Abstract
Plum pox virus (PPV) causes the most economically-devastating viral disease in Prunus species. Unfortunately, few natural resistance genes are available for the control of PPV. Recessive resistance to some potyviruses is associated with mutations of eukaryotic translation initiation factor 4E (eIF4E) or its isoform eIF(iso)4E. In this study, we used an RNA silencing approach to manipulate the expression of eIF4E and eIF(iso)4E towards the development of PPV resistance in Prunus species. The eIF4E and eIF(iso)4E genes were cloned from plum (Prunus domestica L.). The sequence identity between plum eIF4E and eIF(iso)4E coding sequences is 60.4% at the nucleotide level and 52.1% at the amino acid level. Quantitative real-time RT-PCR analysis showed that these two genes have a similar expression pattern in different tissues. Transgenes allowing the production of hairpin RNAs of plum eIF4E or eIF(iso)4E were introduced into plum via Agrobacterium-mediated transformation. Gene expression analysis confirmed specific reduced expression of eIF4E or eIF(iso)4E in the transgenic lines and this was associated with the accumulation of siRNAs. Transgenic plants were challenged with PPV-D strain and resistance was evaluated by measuring the concentration of viral RNA. Eighty-two percent of the eIF(iso)4E silenced transgenic plants were resistant to PPV, while eIF4E silenced transgenic plants did not show PPV resistance. Physical interaction between PPV-VPg and plum eIF(iso)4E was confirmed. In contrast, no PPV-VPg/eIF4E interaction was observed. These results indicate that eIF(iso)4E is involved in PPV infection in plum, and that silencing of eIF(iso)4E expression can lead to PPV resistance in Prunus species.
Highlights
Plum pox virus (PPV) causes disease in Prunus trees, including peaches, plums, apricots, cherries and ornamental species
The involvement of eukaryotic translation initiation factor 4E (eIF4E) and/or eIF(iso)4E in potyvirus infections has been reported in several plant species, including Arabidopsis thaliana, lettuce, pepper and pea [29,31,32,42]. eIF4E and/or eIF(iso)4E were identified as susceptibility factors required for infection of cucumoviruses [43], bymoviruses [44] and carmoviruses [45]
The results indicated that silencing of eIF(iso)4E but not eIF4E provided effective resistance to PPV in Prunus species
Summary
Plum pox virus (PPV) causes disease in Prunus trees, including peaches, plums, apricots, cherries and ornamental species. The interaction between eIF(iso)4E and VPg correlates with potyvirus infectivity and the abolishment of this interaction can lead to virus resistance [30,41]. The involvement of eIF4E and/or eIF(iso)4E in potyvirus infections has been reported in several plant species, including Arabidopsis thaliana, lettuce, pepper and pea [29,31,32,42]. The results indicated that silencing of eIF(iso)4E but not eIF4E provided effective resistance to PPV in Prunus species. This is the first report confirming the involvement of eIF(iso)4E in PPV infection in its natural woody host
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