title: Comparison of helper component-protease RNA silencing suppression activity, subcellular localization, and aggregation of three Korean isolates of Turnip mosaic virus.
abstract: In 2014, we performed a nationwide survey in Korean radish fields to investigate the distribution and variability of Turnip mosaic virus (TuMV). Brassica rapa ssp. pekinensis sap-inoculated with three isolates of TuMV from infected radish tissue showed different symptom severities, whereas symptoms in Raphanus sativus were similar for each isolate. The helper component-protease (HC-Pro) genes of each isolate were sequenced, and phylogenetic analysis showed that the three Korean isolates were clustered into the basal-BR group. The HC-Pro proteins of these isolates were tested for their RNA silencing suppressor (VSR) activity and subcellular localization in Nicotiana benthamiana. A VSR assay by co-agroinfiltration of HC-Pro with soluble-modified GFP (smGFP) showed that HC-Pro of isolate R007 and R041 showed stronger VSR activity than R065. The HC-Pros showed 98.25 % amino acid identity, and weak VSR isolate (R065) has a single variant residue in the C-terminal domain associated with protease activity and self-interaction compared to isolates with strong VSR 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 VSR activity, suggesting that R065 'weak' HC-Pro may have diminished self-association; substitution of the variant C-terminal residue largely reversed the HC-Pro aggregation and silencing suppressor characteristics. The lack of correlation between VSR efficiency and induction of systemic necrosis (SN) suggests that differences in viral accumulation due to HC-Pro are not responsible for SN.
authors.affiliation: Chungnam National University, Daejeon, Republic of Korea.
authors.forename: Jae-Yeong
authors.initials: JY
authors.lastname: Han
authors.affiliation: Chungnam National University, Daejeon, Republic of Korea.
authors.forename: Jinsoo
authors.initials: J
authors.lastname: Chung
authors.affiliation: Chungnam National University, Daejeon, Republic of Korea.
authors.forename: Jungkyu
authors.initials: J
authors.lastname: Kim
authors.affiliation: Chungnam National University, Daejeon, Republic of Korea.
authors.forename: Eun-Young
authors.initials: EY
authors.lastname: Seo
authors.affiliation: Floral and Nursery Plants Research Unit, USDA-ARS, USNA, Beltsville, MD, 20705, USA.
authors.forename: James P
authors.initials: JP
authors.lastname: Kilcrease
authors.affiliation: Electron and Confocal Microscopy Unit, USDA-ARS, BARC, Beltsville, MD, 20705, USA.
authors.forename: Gary R
authors.initials: GR
authors.lastname: Bauchan
authors.affiliation: Plant Systems Engineering Research Center, Korea Research Institute of Bioscience & Biotechnology, Daejeon, 305-806, Republic of Korea.|Biosystems and Bioengineering Program, University of Science and Technology, Daejeon, 305-350, Republic of Korea.
authors.forename: Seungmo
authors.initials: S
authors.lastname: Lim
authors.affiliation: Floral and Nursery Plants Research Unit, USDA-ARS, USNA, Beltsville, MD, 20705, USA. john.hammond@ars.usda.gov.
authors.forename: John
authors.initials: J
authors.lastname: Hammond
authors.affiliation: Chungnam National University, Daejeon, Republic of Korea. hyounlim@cnu.ac.kr.
authors.forename: Hyoun-Sub
authors.initials: HS
authors.lastname: Lim
mesh_terms: D029688:Brassica napus / Q000821:virology; D003546:Cysteine Endopeptidases / Q000235:genetics; D007723:Korea; D010447:Peptide Hydrolases / Q000235:genetics*; D010802:Phylogeny; D010935:Plant Diseases / Q000821:virology; D034622:RNA Interference / Q000502:physiology; D012367:RNA, Viral / Q000235:genetics*; D017806:Tymovirus / Q000235:genetics* / Q000302:isolation & purification*; D014764:Viral Proteins / Q000235:genetics
chemical_list: D012367:RNA, Viral; D014764:Viral Proteins; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; C072775:HC-Pro protein, potyvirus
keywords: Helper component-protease (HC-Pro); Pathogenicity; RNA silencing suppressor efficiency; Turnip mosaic virus