Michel Tribodet

Genomic variability in Potato potyvirus Y (PVY): evidence that PVYNW and PVYNTN variants are single to multiple recombinants between PVYO and PVYN isolates

Summary. Fourteen Potato virus Y (PVY) isolates representative of PVYO, PVYN, PVYNTN and PVYNW groups were characterised at genomic level. Restriction fragment length polymorphism study (RFLP) of each gene of these isolates and sequencing of the first 2700 nucleotides of two PVYNW isolates were performed. A mosaic structure was revealed in PVYNW and PVYNTN genomes, which showed either PVYO or PVYN-like sequences, depending on the particular gene. Indeed, starting from the 5′-end, these isolates showed a switching, from PVYN- to PVYO-like sequence, in the HC-Pro C-terminal region. Reversion to PVYN-like sequence was also revealed in the NIa N-terminal area of PVYNTN isolates, followed by a switching back to a PVYO-like sequence in the CP gene. Lastly, some PVYNW isolates showed a switching from PVYO- to PVYN-like sequence in the P1 N-terminal part, thus separating our PVYNW isolates into two subgroups. All these apparent recombination events were shown by statistical analysis. Comparison of molecular traits with pathogenic properties of our isolates suggested that the HC-Pro protein is involved in induction of necrosis in tobacco leaves, and the NIa, NIb and/or CP protein in necrosis in potato tubers. Nevertheless, multiple recombination events observed in the PVYNTN genome may play a role in the latter phenomenon.

Characterization of potato potyvirus Y (PVY) isolates from seed potato batches. Situation of the NTN, Wilga and Z isolates

AbstractA collection of 38 PVY isolates from seed potato batches, originating from several Western European countries, was characterized by using current biological, serological and molecular tools differentiating PVY strains and groups. The correlation between the three kinds of tests was good but not absolute. No single serological or PCR method was able to discriminate among the five isolate groups found. Twenty-nine isolates belonged to the PVYN strain and six to the PVYO strain. No PVYC was found. Two other isolates reacted serologically like PVYO, but were unable to elicit a hypersensitive response from the Nytbr gene and probably represent the PVYZ group. At the molecular level, these two isolates showed a combination of both PVYO and PVYN and could be recombinants of these strains. Another isolate reacted serologically like PVYO, but induced vein necrosis in tobacco, like PVYN-Wilga. Some PVYN isolates caused tuber ring necrosis in glasshouse conditions. These might belong to the PVYNTN group. The PVYNTN, PVYN-Wilga and PVYZ groups probably represent pathotypes within strains PVYN and PVYO, respectively. The present study also confirms previous reports showing a high genetic variation at the 5

RFLP mapping of the whole genome of ten viral isolates representative of different biological groups of potato virus Y.

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Fluorescently Tagged Potato virus Y: A Versatile Tool for Functional Analysis of Plant-Virus Interactions

end within the PVYN strain.

The amino acid 419 in HC-Pro is involved in the ability of PVY isolate N605 to induce necrotic symptoms on potato tubers

Based on the sequence polymorphism in the 5′ terminal part of the viral genome, a range of PVYN isolates were characterized by polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP). Three pairs of primers selected in the 5′ non-translated and P1 protein region were tested. Two of them yielded PCR products of about 1Kb from all isolates tested. Restriction analysis of the PCR products gave two distinct electrophoretic patterns, whichever of the three enzymes was used. In this way, the 18 isolates were separated into two easily identifiable subgroups. All tuber necrosing isolates (PVYNTN) were clustered in the same subgroup.

Erratum to: Incidence and Characterization of Potato Virus Y in Seed Potatoes in Tunisia

SummaryTen PVY isolates representative of four PVY groups (YN, YNTN, YN-W, Y O), differing by their ability to induce reactions of vein necrosis on tobacco and tuber necrosis on potato, were studied in order to research the regions of the viral genome involved in these necrosis phenomena. The whole genome of these isolates was amplified in two fragments (4 063 and 5 670 nucleotides) and was subjected to a restriction fragment length polymorphism (RFLP) study. In the first 4 063 nucleotides of the PVY genome, a phenetic analysis of RFLP data resulted in a clustering of our PVY isolates into three groups: PVYN isolates (group A); PVYNTN and PVYN-W isolates (group B) and PVYO isolates (group C). In the last 5 670 nucleotides, two groups were found: PVYN and PVYNTN isolates (group D) and PVYO and PVYN-W isolates (group E). From this clustering and the necrosing properties known for theseisolates, the tobacco necrosis determinants seem more likely located inthe 5′ than in the 3′ half part of the viral RNA, whereas it would be theopposite situation for the determinants of the necrosis on potato tubers.Moreover a recombination event seemed to have occurred in the genome ofthe PVYN-W isolates.

