title: N-terminal basic amino acid residues of Beet black scorch virus capsid protein play a critical role in virion assembly and systemic movement.
abstract: BACKGROUND
  Beet black scorch virus (BBSV) is a small single-stranded, positive-sense RNA plant virus belonging to the genus Necrovirus, family Tombusviridae. Its capsid protein (CP) contains a 13 amino acid long basic region at the N-terminus, rich in arginine and lysine residues, which is thought to interact with viral RNA to initiate virion assembly.
  
  
  RESULTS
  In the current study, a series of BBSV mutants containing amino acid substitutions as well as deletions within the N-terminal region were generated and examined for their effects on viral RNA replication, virion assembly, and long distance spread in protoplasts and whole host plants of BBSV. The RNA-binding activities of the mutated CPs were also evaluated in vitro. These experiments allowed us to identify two key basic amino acid residues in this region that are responsible for initiating virus assembly through RNA-binding. Proper assembly of BBSV particles is in turn needed for efficient viral systemic movement.
  
  
  CONCLUSIONS
  We have identified two basic amino acid residues near the N-terminus of the BBSV CP that bind viral RNA with high affinity to initiate virion assembly. We further provide evidence showing that systemic spread of BBSV in infected plants requires intact virions. This study represents the first in-depth investigation of the role of basic amino acid residues within the N-terminus of a necroviral CP.
authors.affiliation: State Key Laboratory of Agro-Biotechnology and Ministry of Agriculture Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Zhang
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Zhao
authors.forename: Yanjing
authors.initials: Y
authors.lastname: Zhang
authors.forename: Shaofang
authors.initials: S
authors.lastname: Niu
authors.forename: Feng
authors.initials: F
authors.lastname: Qu
authors.forename: Yongliang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Chenggui
authors.initials: C
authors.lastname: Han
authors.forename: Jialin
authors.initials: J
authors.lastname: Yu
authors.forename: Dawei
authors.initials: D
authors.lastname: Li
mesh_terms: D024361:Amino Acids, Basic / Q000235:genetics / Q000378:metabolism*; D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism*; D004252:DNA Mutational Analysis; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D010944:Plants / Q000821:virology*; D011485:Protein Binding; D012367:RNA, Viral / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D019183:Tombusviridae / Q000472:pathogenicity* / Q000502:physiology*; D019065:Virus Assembly
chemical_list: D024361:Amino Acids, Basic; D036022:Capsid Proteins; D050505:Mutant Proteins; D012367:RNA, Viral; D016601:RNA-Binding Proteins