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Title: Comparison of helper component-protease RNA silencing suppression activity, subcellular localization, and aggregation of three Korean isolates of Turnip mosaic virus

item HAN, JAE-YEONG - Chungnam National University
item CHUNG, JIN-SOO - Chungnam National University
item KIM, JUNG-KYU - Chungnam National University
item SEO, EUN-YOUNG - Chungnam National University
item KILCREASE, JAMES - Orise Fellow
item Bauchan, Gary
item LIM, SEUNG-MO - University Of Science And Technology Of China
item Hammond, John
item LIM, HYOUN-SUB - Chungnam National University

Submitted to: Virus Genes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2015
Publication Date: 6/30/2016
Citation: Han, J., Chung, J., Kim, J., Seo, E., Kilcrease, J.P., Bauchan, G.R., Lim, S., Hammond, J., Lim, H. 2016. Comparison of helper component-protease RNA silencing suppression activity, subcellular localization, and aggregation of three Korean isolates of Turnip mosaic virus. Virus Genes. 52:592-596.

Interpretive Summary: Radish is an important vegetable crop in Korea; virus infection causes losses of both yield and quality, and is therefore of concern to farmers. Knowing which viruses are present, how they are transmitted, and understanding differences in disease severity is important for developing control measures such as breeding virus-resistant varieties and controlling insects that may transmit the disease. Turnip mosaic virus (TuMV) is one of the most common viruses affecting radish and other members of the brassica family, including ornamental plants, and is found worldwide. Following a nationwide survey of TuMV in Korea, we discovered differences in a viral protein, but found that these differences were not correlated with disease severity. These results form the groundwork for further examination of isolates to identify factors that affect pathogenicity in various host species. This information can also be useful to plant breeders in selection of crops with improved resistance to TuMV.

Technical Abstract: In 2014, we performed a nationwide survey in Korean radish fields to investigate the distribution of Turnip mosaic virus (TuMV). Brassica chinensis sap-inoculated with TuMV-infected radish tissue showed different symptom severity with three isolates. In order to investigate variation among Korean TuMV isolates, we determined the full genome sequence of these three isolates. Sequence identities between genomic regions of isolates were 82.72-100% (nucleotide) and 88.12-100% (amino acid). A phylogenetic tree of TuMV genomic sequences showed that the three Korean isolates were clustered into the basal-BR group. The helper component protease (HC-Pro) proteins of these isolates were tested for their RNA silencing suppressor activity and subcellular localization in Nicotiana benthamiana. An RNA silencing suppression assay by co-agroinfiltration of HC-Pro with soluble-modified GFP (smGFP) showed that HC-Pro of isolate R007 and R041 showed stronger silencing suppressor activity than R065. The HC-Pros showed 98.25% amino acid identity, and weak silencing suppressor isolate (R065) has a single variant residue in the C-terminal domain associated with protease activity and self-interaction compared to isolates with strong silencing suppression activity. Formation of large subcellular aggregates of GFP:HC-Pro fusion proteins in N. benthamiana was only observed for HC-Pro from isolates with strong silencing suppression activity, suggesting that R065 ‘weak’ HC-Pro may have diminished self-association; substitution of the variant C-terminal residue largely reversed HC-Pro aggregation and silencing suppressor characteristics.