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Virology. 2016 Nov;498:109-115. doi: 10.1016/j.virol.2016.08.014. Epub 2016 Aug 25.

Identification of the cleavage sites of the RNA2-encoded polyproteins for two members of the genus Torradovirus by N-terminal sequencing of the virion capsid proteins.

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Department of Plant Pathology, University of California, Davis, CA, 95616, USA.
CAPES Foundation, Ministry of Education of Brazil, Brasília-DF, Brazil.
Colegio de Postgraduados-Campus Montecillo, 56230 Texcoco, Mexico.
Department of Plant Pathology, University of California, Davis, CA, 95616, USA. Electronic address:


Torradoviruses, family Secoviridae, are emergent bipartite RNA plant viruses. RNA1 is ca. 7kb and has one open reading frame (ORF) encoding for the protease, helicase and RNA-dependent RNA polymerase (RdRp). RNA2 is ca. 5kb and has two ORFs. RNA2-ORF1 encodes for a putative protein with unknown function(s). RNA2-ORF2 encodes for a putative movement protein and three capsid proteins. Little is known about the replication and polyprotein processing strategies of torradoviruses. Here, the cleavage sites in the RNA2-ORF2-encoded polyproteins of two torradoviruses, Tomato marchitez virus isolate M (ToMarV-M) and tomato chocolate spot virus, were determined by N-terminal sequencing, revealing that the amino acid (aa) at the -1 position of the cleavage sites is a glutamine. Multiple aa sequence comparison confirmed that this glutamine is conserved among other torradoviruses. Finally, site-directed mutagenesis of conserved aas in the ToMarV-M RdRp and protease prevented substantial accumulation of viral coat proteins or RNAs.


Cleavage sites; N-terminal sequencing; Polyprotein; Torradovirus

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