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Viruses rely completely on host translational machinery to produce the proteins encoded by their genes. Controlling translation initiation is important for gaining translational advantage in conflicts between the host and virus. The eukaryotic translation initiation factor 4E (eIF4E) has been reported to be hijacked by potyviruses for virus multiplication. The role of translation regulation in defence and anti‐defence between plants and viruses is not well understood. We report that the transcript level of eIF6 was markedly increased in turnip mosaic virus (TuMV)‐infected Nicotiana benthamiana. TuMV infection was impaired by overexpression of N. benthamiana eIF6 (NbeIF6) either transiently expressed in leaves or stably expressed in transgenic plants. Polysome profile assays showed that overexpression of NbeIF6 caused the accumulation of 40S and 60S ribosomal subunits, the reduction of polysomes, and also compromised TuMV UTR‐mediated translation, indicating a defence role for upregulated NbeIF6 during TuMV infection. However, the polysome profile in TuMV‐infected leaves was not identical to that in leaves overexpressing NbeIF6. Further analysis showed that TuMV NIb protein, the RNA‐dependent RNA polymerase, interacted with NbeIF6 and interfered with its effect on the ribosomal subunits, suggesting that NIb might have a counterdefence role. The results propose a possible regulatory mechanism at the translation level during plant–virus interaction. [ABSTRACT FROM AUTHOR]

Infection of viruses from the genera Bromovirus, Potyvirus, and Potexvirus in Nicotiana benthamiana induces significant up‐regulation of the genes that encode the HSP70 family, including binding immunoglobulin protein 2 (BiP2). Three up‐regulated genes were knocked down and infection assays with these knockdown lines demonstrated the importance of the BiP2 gene for potyvirus infection but not for infection by the other tested viruses. Distinct symptoms of cucumber mosaic virus (CMV) and potato virus X (PVX) were observed in the BiP2 knockdown line at 10 days postagroinfiltration. Interestingly, following inoculation with either soybean mosaic virus (SMV) or pepper mottle virus (PepMoV) co‐expressing green fluorescent protein (GFP), neither crinkle symptoms nor GFP signals were observed in the BiP2 knockdown line. Subsequent reverse transcription‐quantitative PCR analysis demonstrated that knockdown of BiP2 resulted in a significant decrease of SMV and PepMoV RNA accumulation but not PVX or CMV RNA accumulation. Further yeast two‐hybrid and co‐immunoprecipitation analyses validated the interaction between BiP2 and nuclear inclusion protein b (NIb) of SMV. Together, our findings suggest the crucial role of BiP2 as a proviral host factor necessary for potyvirus infection. The interaction between BiP2 and NIb may be the critical factor determining susceptibility in N. benthamiana, but further studies are needed to elucidate the underlying mechanism. [ABSTRACT FROM AUTHOR]

Potato virus Y (PVY) is the reason for significant losses in the potato crop yearly. The recent technologies in molecular biology have given insights on possibilities for control of viral infections at epigenetic level. In the present study, we obtained a DNA template complementary to a key sequence at the NIb genetic region of PVY. Potato leaves were inoculated with dsRNAs and siRNAs complementary to NIb 48 h before inoculation with PVY strain N/NTN. The treated plants did not develop any signs of disease. Double antibody sandwich еnzyme-linked immunosorbent assay (DAS-ELISA) of the plants treated with Nib-dsRNAs showed optical density values commensurate to the cut-off value. The Nib-siRNAs obtained in this study were twice as effective, with DAS-ELISA values which were below the cut-off and similar to the values of the healthy plants. Inducing posttranscriptional gene silencing in crops presents a promising utility for control of virus diseases and for prevention of crop losses, being non-inheritable, non-toxic and adaptable to a specific crop. [ABSTRACT FROM AUTHOR]

Potyviruses represent the largest group of known plant RNA viruses and include many agriculturally important viruses, such as Plum pox virus, Soybean mosaic virus, Turnip mosaic virus, and Potato virus Y. Potyviruses adopt polyprotein processing as their genome expression strategy. Among the 11 known viral proteins, the nuclear inclusion protein b (NIb) is the RNA-dependent RNA polymerase responsible for viral genome replication. Beyond its principal role as an RNA replicase, NIb has been shown to play key roles in diverse virus–host interactions. NIb recruits several host proteins into the viral replication complexes (VRCs), which are essential for the formation of functional VRCs for virus multiplication, and interacts with the sumoylation pathway proteins to suppress NPR1-mediated immunity response. On the other hand, NIb serves as a target of selective autophagy as well as an elicitor of effector-triggered immunity, resulting in attenuated virus infection. These contrasting roles of NIb provide an excellent example of the complex co-evolutionary arms race between plant hosts and potyviruses. This review highlights the current knowledge about the multifunctional roles of NIb in potyvirus infection, and discusses future research directions. [ABSTRACT FROM AUTHOR]