Nucleotide Sequence of Potato Leafroll Luteovirus RNA

Abstract

SUMMARYA sequence of 5987 nucleotides is reported for the RNA of potato leafroll luteovirus (PLRV). The sequence contains six large open reading flames, and non-coding regions of 174 nucleotides at the 5' end, 141 nucleotides at the 3' end and 197 nucleotides between two large blocks of coding sequences. The 5' coding region encodes two polypeptides of 28 000 (28K) and 70K which overlap in different reading frames and circumstantial evidence suggests that the third open reading frame in the 5' block is translated by frameshift readthrough near the end of the 70K polypeptide to give a l18K polypeptide. The C-terminal part of the l18K protein contains the consensus sequence for RNA-dependent RNA polymerases. In vitro translation of PLRV RNA resulted in the synthesis mainly of 28K and 70K polypeptides and the largest product made was about 125K; these sizes are similar to those predicted for the translation products of the 5' block of coding sequence. The 3' block of coding sequence codes for three polypeptides: a 23K coat protein, a 17K polypeptide which is encoded in a different frame, and a 53K polypeptide which immediately follows the coat protein coding sequence, and is in the same reading frame. Circumstantial evidence suggests that the 53K polypeptide is translated by readthrough of the amber termination codon of the coat protein gene. The amino acid sequences encoded by the 3' block of coding sequence show many similarities with analogous polypeptides translated from the nucleotide sequences of RNA of barley yellow dwarf virus, PAV strain (BYDV) and,

The location of the 5' end of the potato leafroll luteovirus subgenomic coat protein mRNA

“…It is proposed that a core sequence occurs immediately upstream of the subgenomic RNA initiation site of BMV, and that this comprises some 20 bases and has regions of homology with the intercistronic sequences of other plant viruses (French & Ahlquist, 1987. Some of these features have been found in the intergenic non-coding region of PLRV RNA, in particular a U~A sequence followed by AAGA (Mayo et al, 1989). However, because it now appears that the subgenomic RNA initiation site is upstream of the intercistronic region, these features are actually downstream of the initiation point.…”

“…This discrepancy may reflect differences between either the length or the sequence of the subgenomic R N A of the two isolates. However, the published sequences of the isolates (Mayo et aL, 1989;Tacke et al, 1989) differ at only five nucleotides in the intergenic region. Moreover, we could find no evidence of a stop 40 nucleotides upstream of the coat protein initiation codon.…”

“…3b). We conclude that the subgenomic RNA starts at nucleotide 3376 (nucleotide 3481 in the sequence of Mayo et al, 1989). …”

“…The published sequence for the Scottish PLRV isolate (Mayo et al, 1989) contains a 5'-terminal sequence different from those of other isolates . Recent work has shown this sequence to be that of a minor fraction in the PLRV (Scottish) RNA .…”

“…Analysis of the nucleotide sequence of the genome of PLRV has identified six ORFs (Mayo et al, 1989;van der Wilk et al, 1989;Keese et al, 1990) which are thought to be expressed by a variety of strategies, including initiation at downstream AUG codons, shifting between reading frames during translation, suppression of termination codons and translation of subgenomic RNA containing downstream ORFs (Mayo et al, 1989;Bahner et al, 1990;Keese et al, 1990).…”