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Biological and Molecular Characterization of a New Carlavirus Isolated from an Aconitum sp.

A new virus was isolated from symptomless Aconitum napellus plants. The virus, for which the name Aconitum latent virus (AcLV) is proposed, has flexuous particles 640 nm in length. The experimental host range was limited to Nicotiana clevelandii. Electron microscopy studies of ultrathin sections of infected A. napellus tissues revealed the presence of elongated virus particles. No inclusion bodies characteristic of potyvirus infection were observed. AcLV was purified from naturally infected A. napellus by cesium chloride step gradient centrifugation. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis of dissociated purified virus preparations, a major protein component with a molecular mass of 35 kDa was observed. Diagnostic antibodies that could specifically bind to virus particles were produced. The 5′ terminus (620 nucleotides) of the viral RNA was cloned and sequenced. It comprised 71 nucleotides from the untranslated 5′ terminus and 549 nucleotides of an open reading frame encoding 183 amino acids. Comparison of the predicted amino acid sequence with those of other plant viruses revealed 40 to 60% identity with several carlaviruses. Based on particle morphology, absence of inclusion bodies in ultrathin sections, the relative molecular weight of the coat protein, the nucleotide sequence, and predicted amino acid homology, it is suggested that this virus belongs to the carlavirus group.