Disease relevance of Nepovirus

• In vitro processing of the RNA-2-encoded polyprotein of two nepoviruses: tomato black ring virus and grapevine chrome mosaic virus [1].
• The Arg/Gly cleavage site deduced by N-terminal amino acid sequence analysis is the first for a nepovirus coat protein and for plant viruses expressing their genomic RNAs by polyprotein synthesis [2].
• Cucumber mosaic cucumovirus (CMV) infection but not tomato black ring nepovirus infection counteracted post-transcriptional gene silencing (PTGS) of nitrate reductase (Nia) or beta-glucuronidase (uidA) transgenes in newly developing leaves of tobacco and Arabidopsis plants [3].
• The CP of cherry leaf roll nepovirus, whose virions are predominantly stabilised by protein-protein interactions did not bind even at the lowest salt concentration tested [4].

High impact information on Nepovirus

• Each ribozyme contained the conserved core bases of the hammerhead motif found in the positive strand of satellite RNA of tobacco ringspot virus [(+)sTRSV] and two stems, 7 and 8 bases long, complementary to the target, beta APP mRNA [5].
• This polyprotein is homologous with the protein encoded by the S strain of tomato black ring virus (TBRV) RNA2, the only other nepovirus sequenced so far [6].
• An additional plasmid was introduced in yeasts expressing the CIRV replicase, from which a defective interfering (DI) RNA (DI-7 RNA) could be transcribed under the control of the GAL1 promoter and terminated by the Tobacco ringspot virus satellite ribozyme, which cleaved 19 nucleotides downstream of the 3' end of DI RNA [7].
• Given the size of RNA2 and the presence of a long 3' non-coding region, SMoV is more typical of a nepovirus, although atypically for a nepovirus it is aphid transmissible [8].
• The proteinase of Tomato ringspot virus (genus Nepovirus) is responsible for proteolytic cleavage of the RNA2-encoded polyprotein (P2) at two cleavage sites, allowing definition of the domains for the movement protein (MP) and coat protein [9].

Chemical compound and disease context of Nepovirus

• The putative X1 protein contains a previously identified alanine-rich sequence which is present in nepoviruses but not in the related comoviruses [10].
• Effect of actinomycin D on replication of satellite tobacco ringspot virus RNA in plant protoplasts [11].
• Interestingly, this histidine residue is replaced by a leucine in the proteases of other sequenced nepoviruses [12].
• The grapevine fanleaf nepovirus 24K chymotrypsin-like cysteine proteinase, located between the VPg and the RNA polymerase in the RNA-1 encoded polyprotein P1, is active in its free form and in various precursors forms [13].
• Tomato ringspot nepovirus (TomRSV) RNA-1 encodes a putative NTP-binding protein (NTB), a putative viral genome-linked protein (VPg), a putative RNA-dependent RNA polymerase (Pol) and a serine-like protease (Pro), which have been suggested to be involved in viral RNA replication [14].

Biological context of Nepovirus

• These results raise the possibility that the presence of two distinct protein domains in the N-terminal part of the P1 polyprotein may be a common feature of nepoviruses [10].
• Genome organization of grapevine fanleaf nepovirus RNA2 deduced from the 122K polyprotein P2 in vitro cleavage products [15].
• Nucleotide sequence of black currant reversion associated nepovirus RNA1 [16].
• The coat protein (CP) was located in the C-terminal region of the large polyprotein and contained amino acid motifs conserved among nepovirus CPs [17].
• The RNA1 of black currant reversion associated nepovirus (BRAV) is 7711 nucleotides (nt) long, excluding the poly-A tail, and contains one long open reading frame (ORF) which is translated into a polyprotein of 2094 amino acids [16].

Gene context of Nepovirus

• Identification and map location of TTR1, a single locus in Arabidopsis thaliana that confers tolerance to tobacco ringspot nepovirus [18].
• An N-terminal domain of 350 amino acids of RNA2-encoded polyprotein shared 34 and 35% sequence identity with the N-terminal domains of tomato ringspot nepovirus RNA1- and RNA2-encoded polyproteins, respectively [17].
• Full-length cDNA clones corresponding to the RNA1 and RNA2 of the Polish isolate MJ of Tomato black ring virus (TBRV, genus Nepovirus) were obtained using a direct recombination strategy in yeast, and their complete nucleotide sequences were established [19].
• Tomato ringspot nepovirus RNA-1-encoded polyprotein (P1) contains the domains for the putative NTP-binding protein, VPg, 3C-like protease and a putative RNA-dependent RNA polymerase in its C-terminal region [10].
• SDV RNA2 does not contain the long (> 1300 nt) 3' non-coding region characteristic of some nepoviruses [20].

References