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第19回みちのくウイルス塾
植物ウイルスからみた宿主-ウイルスの相互作⽤
〜ウイルスと植物の共存と攻防〜
東北⼤学 農学研究科
⾼ 橋 英 樹
2020年7⽉23⽇(⽊)〜7⽉24⽇(⾦) 仙台医療センター・ウイルスセンター
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1. Differences and similarities of immune system between plants and animals 2. Acute infection with plant viruses 3. “Virus latency and the impact on plants”
Contents
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Plants and animals are both kingdoms of living things. They differ in important aspects. The chart below summarizes some of these differences.
How Plants and Animals Differ ?
PLANTS ANIMALS
Plants are generally rooted in one place and do not move on their own.
Most animals have the ability to move fairly freely.
Plants contain chlorophyll and can make their own food
Animals cannot make their own food and are dependent on plants and other animals for food.
Plants give off oxygen and take in carbon dioxide given off by animals.
Animals give off carbon dioxide which plants need to make food and take in oxygen which they need to breathe.
Plants have either no or very basic ability to sense.
Animals have a much more highly developed sensory and nervous system.
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Difference between Plant and Animal CellsPlant and animal cells are both eukaryotic cells. However, there are distinct properties between the cells found in plants and those found in animals under a light microscope. Below is a list of the major differences:
PLANTCELLS ANIMALCELLS
Hasacellwall,regularinshape Doesnothaveacellwall,irregularinshape
Chloroplastpresent Nochloroplastpresent
Largevacuoleslocatedinthecenterofthecell Smalltemporaryvacuolesornovacuole
Starchgrainspresent StarchgrainsnotpresentDuetothecentralloca=onofthevacuole,thenucleusofthecellmaybelocatedattheedgeofthecell
Thenucleusisusuallylocatedcentrally
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PlantAnimal
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Plants and animals were constantly invaded by pathogens. However….. Is a couple of different strategy used for defend themselves ?
Mosaic disease Chicken pox
The mechanisms of plant and animal defense system show impressive structural and strategic similarity.
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Plant and Animal Defense
Pathogens
Physical barriers
PAMP-triggered immunity (PTI)
Effector-triggered immunity (ETI)
Plants
Hypersensitive Response
Animals
Vertebrates Invertebrates
Humoral response
B cells
Antigen Antibody
Cell-mediated response
Cytotoxic T cells
Infected cells
Innate immune system Plant immune system
Adaptive immune system
Plant
Phagocytes and Natural killer cells
Chondrichthyes Teleostei
Amphibia
Reptilia
Aves
Mammalia
Echinoderm
Prochordata
Agnatha
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PAMP-triggered immunity (PTI)
= Virus-induced gene silencing (VIGS)
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Virus induced gene silencing (VIGS) = PTI
Viral RNA
ウイルス複製酵素dsRNA (Replicative intermediate)
siRNA(21bp)siRNA(22bp)
Degradation of viral RNA
DCL2 DCL4
SDE3
RDR6
AGO
siRNA pathway
Viral RNA replicase
Phylogenetic analysis supports independent expansions of an ancient eukaryote Dicer protein in animals and plants.
Animal
Plant
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PAMP-triggered immunity (PTI)
= Virus-induced gene silencing (VIGS)
Effector-triggered immunity (ETI)
= Intracellular pattern recognition
receptors (PRRs)-mediated defense system
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Dr.ClaireThomas:OntheOriginsofPlantImmunity. Originsofahistoryofbeginnings.Blogs&Communi=es.JULY21,2009.
Plants and animals to resist infection show impressive structural and strategic similarity.
Plant cellsVertebrate and Invertebrate cells
Trans-membrane pattern-recognition receptor (PRR)
LRR
TIR
Intercellular PRR Variable NBS LRR
Trans-membrane PRR
Intercellular PRR
CC NBS LRR
TIR NBS LRR
LRR
Kinase
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Plant and Animal Defense
Pathogens
Physical barriers
PAMP-triggered immunity (PTI)
Effector-triggered immunity (ETI)
Plants
Hypersensitive Response
Animals
Vertebrates Invertebrates
Humoral response
B cells
Antigen Antibody
Cell-mediated response
Cytotoxic T cells
Infected cells
Innate immune system Plant immune system
Adaptive immune system
Plant
Phagocytes and Natural killer cells
Chondrichthyes Teleostei
Amphibia
Reptilia
Aves
Mammalia
Echinoderm
Prochordata
Agnatha
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1. Differences and similarities of immune system between plants and animals 2. Acute infection with plant viruses 3. “Virus latency and the impact on plants”
Contents
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Virus multiplication in single cell
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Virus particle
Uncoating
Viral RNA
Replicase
(-)RNA
Coat protein synthesis
Viral RNA
Virus assembly
Cell-to-cell movement protein
Plasmodesmata
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Virus induced gene silencing (VIGS) = PTI
ViralgenomeRNAViral genome RNA
Virus RNA replication
DICER
siRNA
RISC
RISC
RISC
Viral genome RNA
21-25nt small RNAs
Replicative intermediate dsRNA
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Virus induced gene silencing (VIGS) = PTI
ViralgenomeRNAViral genome RNA
Viral RNA replication
DICER
siRNA
RISC
RISC
Viral genome RNA
Silencing suppressor
Silencing suppressor
RISCSilencing suppressor
Replicative intermediate dsRNA
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Virus induced gene silencing (VIGS) = PTI
ViralgenomeRNAViral genome RNA
Viral RNA replication
DICER
siRNA
RISC
RISC
Viral genome RNA
Silencing suppressor
Silencing suppressor
RISCSilencing suppressor
miRNA gene
Pre-miRNA
miRNA
Target RNA: *Degradation *Translational regulation *DNA methylation
DICER
miRNA (21 base)
RISC
DICER
miRNA pathway
Replicative intermediate dsRNA
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Cell-to-cell Movement
Leaf tissue
Long-distance movement
Mosaic symptoms
Vasculer tissue
Inoculated leaf
Non-inoculated upper leaves
Single cell Virus
Susceptible response
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Specific cultivars of host plants carrying virus resistance gene can recognize viral proteins including silencing suppressor protein through intracellular immune receptor.
