• The Plant Pathology Journal
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• 제39권1호
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• pp.28-38
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• 2023

Plant viruses are responsible for worldwide production losses of numerous economically important crops. The most common plant RNA viruses are positivesense single-stranded RNA viruses [(+)ss RNA viruses]. These viruses have small genomes that encode a limited number of proteins. The viruses depend on their host's machinery for the replication of their RNA genome, assembly, movement, and attraction to the vectors for dispersal. Recently researchers have reported that chloroplast proteins are crucial for replicating (+)ss plant RNA viruses. Some chloroplast proteins, including translation initiation factor [eIF(iso)4E] and 75 DEAD-box RNA helicase RH8, help viruses fulfill their infection cycle in plants. In contrast, other chloroplast proteins such as PAP2.1, PSaC, and ATPsyn-α play active roles in plant defense against viruses. This is also consistent with the idea that reactive oxygen species, salicylic acid, jasmonic acid, and abscisic acid are produced in chloroplast. However, knowledge of molecular mechanisms and functions underlying these chloroplast host factors during the virus infection is still scarce and remains largely unknown. Our review briefly summarizes the latest knowledge regarding the possible role of chloroplast in plant virus replication, emphasizing chloroplast-related proteins. We have highlighted current advances regarding chloroplast-related proteins' role in replicating plant (+)ss RNA viruses.

• Journal of Microbiology
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• 제34권1호
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• pp.61-67
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• 1996

Double-stranded RNA (dsRNA) viruses and single-stranded RNA(ssRNA) viruses were detected in a strain of Pleurotus mushroom cultivated in a farm. Those fungal virsus were purified in the pH 6.0 or pH 7.2 using CsCI or Cs$_{2}$SO$_{4}$ buoyant density centrifugation. Each viral particles were not completely separated at any trials. However, mushroom bacili-form virus contains a single major nucleic acid with 0.7 Kb ssRNA, which might code for 20 Kd viral capsid protein. The dsRNAs are encapsidatred into spherical-form viruses, whereas ssRNA viral genomes are encapsidated into two different sizes of bacili-form particles. A healthy-looking mushroom also contained some spherical-form viruses with dsRNAs. Laboratory strains of Pleurotus ostreatus and a cultivated strain of P. sajor-caju did not show any viral particles. Mushrooms with specific disease symptoms. however, contained at least four different sizes of spherical-form viruses. Thus, we concluded that a bacilli-form virus case a severe disease symptoms of adnormal on mushroom development.

• The Plant Pathology Journal
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• 제27권3호
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• pp.197-206
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• 2011

RNA silencing has had a large impact on biology in general, as well as on our understanding of plant-pathogen interactions, especially interactions between plants and viruses. While most of what we know about the mechanism of RNA silencing was deduced in the last 12 years, many of the interactions between plants and viruses, as well as virus-virus interactions in plants, which we now know are manifestations of RNA silencing, were the subject of decades of work from numerous laboratories. These laboratories were examining the nature and extent of phenomena such as recovery from infection, the formation of dark green islands resistant to re-infection, synergy between unrelated viruses and cross-protection between related viruses, all first described in the late 1920s. In this review, the relationships between these phenomena and their place in the defense mechanism we call RNA silencing will be described, to show how they are all linked.

• Research in Plant Disease
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• 제27권4호
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• pp.137-148
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• 2021

Plant RNA viruses are one of the most destructive pathogens that cause a significant loss in crop production worldwide. They have evolved with high genetic diversity and adaptability due to the short replication cycle and high mutation rate during genome replication, which are characteristics of RNA viruses. Plant RNA viruses exist as quasispecies with high genetic diversity; thereby, a rapid population transition with new fitness can occur due to selective pressure resulting from environmental changes. Plant resistance can act as selective pressure and affect the fitness of the virus, which may lead to the emergence of resistance-breaking variants. In this paper, we introduced the evolutionary perspectives of plant RNA viruses and the driving forces in their evolution. Based on this, we discussed the mechanism of the emergence of variant viruses that overcome plant resistance. In addition, strategies for deploying plant resistance to viral diseases and improving resistance durability were discussed.

• Korean Journal Plant Pathology
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• 제11권4호
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• pp.367-373
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• 1995

The cDNAs derived from the coat protein (CP) genes of six plant RNA viruses, tobacco mosaic virus-pepper strains (TMV-P) and -ordinary strain (TMV-OM), potato virus Y (PVY), turnip mosaic virus (TuMV), cucumber mosaic virus (CMV) and potato leafroll virus (PLRV), were subcloned into the transcription vector, pSPT18, containing SP6 and T7 promoters. The digoxigenin (DIG)-labeled RNA polymerase after linearlization of the cloned pSPTs with XbaI or SacI, and were tested for their sensitivities for the detection of the six viruses. In slot-blot hybridization, dilution end points for the detection of TMV-P and TMV-OM were 10-4, while those of PVY, TuMV and CMV were 10-3. PLRV was detected at the dilution of 10-2. When each RNA probe was applied for the detection of the viruses in the preparations from the leaf disks (8 mm in diameter, and 12 to 15 mg in weight) of infected natural host plants, TMV-P, TMV-OM and TuMV could be detected from one disk, while PVY from 1 or 2 disks. CMV was detected in the preparation from two disks, and PLRV from three disks. With DIG-labeled RNA probe, PVY was detected at 5 days after inoculation, but with ELISA the virus was detected at 8 days after inoculation to tobacco (Nicotiana tabacum cv. Xanthi nc) plants on which symptoms appeared at 9 days after inoculation. No difference was observed in cross reaction between the RNA probes for the detection of TMV-P and TMV-OM.

