Unusual long-distance movement strategies of Potato mop-top virus RNAs in Nicotiana benthamiana.
The Potato mop-top virus (PMTV) genome encodes replicase, movement, and capsid proteins on three different RNA species that are encapsidated within tubular rod-shaped particles. Previously, we showed that the protein produced on translational readthrough (RT) of the coat protein (CP) gene, CP-RT, is associated with one extremity of the virus particles, and that the two RNAs encoding replicase and movement proteins can move long distance in the absence of the third RNA (RNA-CP) that encodes the capsid proteins, CP and CP-RT. Here, we examined the roles of the CP and CP-RT proteins on RNA movement using infectious clones carrying mutations in the CP and CP-RT coding domains. The results showed that, in infections established with mutant RNA-CP expressing CP together with truncated CP-RT, systemic movement of the mutant RNA-CP was inhibited but not the movement of the other two RNAs. Furthermore, RNA-CP long-distance movement was inhibited in a mutant clone expressing only CP in the absence of the CP-RT polypeptide. CP-RT was not necessary for particle assembly because virions were observed in leaf extracts infected with the CP-RT deletion mutants. RNA-CP moved long distance when protein expression was suppressed completely or when CP expression was suppressed so that only CP-RT or truncated CP-RT was expressed. CP-RT but not CP interacted with the movement protein TGB1 in the yeast two-hybrid system. CP-RT and TGB1 were detected by enzyme-linked immunosorbent assay in virus particles and the long-distance movement of RNA-CP was correlated with expression of CP-RT that interacted with TGB1; mutant RNA-CP expressing truncated CP-RT proteins that did not interact with TGB1 formed virions but did not move to upper noninoculated leaves. The results indicate that PMTV RNA-CP can move long distance in two distinct forms: either as a viral ribonucleoprotein complex or as particles that are most likely associated with CP-RT and TGB1.
Torrance
Lesley
L
Department of Plant Biology and Forest Genetics, Uppsala BioCenter SLU, Sweden.
Lukhovitskaya
Nina I
NI
Schepetilnikov
Mikhail V
MV
Cowan
Graham H
GH
Ziegler
Angelika
A
Savenkov
Eugene I
EI
D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D010935:Plant Diseases / Q000821:virology; D010942:Plant Viruses / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D012328:RNA Viruses / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D012367:RNA, Viral / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D017384:Sequence Deletion; D014026:Nicotiana / Q000821:virology*; D020798:Two-Hybrid System Techniques; D017361:Viral Nonstructural Proteins; D019065:Virus Assembly
D036022:Capsid Proteins; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D017361:Viral Nonstructural Proteins