Trans-membrane PRR
CC NBS LRR
TIR NBS LRR
LRR
Kinase
Virus
Recognition
MAP kinase cascade
WRKY transcription factors
Defense-related gene expression
Intracellular immune receptor
Effector-triggered immunity (ETI)
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Virus mutants can escape from recognition by intracellular immune receptor thereby inactivating downstream signaling.
Evolutionary arms race
Trans-membrane PRR
Intracellular immune receptor
CC NBS LRR
TIR NBS LRR
LRR
Kinase
Virus mutants
Recognition
MAP kinase cascade
WRKY transcription factors
Defense-related gene expression
In the evolution of host plants, host plant creates new intracellular immune receptor gene, which can recognize this virus mutant.
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The most numerous R-gene class is represented by the gene family that encodes proteins containing a nucleotide-binding (NB) and leucine-rich repeats (LRRs) domains.
Marone et al. (2013) Int. J. Mol. Sci. 14: 7302-7326.
Nucleotide-binding site (NB)-leucine rich repeat (LRR) class R genes identified in different plant genomes.
CC/TIR domain
NB domain (ARC1) (ARC2)
LRR domain
Schematic representation of a typical NB-LRR protein
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This evolutionary arms race between virus and host plants is possibly explained by fitting it to “Red Queen Hypothesis”.
“Red Queen Hypothesis”
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3. “Virus latency and the impact on plants”
Contents
Agricultural ecosystem Natural ecosystem
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Wild plants seem be often latently infected with viruses, but impact of latent infection on host plants is not enough to be investigated.
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Arabidopsis halleri (Perennial plant)
Arabidopsis halleri and Arabidopsis thaliana
Arabidopsis thaliana(Annual plant)
https://www.ruhr-uni-bochum.de/pflaphy/Seiten_en/PG_Kraemer_e.html
After flowering, the stems fall down, and new seedlings develop from the axils. The seedlings can survive by rooting on soil.
Axils
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CCA
CCA
Cap
Cap
RNA1
RNA2
CCA Cap
RNA3
1a protein
2a protein
3a protein
2b protein
coat protein (CP)
Cucumber mosaic virus strain Ho : CMV(Ho)
! (+) single strand RNA genomes ! Host range: 1,200 species ! Strain: various isolates ! Transmission: aphid
2b gene
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CMV(Ho) systemically spread in plant, but any symptoms did not develop.
Arabidopsis thaliana inoculated with CMV(Ho)
CMV (Ho)
Mock
#1 #2 #3
#1 #2 #3
#1 #2 #3
#1 #2 #3
Immunological detection of virus coat protein by press blotting
CMV (Ho)
Mock
CMV(Ho)
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What is the determinant in 2b gene for latent infection with CMV(Ho)?
CCA
CCA
Cap
Cap
RNA1
RNA2
CCA Cap
RNA3 2b protein
77 106
2b protein
RNA silencing suppressor/siRNA-binding domain
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Cucumber mosaic virus strain Ho (CMV-Ho)
2b
CCA
CCA
Cap
Cap
RNA1
RNA2
CCA
Cap
RNA3
1a protein
2a protein
3a protein
2b protein
coat protein (CP)
CMV(Ho) genomic RNA
Change of gene expression
pattern
Phenotypes: Tolerance to environmental stresses etc.
DNA methylation
Working hypothesis regarding the impact of virus latent infection on the life of host plants
2b
2b
Change of DNA methylation
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This study was financially supported by grants for “Scientific Research on Innovative Areas” from the Ministry of Education, Culture, Science, Sports and Technology (MEXT) of Japan (Grant numbers: 16H06429, 16K21723 and 16H06435).
Acknowledgements