Beet Soil-Borne Virus RNA 3—A Further Example of the Heterogeneity of the Gene Content of Furovirus Genomes and of Triple Gene Block-Carrying RNAs

Abstract

The complete nucleotide sequence of RNA 3 of the Ahlum isolate of beet soil-borne virus (BSBV) was determined from cDNAs obtained with immunocaptured virus particles and denatured preparations of dsRNA. BSBV RNA 3 is unique among the plant virus RNAs studied so far in containing apparently only the coding sequences of a triple gene block (TGB). The derived amino acid sequences of the three putative TGB-encoded proteins showed the highest level of sequence similarities with those of the corresponding proteins of potato mop top furovirus (PMTV) followed by those of peanut clump furovirus and barley stripe mosaic hordeivirus. Progressively fewer similarities were found with the TGB-encoded proteins of beet necrotic yellow vein virus (uncertain classification), potato X potexvirus, and potato M carlavirus. The 3'-terminal 78 nucleotides of BSBV RNA 3 can be folded into a tRNA-like structure and a high degree of sequence similarity exists between the 122 3'-terminal nucleotides of BSBV RNA 3 and PMTV RNA 2. In other regions, however, no pronounced sequence similarities were found between the two RNAs, and PMTV RNA 2 contains an additional putative gene for a cysteine-rich protein downstream of the TGB. The two viruses are unrelated serologically. BSBV RNA 3 adds a further variant to the heterogeneity of the gene content of furovirus genomes and of triple gene block-carrying RNAs.

Evidence that the 37 kDa protein of Soil-borne wheat mosaic virus is a virus movement protein

“…The CP ORF has an opal translational termination codon and readthrough of this codon produces a large 84 kDa polypeptide (Hsu & Brakke, 1985). The CP readthrough domain (RT) is required for plasmodiophorid transmission of the virus (Koenig et al, 1997;Tamada & Kusume, 1991). The 39-proximal ORF of RNA2 encodes a 19 kDa polypeptide and its function is also not known.…”

A full-length infectious clone of beet soil-borne virus indicates the dispensability of the RNA-2 for virus survival in planta and symptom expression on Chenopodium quinoa leaves

“…Originally reported in Italy (Canova, 1959), rhizomania disease is now widespread in most countries where sugar beet is grown (McGrann et al, 2009) and BSBV is often found in beet infected with BNYVV (Meunier et al, 2003). However, the pathogenicity of BSBV and its contribution to the rhizomania syndrome remain unclear, with opinions still divided on this (Prillwitz & Schlösser, 1992;Kaufmann et al, 1993;Lindsten, 1993;Rush & Heidel, 1995).The BSBV genome consists of three single-stranded RNAs of positive polarity, packaged into rod-shaped particles (Koenig et al, 1996(Koenig et al, , 1997Koenig & Loss, 1997). RNA-1 (5.8 kb) encodes the putative viral replicase.…”

“…The BSBV genome consists of three single-stranded RNAs of positive polarity, packaged into rod-shaped particles (Koenig et al, 1996(Koenig et al, , 1997Koenig & Loss, 1997). RNA-1 (5.8 kb) encodes the putative viral replicase.…”

“…After total RNA extraction from sugar beet roots using the SV total RNA isolation kit (Promega), the three genomic RNAs were reverse transcribed and amplified by PCR (RT-PCR) using expand reverse transcriptase and the expand long template PCR System (Roche). Primers matching the extremities of the three viral RNAs were designed following the only references known to date (Koenig et al, 1996(Koenig et al, , 1997Koenig & Loss, 1997). Forward primers were flanked with a T7 promoter sequence (TAATACGACTCACTATAG) (Fig.…”

Characteristics of Beet Soilborne Mosaic Virus, a Furo-like Virus Infecting Sugar Beet

“…Natural variation in RNA length has been reported with BSBV (19), and genomic deletions in soilborne wheat mosaic virus, the type member of the genus Furovirus, can be caused by variations in air and/or soil temperatures at the time of sample collection (37). Because variation is common among members of the genus Furovirus, it is not surprising that we detected variation in the number and size of BSBMV RNA species.…”