Variability of potato virus Y in potato crops in France.

Surveys were conducted of symptomatic potato plants in late season crops, from the major potato production regions in Northern Tunisia, for infection with six common potato viruses. The presence of Potato leafroll virus (PLRV), Potato virus Y (PVY), Potato virus X (PVX), Potato virus A (PVA), Potato virus S (PVS) and Potato virus M (PVM) was confirmed serologically with virus infection levels up to 5.4, 90.2, 4.3, 3.8, 7.1 and 4.8%, respectively. As PVY was prevalent in all seven surveyed regions, further biological, serological and molecular typing of 32 PVY isolates was undertaken. Only one isolate was shown to induce PVYO-type symptoms following transmission to tobacco and to react only against anti-PVYO-C antibodies. Typical vein necrosis symptoms were obtained from 31 samples, six of which reacted against both anti-PVYN and anti-PVYO-C antibodies showing they contained mixed isolates, while 25 of them reacted only with anti-PVYN antibodies. An immunocapture RT-PCR molecular test using a PVYNTN specific primer pair set in the 5’NTR/P1 genomic region and examination of recombinant points in three genomic regions (HC-Pro/P3, CI/NIa and CP/3’NTR) showed that all 25 serotype-N PVY isolates were PVYNTN variants with similar recombinations to the standard PVYNTN-H isolate. This is the first report of the occurrence of the PVYNTN variant and its high incidence in late season potatoes in Tunisia.

Specific detection of the PVYN-W variant of Potato virus Y

Potato virus Y (PVY) is an economically important plant virus that infects Solanaceous crops such as tobacco and potato. To date, studies into the localization and movement of PVY in plants have been limited to detection of viral RNA or proteins ex vivo. Here, a PVY N605 isolate was tagged with green fluorescent protein (GFP), characterized and used for in vivo tracking. In Nicotiana tabacum cv. Xanthi, PVY N605-GFP was biologically comparable to nontagged PVY N605, stable through three plant-to-plant passages and persisted for four months in infected plants. GFP was detected before symptoms and fluorescence intensity correlated with PVY RNA concentrations. PVY N605-GFP provided in vivo tracking of long-distance movement, allowing estimation of the cell-to-cell movement rate of PVY in N. tabacum cv. Xanthi (7.1 ± 1.5 cells per hour). PVY N605-GFP was adequately stable in Solanum tuberosum cvs. Désirée and NahG-Désirée and able to infect S. tuberosum cvs. Bintje and Bea, Nicotiana benthamiana, and wild potato relatives. PVY N605-GFP is therefore a powerful tool for future studies of PVY-host interactions, such as functional analysis of viral and plant genes involved in viral movement.Potato virus Y (PVY) is an economically important plant virus that infects Solanaceous crops such as tobacco and potato. To date, studies into the localization and movement of PVY in plants have been limited to detection of viral RNA or proteins ex vivo. Here, a PVY N605 isolate was tagged with green fluorescent protein (GFP), characterized and used for in vivo tracking. In Nicotiana tabacum cv. Xanthi, PVY N605-GFP was biologically comparable to nontagged PVY N605, stable through three plant-to-plant passages and persisted for four months in infected plants. GFP was detected before symptoms and fluorescence intensity correlated with PVY RNA concentrations. PVY N605-GFP provided in vivo tracking of long-distance movement, allowing estimation of the cell-to-cell movement rate of PVY in N. tabacum cv. Xanthi (7.1 ± 1.5 cells per hour). PVY N605-GFP was adequately stable in Solanum tuberosum cvs. Desiree and NahG-Desiree and able to infect S. tuberosum cvs. Bintje and Bea, Nicotiana benthamiana, and wild pot...