJ869862.1). It contains 11 putative open reading frames and has an organization typical of closteroviruses. It shares 30-50% nucleotide sequence identity with other closteroviruses. The heat shock protein 70-like protein (HSP70), putative RNA-dependent RNA polymerase (RdRp), and coat protein (CP) show 39-66%, 16-60%, and 24-41% amino acid sequence identity, respectively, to the homologous proteins of previously identified closteroviruses. Molecular and HSP70-based phylogenetic analysis of the genome and encoded protein sequences suggested that this virus is a novel member of the genus Closterovirus in the family Closteroviridae, which we have tentatively named "cnidium closterovirus 1" (CnClV1).