Molecular characterization and In Vitro synthesis of infectious RNA of a Turnip vein-clearing virus isolated from Alliaria petiolata in Hungary.

A tobamovirus was isolated from leaves of Alliaria petiolata plants, showing vein-clearing, interveinal chlorosis, and moderate deformation. Host range experiments revealed a high similarity of isolate ApH both to ribgrass mosaic viruses and turnip vein-clearing viruses. The complete nucleotide sequence of the viral genome was determined. The genomic RNA is composed of 6312 nucleotides and contains four open reading frames (ORF). ORF1 is 3324 nt-long and encodes a polypeptide of about 125.3 kDa. The ORF1 encoded putative replication protein contains an Alphavirus-like methyltransferase domain. ORF2 is 4806 nt-long and encodes a polypeptide of about 182 kDa. The ORF2 encoded putative replication protein contains an RNA-dependent RNA polymerase, catalytic domain. ORF3 encodes the putative cell-to-cell movement protein with a molecular weight of 30.1 kDa. ORF4 overlaps with ORF3 and encodes the coat protein with a size of 17.5 kDa. Sequence comparisons revealed that the ApH isolate has the highest similarity to turnip vein-clearing viruses and should be considered an isolate of Turnip vein-clearing virus (TVCV). This is the first report on the occurrence of TVCV in Hungary. In vitro transcripts prepared from the full-length cDNA clone of TVCV-ApH were highly infectious and induced typical symptoms characteristic to the original isolate of the virus. Since infectious clones of TVCV-ApH and crTMV (another isolate of TVCV) markedly differed in respect to recovery phenotype in Arabidopsis thaliana, it is feasible to carry out gene exchange or mutational studies to determine viral factors responsible for the symptom recovery phenotype.

Molecular characterization of a beet ringspot nepovirus isolated from Begonia ricinifolia in Hungary.

A nepovirus was isolated from Begonia ricinifolia showing chlorotic ringspot and line pattern symptoms. The purified virus had spherical particles of ca. 30 nm and contained a single coat protein subunit of ca. 56 kDa. The complete nucleotide sequence of the bipartite viral genome was determined. RNA 1 is 7394 nucleotides long, flanked by 5' and 3' untranslated regions (UTR), and followed by a 3' poly-A tail. It contains a single 6810 nt long open reading frame (ORF), which is translated into a 255 kDa polyprotein composed of 2269 amino acids. The 4684 nt long RNA 2 has a 4053 nt long ORF which encodes a single polyprotein of 1350 amino acids with a molecular weight of 149 kDa. Sequence comparisons revealed that the virus isolated from B. ricinifolia has the highest sequence similarity to beet ringspot virus and should be considered as a strain of BRSV. This is the first report on the occurrence of BRSV in B. ricinifolia and the presence of this virus outside Scotland.