Comparison of the complete nucleotide sequences of two isolates of lettuce mosaic virus differing in their biological properties.
The complete nucleotide sequences of the genomic RNAs of the 0 and E isolates of lettuce mosaic potyvirus (LMV) have been determined. The genomes of these 2 isolates were 10 080 nucleotides (nt) in length, excluding the poly(A) tract, and encoded polyproteins of 3255 amino acids (aa). The open reading frame was flanked by a 5′ non-coding region of 103 nt and a 3′ non-coding region of 212 nucleotides. Ten proteins were predicted. The P3 protein, with 377 aa, was the longest potyviral P3 protein characterized to date, while the P1 protein, with 437 aa, was among the longest P1 proteins reported. Sequence comparisons between the 2 isolates demonstrated only limited sequence difference. The overall nucleotide and amino acid sequence identities between LMV-0 and LMV-E were 94 and 97% respectively. The greatest variability occurred in the P1 and in the variable N-terminal region of the coat protein, while the NIa protease domain, the NIb protein, the C-terminus of the helper component protease and the 3′ non-coding region were extensively conserved. While this sequence analysis did not allow direct identification of determinants involved in the resistant breaking or in the seed transmissibility properties, these data are a first step towards the characterization of these determinants.