Mechanism of non host resistance against bacterial pathogens. Presented by Rahul Bakade

1. Mechanism of non-host resistance
against bacterial pathogen
• Rahul Bakade
Rahul Bakade 1

2. Flow of presentation
• Introduction
• Plant pathogenic bacterial interaction with plant
• Non-host Defense strategies
• Types of non host resistance
• Mechanisms of non-host resistance
• Case studies
• Conclusion
2Rahul Bakade

3. Fungus
Viruses
Bacteria
Nematodes
H.R.
PR genes
ROS
RESISTANCE
Host specific Non-host specific
Non-host pathogen
3
Introduction
Rahul Bakade

4. 4
Tomato
pathogen
Potato
pathogen
Maize
pathogen
I am not
your host
You go away
You can come
I am resistant
to most of the
pathogens
More durable
Non-host resistance
Wide range
NHR, still poorly understood
To understand answer this
• What are component?
• Are there different types?
• Are there similarities with host resistance?
Multi-tiered
Rahul Bakade

5. Plant pathogenic bacterial
interaction with plant
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6. 6
Entry
wounds
How bacteria enters and cause disease ?
Rahul Bakade

7. Bacteria multiply in
apoplastic region
How bacteria enters and cause disease ?
PHYTOTOXIN EXTRACELLULAR POLYSACCHARIDES PHYTOHORMONES
Access nutrients in the apoplast
T3SS
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8. Non-host Defense strategies
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9. Three step process of non-host resistance
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Muthappa et al., 2013
Resistance
First line of defence
second line of defence
Third line of defence
Rahul Bakade

10. Relationship between host-specific and non-
host resistance
Host-specific resistance Non-host resistance
pathogen
Pathogen gene Avr Xa21
Signal
Z
LRRRecognition Multiple receptors in plant
Xa21 Response genes
Signal transduction
Disease resistance
Activation of
disease resistance
response genes
Xoo P.s. pv. tabaci
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In Rice Arabidopsis
Rahul Bakade

11. 11
Type of non-host resistance
Rahul Bakade

12. Mechanism of non-host resistance
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13. Mechanism of non-host resistance
1. Nutrients limitations
2. Reactive Oxygen Species Signaling
3. Hypersensitive Response
4. PAMP-Triggered Immunity in Non-host Resistance
5. Effector-Triggered Immunity in Non-host Resistance
13Rahul Bakade

14. Nutrients limitations
 It is sequestered in the cell wall region (not accessible to
bacteria )
 Restricting the availability of nutrients
14(Wang et al., 2012)
Apoplastic region
• Pathogens depend on the
apoplast for nutrients
• Constantly exchanged of
nutrients between the
cytosol and the apoplast
Rahul Bakade

15. Reactive Oxygen Species Signaling
• Accumulation of ROS in infected plant
• Acts as signalling to activate defence cascade
• Eg.Photorespiratory ROS production by glycolate
oxidase (GOX) has been shown to play a direct role in
nonhost resistance
15(Rojas et al., 2012)Rahul Bakade

16. Hypersensitive Response
• Defense responses induced usually culminate in HR
cell death
– polyamines are important sources of ROS that provoke HR
in N. benthamiana inoculated with the non-host pathogen
P. cichorii. (Yoda et al., 2012)
– proline dehydrogenase (ProDH1 and ProDH2) exhibited HR
and provide resistance against the nonhost pathogen P.
syringae pv. tomato T1
(Muthappa et al., 2013)
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17. 17
Induces
Callose deposition
ROS
Phenolic compounds
PAMP-Triggered Immunity in Nonhost
Resistance
Rahul Bakade

18. 18
Effector-Triggered Immunity in Nonhost
Resistance
Eg. Arabidopsis, triggers ETI by recognizing
hopAS1 (T3SS effector), from P. syringae pv.
tomato T1
(Sohn et al., 2012)
Rahul Bakade

