title: Detection and characterization of spontaneous internal deletion mutants of Beet Necrotic yellow vein virus RNA3 from systemic host Nicotiana benthamiana.
abstract: BACKGROUND
  Beet Necrotic Yellow Vein virus (BNYVV) is a member of the genus Benyvirus causing a worldwide sugar beet disease rhizomania. BNYVV contains four or five plus-sense single stranded RNAs. In altered selective conditions, multipartite RNA viruses of plant are prone to undergoing internal deletions, thus turning into Defective RNAs (D RNAs). Although several D RNAs have been reported in BNYVV infection, the spontaneous internal deletion mutants responsible for severe symptom in systemic host Nicotiana benthamiana (N. benthamiana) are not described so far.
  
  
  RESULTS
  Systemic host N. benthamiana was inoculated by Chinese BNYVV isolates. RT-PCR and Northern blot showed that the D RNAs forms of BNYVV RNA3 were present in the systemic infection of the N. benthamiana. Three distinct D-RNA3s, named as D-RNA 3α, D-RNA 3β and D-RNA 3γ, were made into infectious clones. When inoculated on the N. benthamiana, the in vitro transcripts of D forms exhibited more stable than that of wild-type RNA3 in systemic movement. Among the detected mutant, the p25 protein frame-shift mutant (D-RNA3α) induced obvious necrotic lesions on Tetragonia.expansa (T. expansa) and pronounced systemic symptom on the N. benthamiana. The D-RNA3α was further mutated artificially to pre-terminate the downstream N protein, leading to the abolishment of the pathogenicity, indicating the N protein was responsible for the necrotic symptom.
  
  
  CONCLUSIONS
  Our studies demonstrated the internal deletion mutants of BNYVV-RNA3 were spontaneously generated in the systemic infection on N. benthamiana. The internal deletions didn't affect the efficient replication of D-RNA3s, instead by improving the stability and pathogenicity of RNA3 in the systemic host N. benthamiana. Besides, our results also suggested the downstream N protein of RNA3, but not the upstream p25 protein, may play an important role in the systemic infection on N. benthamiana.
authors: State Key Laboratory for Agro-biotechnology and Ministry of Agriculture Key Laboratory for Plant Pathology, China Agricultural University, Beijing 100193, PR China.
authors: Ying
authors: Y
authors: Wang
authors: Huiyan
authors: H
authors: Fan
authors: Xian-Bing
authors: XB
authors: Wang
authors: Min
authors: M
authors: Li
authors: Chenggui
authors: C
authors: Han
authors: Dawei
authors: D
authors: Li
authors: Jialin
authors: J
authors: Yu
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D027461:Beta vulgaris; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000821:virology; D010942:Plant Viruses / Q000235:genetics* / Q000302:isolation & purification* / Q000472:pathogenicity; D012328:RNA Viruses / Q000235:genetics* / Q000302:isolation & purification* / Q000472:pathogenicity; D012367:RNA, Viral / Q000235:genetics*; D017384:Sequence Deletion; D014026:Nicotiana / Q000821:virology*; D014764:Viral Proteins / Q000235:genetics; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics; D014779:Virus Replication
chemical_list: D012367:RNA, Viral; D014764:Viral Proteins; D037521:Virulence Factors