Formation of virions is strictly required for turnip yellows virus long-distance movement in plants

C. Hipper, B. Monsion, D. Bortolamiol-Becet, V. Ziegler-Graff, V. Brault
2013 Journal of General Virology  
Viral genomic RNA of the Turnip yellows virus (TuYV; genus Polerovirus; family Luteoviridae) is protected in virions formed by the major capsid protein (CP) and the minor component, the readthrough (RT*) protein. Long-distance transport, used commonly by viruses to systemically infect host plants, occurs in phloem sieve elements and two viral forms of transport have been described: virions and ribonucleoprotein (RNP) complexes. With regard to poleroviruses, virions have always been presumed to
more » ... e the long-distance transport form, but the potential role of RNP complexes has not been investigated. Here, we examined the requirement of virions for polerovirus systemic movement by analysing CP-targeted mutants that were unable to form viral particles. We confirmed that TuYV mutants that cannot encapsidate into virions are not able to reach systemic leaves. To completely discard the possibility that the introduced mutations in CP simply blocked the formation or the movement of RNP complexes, we tested in trans complementation of TuYV CP mutants by providing WT CP expressed in transgenic plants. WT CP was able to facilitate systemic movement of TuYV CP mutants and this observation was always correlated with the formation of virions. This demonstrated clearly that virus particles are essential for polerovirus systemic movement. Turnip yellows virus (TuYV; genus Polerovirus; family Luteoviridae) has icosahedral virions of~25 nm of diameter that encapsidate the viral RNA genome. TuYV virions are composed of the major CP (23 kDa) and the minor component, the readthrough protein (RT* protein, 54 kDa), that arises from a C-terminal cleavage of the native product of 74 kDa (RT protein). The RT protein is a C-terminal extension of CP that is produced by a bypass of the CP stop codon. CP, RT* and RT proteins are involved in polerovirus long-distance transport (Brault et al., 2000, 3Present address: CNRS, IBMP, UPR 2357, 12 rue du Gé né ral Zimmer,
doi:10.1099/vir.0.058867-0 pmid:24214396 fatcat:54cm7mhcjfchbgz4miyez76pwm