Tobacco veinal necrosis determinants are unlikely to be located within the 5′ and 3′ terminal sequences of the potato virus Y genome

Abstract

Three potato virus Y isolates, representatives of distinct PVY groups, identified in potato fields in northern Poland were submitted to biological and molecular analysis. Phenotypically, two isolates, PVYN-Ny and PVYN-Wi, belong to the necrotic strain and the third one (PVYO-LW) to the common strain. PVYN-Wi, however, did not react with monoclonal antibodies directed against the necrotic strain isolates which recognise PVYN-Ny. To characterise the isolates, coat protein genes were sequenced and compared with sequences from databases. The necrotic PVYN-Wi isolate showed 99% amino acid homology with the common one-PVYO-LW and significantly differed from the second necrotic isolate (PVYN-Ny). Sequence based homology matrix and phylogenetic analysis lead to classification of PVYN-Ny into group I, encompassing solely necrotic strain isolates, whereas PVYN-Wi falls into a phenotypically heterogeneous group II. The sequence analysis allowed for identification of putative group I-specific epitopes. 3'NTR (non-translated region) sequences were identical for PVYN-Wi and PVYO-LW. The 5'NTR, P1 gene, coat protein gene and 3'NTR sequences of the common (PVYO-LW) and the necrotic (PVYN-Wi) isolates are 99-100% homologous. This suggests that tobacco veinal necrosis determinants are located outside the 3' and 5' terminal sequences of the PVY genome.

Characterisation of potato virus Y isolates from Iran

“…Therefore, classification of potato isolates of PVY based on the 3 0 -UTR implies that this region cannot be used to demarcate strains of the isolates. Furthermore, it seems the unique 3 0 -UTR sequence of PVY is not related to the tuber or tobacco leaf necrosis symptoms, as also indicated by others [7,25]. One would expect there to be some level of correlation between the serology assays and CP sequences of PVY since the MAbs bind to the CP, however, as we have demonstrated in this paper, there is no direct correlation.…”

“…3, 4). Chachulska et al [7] also found high nucleotide homology (99-100%) between serology determined O-and N-strains in the 3 0 -UTR. Therefore, classification of potato isolates of PVY based on the 3 0 -UTR implies that this region cannot be used to demarcate strains of the isolates.…”

“…The ordinary or common strain (PVY O ) induces mild to severe mosaic and leaf drop streaks in potato, and systemic mottle in tobacco. The tobacco veinal necrosis (PVY N ) strain induces very mild mottling in most potato cultivars with occasional necrotic leaves in some cultivars [7,27], but induces severe systemic necrosis of leaf veins and petioles in tobacco [12].…”

“…We postulate that KER.SA N is a recombinant isolate with the PVY N -like recombinant region potentially between the region spanning the P1 and CP genes. Again, it is very clear that symptoms analysis does not directly correlate to correct strain identification.According to the sequence alignments of the CP gene, van der Vlugt et al[61] and Chachulska et al[7] described two main subgroups: subgroup I corresponds to strains carrying a glycine (G) at the CP N terminus and all are classified as necrotic (N) strains, while subgroup II corresponds to strains having an alanine (A) residue, most of which are classified as O strains. The PVY O Iranian isolates have the CP sequence starting by an alanine (A) and the Iranian isolates of PVY N and PVY NTN together carry a glycine (G) at the CP N-terminus.…”

Biological and molecular characterization of two tomato strains of potato virus Y (PVY)

“…Alignments were performed using the ALIGN program version 2.0, available on the INFOBIOGEN internet site (Myers & Miller 1989). Six PVY isolates representing O and N groups [used for phylogenetic studies by Revers et al (1996) and Chachulska et al(1997)] and two strains that have been completely sequenced, PVY-Canada (O) (Singh & Singh, 1996) and PVY-N605 (N) (Jakab et al 1997), were used in this analysis.…”