Nucleotide sequence of shallot virus X RNA reveals a 5'-proximal cistron closely related to those of potexviruses and a unique arrangement of the 3'-proximal cistrons.

The 8890 nucleotide RNA sequence of shallot virus X (ShVX), a new virus isolated from shallot, has been determined. The sequence contains six open reading frames (ORFs) which encode putative proteins (in the 5' to 3' direction) of M(r) 194528 (ORF1), 26333 (ORF2), 11245 (ORF3), 42209 (ORF4), 28486 (ORF5) and 14741 (ORF6). The ORF1 protein was found to be highly homologous to the putative potexvirus RNA replicases; ORF2, -3, -5 and -6 proteins also have analogues among the potex- and/or carlavirus-encoded proteins. ORF3 is followed by an AUG-lacking frame coding for an amino acid sequence homologous to that of the 7K to 8K proteins of the triple gene block of the above-mentioned viruses. The putative ORF4 protein has no reliable homology with proteins in the database. The results obtained testify that, except for the unique 42K protein gene, the ShVX genome combines a number of elements typical of both carla- and potexviruses.