Bacterium-induced basal resistance inhibits viral infection in tobacco plants László ZSIROS 1,2,...
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Transcript of Bacterium-induced basal resistance inhibits viral infection in tobacco plants László ZSIROS 1,2,...
Bacterium-induced basal resistance inhibits viral infection
in tobacco plants
László ZSIROS1,2, Ágnes SZATMÁRI1,
László PALKOVICS2, Zoltán KLEMENT1 Zoltán BOZSÓ1
1Plant Protection Institute of the HAS2 Corvinus University of Budapest Dept. of Plant Pathology
Main types of resistance in plants
Preformed Microorganism-induced
Hypersensitive response(HR)
Basal resistance(BR)
Early basal resistance(EBR)
Late basal resistance (LBR)
Comparison of basal and hypersensitive defense
Type of resistance Hypersensitive Basal
Plant-bacterium interaction
Specific Non-specific
Inducer bacterium Metabolically active pathogen
Pathogen, saprotroph, heat killed, etc.
Symptom Cell necrosis Symptomless
(detection with superinfection)
Induction of basal resistance (BR) and hypersensitive response (HR)
Plant cell
Basal resistance
Flagellin, LPSAvr proteins
Hypersensitive response
Intercellular space
Tobacco mosaic virus (TMV)
• Resistance in tobacco• HR – 78 hours• N gene
• Plant-TMV interaction• incompatible (HR)• compatible (mosaic leaves)
Changes at cell level during basal resistance (BR)
• change in pH level
• cell wall fortification
• papilla formation
• active oxygen forms (eg. hydrogen peroxide)
• bacterium envelopment
Aims of research
• Does a bacterial infection impede the symptoms/HR of a viral superinfection?
• Is symptom/HR inhibition attached to bated virus replication?
• How do some defense-related genes change in their transcription activity?
Materials and methods
• Plants– N. tabacum L. ‘Samsun’ nn (compatible)– N. tabacum L. ‘Xanthi’ NN (incompatible)
• Bacterial inoculation– Pseudomonas syringae pv. syringae hrcC mutant
• Viral inoculation– TMV
• Virus quantity and gene activity assay– Real-Time PCR
Inoculation method to assay early basal resistance (EBR)
Bacterial inoculationWater infiltration (mock) Viral inoculation
6 hours
TMV
HR-inhibition assay(‘Xanthi’ NN plant, incompatible tobacco-TMV interaction)
Bacterium (hrcC) + TMV
Water + TMV
Positive control (TMV only)
HR-inhibition assay(‘Xanthi’ NN plant, incombatible tobacco – TMV interaction)
Plant Pre-treatment Number of lesions
Size of lesions
Positive control
(TMV only)
- 228 2-3 mm
Early basal resistance
Water 188 2-3 mm
Bacterium 67 1 mm
Average results of repeated treatments
Inhibition of virus replication(‘Xanthi’ NN plant, incombatible tobacco – TMV interaction)
Representative results of repeated treatments
hrcC = Pseudomonas syringae pv. syringae hrcC mutáns
0.01
0.1
1
10
100
1000
0 1 2 3 4
days post TMV inoculation
Vir
us
qu
anti
ty a
s co
mp
ared
to
to
bac
co
acti
n e
xpre
ssio
n l
evel
TMV
Water + TMV
hrcC + TMV
Defense-related genes (‘Xanthi’ NN plant, incompatible tobacco – TMV interaction)
• Epoxide hydrolase – epoxide neutralization
• Ortho-methyl trasferase – cell wall synthesis
• Superoxide dismutase – superoxide degradation
Defense-related genes 1 (‘Xanthi’ NN plant, incompatible tobacco – TMV interaction)
Epoxide hydrolase
0
1
2
3
4
5
6
7
8
9
0 1 2 3 4
days post TMV inoculation
Gen
e ex
pre
ssio
n a
s co
mp
ared
to
u
ntr
eate
d c
on
tro
l
TMV
Water + TMV
hrcC + TMV
Representative results of repeated treatments
hrcC = Pseudomonas syringae pv. syringae hrcC mutant
Defense-related genes 2 (‘Xanthi’ NN plant, incompatible tobacco – TMV interaction)
Representative results of repeated treatments
hrcC = Pseudomonas syringae pv. syringae hrcC mutant
Ortho-methyl transferase
0
5
10
15
20
25
30
0 1 2 3 4
days post TMV inoculation
Gen
e ex
pre
ssio
n a
s co
mp
ared
to
u
ntr
eate
d c
on
tro
l
TMV
Water + TMV
hrcC + TMV
Defense-related genes 3 (‘Xanthi’ NN plant, incompatible tobacco – TMV interaction)
Representative results of repeated treatments
hrcC = Pseudomonas syringae pv. syringae hrcC mutant
Superoxide dismutase
0
1
2
3
4
5
6
7
8
0 1 2 3 4
days post TMV inoculation
Gen
e ex
pre
ssio
n a
s co
mp
ared
to
u
ntr
eate
d c
on
tro
l
TMV
Water + TMV
hrcC + TMV
Symptom inhibition of EBR(‘Samsun’ nn plant, compatible tobacco – TMV interaction)
Water + TMV Bacterium + TMV TMV
Inhibition of virus replication(‘Samsun’ nn plant, compatible tobacco – TMV interaction)
Representative results of repeated treatments
hrcC = Pseudomonas syringae pv. syringae hrcC mutant
0.001
0.01
0.1
1
10
100
1000
10000
100000
1000000
0 1 2 3 4
days post TMV inoculation
Vir
us
qu
anti
ty a
s co
mp
ared
to
to
bac
co
acti
n e
xpre
ssio
n l
evel
TMV
Water + TMV
hrcC + TMV
Summary
• Related to EBR, there was inhibition observed in
– mosaic leaf symptom development;
– virus-induced HR development;
– the rate of virus replication;
– change in activity of some defense-related genes
Conclusions
• Possible reasons for HR or mosaic symptom inhibition during basal resistance:
– blocking of virus translocation in plant
– inhibition of virus replication (RNA silencing? priming?)
– non-specific defense
– hydrogen peroxide symptoms