Modulation of host plant immunity by Tobamovirus proteins

To establish infections, plant viruses effect profound alterations to host physiology that disturb endogenous processes and contribute to the development of disease symptoms. Conti et al. summarise recently described effects of Tobacco Mosaic Virus on host plant physiology.

Schematic view of the proposed events associated with the replication and movement of TMV.
Schematic view of the proposed events associated with the replication and movement of TMV. (A) The early stage of the infection is determined by the entry of a viral particle into the symplast of a single cell, the disassembly of the virions and translation of the 126 and 183 kDa subunits of the replicase. Subsequently, negative strands and sub-genomic RNAs are synthesized to produce first the MP and then the CP. The accumulation of positive stranded viral RNAs and CPs permit the assembly of new viral particles. (B) The intermediate stages of infection are determined by the local spread of the viral RNAs between adjacent cells. The MP is implicated in facilitating the transport due to its ability to interact with plasmodesmata and bind RNA. (C) The late stages of infection are initiated when the virus reaches distant parts of the plants through vascular tissues and the infection becomes systemic. The systemic virus movement is facilitated by the CP by an incompletely understood mechanism. At this stage, the newly assembled viral particles can invade other plants by direct transmission.

This review focuses upon the non-canonical roles of viral proteins that bring about the modulation of host defence, through hormone imbalances, modulation of innate immunity and antiviral RNA silencing. The authors propose that a dynamic temporal and spatial scenario governs the Tobamovirus-host interaction with individual viral proteins acting in a concerted manner.

This paper is part of the Annals of Botany Special Issue on Plant Immunity. It will be free access till June 2017 and after April 2018.

Further reading

Conti, G., Rodriguez, M. C., Venturuzzi, A. L., & Asurmendi, S. (2016). Modulation of host plant immunity by Tobamovirus proteins. Annals of Botany, mcw216.