Virus-host interactions
-
Upload
vladimir-hughes -
Category
Documents
-
view
25 -
download
0
description
Transcript of Virus-host interactions
Virus-host interactions
-Strategies viruses use to replicate their genomes in susceptible host cells – “replication”
-Strategies viruses use to move their genomes throughout susceptible host plants – “cell-to-cell movement”
-Strategies viruses use to suppress host defenses
Plant viruses cause many different symptoms
Necrosis
Vein-banding
Little Cherry
Flower BreakingTissue Deformation
Viral Pathogenesis
Within the plant, viruses must complete three major steps in orderto infect a susceptible plant host.
Infection ofsingle cells
Cell-to-cellmovement
Long-distancemovement
Replication ReplicationMovement to adjacent cells
ReplicationMovement to adjacent cellsMovement to cells throughout the plant
Virus movement
After the virus replicates it has to be able to move to new cellsand new tissues/organs in order to systemically infect
Infection ofsingle cells
Cell-to-cellmovement
Long-distancemovement
Replication ReplicationMovement to adjacent cells
ReplicationMovement to adjacent cellsMovement to cells throughout the plant
Cell-to-cellmovement
ReplicationMovement to adjacent cells
Steps in cell-to-cell movement
1) Viruses need to leave sites of replication
2) Viruses need to locate the plasmodesmata
3) Viruses need to pass through plasmodesmata
Viral encoded “movement proteins (MPs)”facilitate these steps. Most MPs areMultifunctional.
1) MPs are required for movement
2) MPs bind to virus genomes
3) MPs interact with plant cytoskeleton
4) MPs localize to plasmodesmata
5) MPs gate plasmodesmata
Suppression of host defenses
Successful pathogens overcome innate host defense responses by targeting signaling, defense gene expression, or defense gene function.
-Suppression of RNA silencing
-Breaking throughthrough or breaking down physical or biochemical barriers
-Suppression (or modulation) of basal defense
-Suppression (or modulation) of (R gene–mediated HR or cell death)
The RNA silencing pathways – innate resistance to viruses
RNA silencing is logically an antiviral defense mechanism
Small RNAs corresponding to viruses can be found in infected tissues
Mutation of RNA silencing components can lead to increased virus infection
Viruses must protect themselves against this degradation pathway
Incarbone and Dunoyer. 2013. Trends Plant Sci.
Anti-viral RNA silencing and its supporession by plant viruses
Incarbone and Dunoyer. 2013. Trends Plant Sci.
Perturbation of miRNA pathways to enhance resistance or viral pathogenesis
Summary
- Plant viruses encode proteins that direct the replication and movement of their genomes
- Viral replication occurs in association with host membranes and host factors
- Viral movement is directed by movement proteins that serve many functions:binding the viral genometransporting the viral genome to plasmodesmatagating plasmodesmatatrafficking through plasmodesmata
- RNA silencingan antiviral defenseplant viruses encode suppressors of RNA silencing
RNA silencing suppressors function by a variety of mechanisms