Conserved and variable elements in RNA genomes of potexviruses

Abstract

The nucleotide sequences of genomic RNAs and predicted amino acid sequences of two strains of potato virus X and white clover mosaic potexvirus were compared to each other, and the proteins of different plus-RNA-containing plant viruses. The predicted non&ion proteins of potexviruses have direct sequence homology and common structural peculiarities with those of several 'Sindbis-like' plant viruses. The most conserved amino acid sequences were found to be located in the polypeptide encoded by the long S-proximal open reading frame (ORFl). The putative polypeptide encoded by the 0RF2 starting beyond the ORFl stop codon is clearly related to the presumptive NTP-binding domain of the ORFl-coded polypeptide. These results suggest possible functions for all of the potexvirus proteins and also indicate that potexviruses have a genome organization which is considerably different from that of other plant viruses.

The entire nucleotide sequence of foxtail mosaic virus RNA

“…A subgenomic message initiating at this location would have a size of 2.0 kb which corresponds to the experimental value of 1-9 kb (Mackie et al, 1988). The sequence GUUAGG located immediately upstream to the identified and deduced 5' ends for FMV sgRNAs is similar to putative 'promoter' sequences (Skryabin et al, 1988b;Sit et al, 1990;. Sequences similar to those at the 5' ends of the subgenomic RNAs are also found near the 5' termini of the gRNA in FMV, WC1MV and PMV but are less compelling in the other potexviruses.…”

“…The C-terminal domain of FMV ORFI contains both the NTP-binding helicase consensus sequence (Gorbalenya et al, 1988;Hodgman, 1988) and the RNA-dependent RNA polymerase consensus motif (Argos, 1988) (Fig. 2), as reported for other potexviruses (Skryabin et al, 1988b). These motifs are well conserved not only in potexviruses but also in most positive-strand RNA plant viruses (Habili & Symons, 1989).…”

“…NTP-binding helicase motif, located at the N terminus as in other potexviruses (Skryabin et al, 1988b). The remainder of ORF2 sequences from all other potexviruses are less related to each other than are ORF1 and ORF3 (IlK protein) sequences (Table 3; see also Zuidema et al, 1989).…”

“…The remainder of ORF2 sequences from all other potexviruses are less related to each other than are ORF1 and ORF3 (IlK protein) sequences (Table 3; see also Zuidema et al, 1989). FMV ORF 3 and ORF 4 are related to those of other potexviruses in that they contain stretches of hydrophobic residues predicted to form transmembrane helices (Morozov et al, 1987;Forster et al, 1988;Skryabin et aL, 1988b) bordered by charged residues. Although FMV has the smallest ORF4 of all potexviruses, the common N-terminal hydrophobic region is conserved.…”

Molecular characterization and field survey of Iranian potato virus X isolates

“…ORFs 2-4 are known as the triple gene block (TGB), encoding three polypeptides of 25, 12, and 8 kDa, respectively and are involved in viral movement [16,24]. The TGB proteins are highly conserved in members of the genera Potexvirus, Hordeivirus, Benyvirus and Carlavirus [6,15,23]. ORF5 encodes the capsid protein (CP) with an estimated molecular mass of 25 kDa and plays an significant role in cell-to-cell movement of PVX particles and translational regulation of the PVX RNA genome [10,14].…”