• The Plant Pathology Journal
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• 제21권1호
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• pp.13-20
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• 2005

Chlorella viruses are large icosahedral, plaque-forming, dsDNA viruses that infect certain unicellular, chlorellalike green algae. The genomic DNA of over 300 kb contains many useful genes and promoters. Over 40 chlorella viruses have been isolated from fresh water in Korea since 1998. The viruses were amplified initially in chlorella strain NC64A, and pure isolates were obtained by repeated plaque isolation. SDS-PAGE analysis revealed similar but distinct protein patterns, both among the group of purified viruses and in comparison with the prototype chlorella virus PBCV-1. Digestions of the 330- to 350-kb genomic DNAs with 10 restriction enzymes revealed different restriction fragment patterns among the isolates. The tRNA-coding regions of 8 chlorella viruses were cloned and sequenced. These viruses contain 14-16 tRNA genes within a 1.2- to 2-kb region, except for the SS-1 isolate, which has a 1039-bp spacer in a cluster of 11 tRNA genes. Promoter regions of several early genes were isolated and their activities were analyzed in transformed chlorella. Some promoters showed stronger activity than commonly used CaMV 35S promoter and chlorella transformation vectors for heterologous protein are beings constructed using these promoters.

• Korean Journal of Microbiology
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• 제43권4호
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• pp.285-291
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• 2007

According to the Baltimore Scheme, viruses are classified into 6 main classes based on their replication and coding strategies. Except for some small DNA viruses, most viruses code for their own polymerases: DNA-dependent DNA, RNA-dependent RNA and RNA-dependent DNA polymerases, all of which contain 4 common motifs. We undertook a phylogenetic study to establish the relationship between the Baltimore Scheme and viral polymerases. Amino acid sequence data sets of viral polymerases were taken from NCBI GenBank, and a multiple alignment was performed with CLUSTAL X program. Phylogenetic trees of viral polymerases constructed from the distance matrices were generally consistent with Baltimore Scheme with some minor exceptions. Interestingly, negative RNA viruses (Class V) could be further divided into 2 subgroups with segmented and non-segmented genomes. Thus, Baltimore Scheme for viral taxonomy could be supported by phylogenetic analysis based on the amino acid sequences of viral polymerases.

• Journal of Microbiology and Biotechnology
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• 제16권7호
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• pp.1017-1025
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• 2006

Hantaviruses possess three RNA segments of negative sense. Co-infection of closely related hantaviruses may result in generation of a progeny virus with genomic polyploidy, containing a partial or complete set of genome originated from more than one parental virus. To characterize the formation of viral genomic polyploidy, cultured Vero-E6 cells were co-infected with two closely related hantaviruses, Hantaan and Maaji, and the progeny viruses examined. The genotype of plaque-purified viruses was analyzed by a virus-specific RT-PCR. Seventy percent (67/96) of the progeny virus was categorized as Hantaan and 3.3% (2/96) was classified as Maaji, whereas 20% (21/96) was considered polyploidy as they contained both types of the S RNA segment. Most of the polyploidy progeny viruses were unstable and gave rise to either one of the parental viruses or a reassortant after several rounds of plaque purification. No recombination between the heterologous pair of S RNA was observed for those polyploid viruses during three consecutive plaque-to-plaque passages. These data suggest that the viral polyploidy formation constitutes a primary mechanism underlying the generation of a newly emerged hantavirus.

• The Plant Pathology Journal
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• 제38권3호
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• pp.220-228
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• 2022

Pollen is a vector for viral transmission. Pollenmediated viruses cause serious economic losses in the fruit industry. Despite the commercial importance of pollen-associated viruses, the diversity of such viruses is yet to be fully explored. In this study, we performed metatranscriptomic analyses using RNA sequencing to investigate the viral diversity in imported apple and kiwifruit pollen. We identified 665 virus-associated contigs, which corresponded to four different virus species. We identified one virus, the apple stem grooving virus, from pear pollen and three viruses, including citrus leaf blotch virus, cucumber mosaic virus, and lychnis mottle virus in kiwifruit pollen. The assembled viral genome sequences were analyzed to determine phylogenetic relationships. These findings will expand our knowledge of the virosphere in fruit pollen and lead to appropriate management of international pollen trade. However, the pathogenic mechanisms of pollen-associated viruses in fruit trees should be further investigated.

• Proceedings of the Korean Biophysical Society Conference
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• 한국생물물리학회 1999년도 학술발표회 진행표 및 논문초록
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• pp.37-37
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• 1999

The influenza A viruses which are the most severe and common among the influenza viruses have 8 segmented RNA genomes Each RNA segment has highly conserved 3' and 5' terminal sequence except a single U\longrightarrowC variation especially in the 4 position of the 3' terminal of the 3 segments encoding own RNA polymerase.(omitted)