19. CASE STUDY: 1
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20. objective:
– identification and characterization of
genes involved in non-host resistance,
by the VIGS approach by screening a
normalized N.benthamiana cDNA
library.
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21. NbRPL12 and NbRPL19 Silenced Plants Show a
Delay in Non-host Pathogen Induced HR
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Silencing of NbRPL12 and NbRPL19
genes in N. benthamiana delayed
development of HR in non-host
pathogen (P. syringea pv. tomato 1)
inoculated leaves.
Rahul Bakade

22. NbRPL 12 and NbRPL 19 Silenced Plants Have
Increased Non-host Pathogen Multiplication
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23. NbRPL 12 and NbRPL 19 Silenced Plants Increased
Non-host Pathogen Multiplication by dip inoculated
23
Enhanced accumulation of non-host pathogen P.syringae pv. tomato T1 on dip
inoculated NbRPL 12 and NbRPL 19 gene silenced N. benthamiana leaves.
Rahul Bakade

24. NbRPL 12 and NbRPL 19 Silenced Plants Increased
Non-host Pathogen Multiplication by vacuum
infiltration
Figure : 4 24
Disease symptoms in the NbRPL12 and NbRPL19 gene silenced N. benthamiana by
vacuum infiltration
Rahul Bakade

25. Expression level of NbRPL12 and NbRPL19
25
Transcript expression
pattern of NbRPL12 and
NbRPL19 in wild-type N.
benthamiana leaves
challenged with host or
non-host
Rahul Bakade

26. Multiplication of non-host pathogen and host
pathogen on Atrpl12 and Atrpl19 mutants
of Arabidopsis.
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27. CASE STUDIES: 2
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28. 28
Objective :
Identification of noval genes responsible for stomatal
aperture regulation and thus in plant innate immunity and
drought tolerance.
Rahul Bakade

29. Silencing of the 4D7-2 cDNA Clone in N. benthamiana
Enhances Multiplication of Host and Non-host
Pathogens
29Syringe infiltration
Vacuum infiltration
silencing of 4D7-2 compromises defense responses in N.
benthamiana plants
Rahul Bakade

30. AtGCN4 Plays an Active Role in Plant Immunity against
Bacterial Pathogens in Arabidopsis
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31. AtGCN4 RNAi Plants Compromise Nonhost Disease
Resistance, and Overexpression Plants Show Tolerance
to Host Pathogen.
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32. AtGCN4 RNAi Plants Compromise Nonhost Disease
Resistance, and Overexpression Plants Show Tolerance
to Host Pathogen.
32
AtGCN4 has a dual role in plant defense, one through stomata-mediated
immunity and the other through apoplastic defense
Rahul Bakade

33. CASE STUDIES: 3
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34. 34
Objective:
Screening of genes required for non-host resistance to
Xanthomonas oryzae pv. oryzae , based on functional
analysis by virus-induced gene silencing (VIGS) and HR
detection assays.
Rahul Bakade

35. Necrosis symptoms in Nicotiana benthamiana leaves
infiltrated with Xanthomonas oryzae pv. oryzae (Xoo) and a
hrcU mutant.
hrcU is required
for YN-1
elicitation of
hypersensitive
necrosis
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36. accumulation of H2O2in Xoo-infiltrated area prior to
formation of hypersensitive necrosis (DAB)
H2O2 accumulation occurred
before hypersensitive necrosis
was visible.
36
At tissue levelΔhrcU YN-1 At tissue levelΔhrcU YN-1
Rahul Bakade

37. Upregulation of HR- and defense-related genes
in Xoo-infiltrated leaves
These results
support the
hypothesis that
the necrosis
observed in Xoo
infiltrated leaves
is a type of HR.
37
Defence regulatory genes
HR marker genes
Rahul Bakade

38. Effect of silencing (VIGS) of seven ACE genes on Xoo
induced HR in N. benthamian
ACE genes for
silencing
Average percentage
HR+ leaves ± SE
CK 93.3
ACE 35 29.2
ACE 43 28.6
ACE 80 33.7
ACE 95 7.9
ACE 112 31.0
ACE 117 27.9
ACE 175 19.8
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Disease score
Identify Genes Required for the HR in the Xoo N. benthamiana InteractionRahul Bakade

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THANK YOU
Rahul Bakade