Induced Systemic Resistance
(ISR)
- Plant responses to plant growth promoting rhizobacteria
- Herbivore induced resistance
Biologically induced systemic resistance
Pieterse et al. (2014) Annu. Rev. Phytopathol. 52:347-75
Conrath. 2011. Trends Plant Sci. 16:524-531
Root colonization by beneficial soil bacteria
Pieterse et al. (2014) Annu. Rev. Phytopathol. 52:347-75
Plant growth-promoting effects of P. fluorescens WCS417r
Pieterse et al. (2014) Annu. Rev. Phytopathol. 52:347-75
Systemic protection against Cucumber mosaic virus
Nonbacterized
Bacillus pumulis strain SE34
Kloepper. 2004. Phytopathology. 94:1259-1266
P. fluorescens WCS417r and iron deficiency induce MYB72
Pieterse et al. (2014) Annu. Rev. Phytopathol. 52:347-75
Properties of PGPR
- Stimulate growth
• N fixation
• Increase solubility of limiting nutrients (siderophores)
• Stimulate nutrient delivery and uptake
• Production of phytohormones
• Modulation of plant development (e.g. reduce ethylene
enhances root growth)
- Plant-mediated disease suppression
• Non-pathogens antagonize pathogens (competition,
antibiotics, lytic enzymes)
• Activating plant to better defend itself (ISR)
• Induced resistance observed on spatially separated
parts of same plant
The nature of systemically induced resistance in plants
(A) Characteristics of induced systemic resistance
• The defensive capacity of the plant is enhanced through microbial stimulation or
similar stresses
• The enhanced defensive capacity is expressed systemically throughout the
plant
• Induced systemic resistance is active against fungi, bacteria, viruses and,
sometimes, nematodes and insects
• Once induced, systemic resistance is maintained for prolonged periods
(B) Mechanisms of induced systemic resistance
• Developmental, escape: linked to growth promotion
• Physiological, tolerance: reduced symptom expression
• Environmental: associated with microbial antagonism in the rhizosphere;
altered plant-insect interactions
• Biochemical, resistance: induction of cell wall reinforcement,
• Induction of phytoalexins
• Induction of pathogenesis-related proteins
• ‘Priming’ of defence responses (resistance)
From Van Loon (2007) Eur. J. Plant Pathol. 119:243-254
ISR potentiates plant defense responses
Fusarium wilt of carnation and radish
Biocontrol by P. fluorescens WCS358
• Iron competition important: sid- mutant not effective
Biocontrol by P. fluorescens WCS417
• Twice as effective
• Sid-mutant still 100% effective
• Worked when WCS417 and fusarium were spatially separated on the
plant*
• WCS417 did not trigger phytoalexin accumulation*
• WCS417 treated plants produced more phytoalexin in response to
Fusarium*
Root rot in bean
Accelerated and potentiated papilla formation
*Van Peer et al (1991) Phytopathol 81:728-734
Plant-mediated*, broad-spectrum resistance response that is
activated by selected strains of saprophytic rhizosphere
bacteria. Many are PGPR. PGPR colonization non-specific;
ability to induce SR has some specificity. * Inducing bacteria and
pathogen can be spatially isolated
Summary of ISR molecular properties
•
•
•
•
•
ISR potentiates plant defense responses
ISR is SA-independent
ISR is independent of PR gene activation
ISR requires JA and C2H4 response pathways
ISR not associated with JA- and C2H4-responsive gene
activation
• ISR primes plant for enhanced C2H4 production?
• Summary: compare and contrast ISR and SAR
• Not covered in class:
1) bacterial determinants of ISR
2) field application of ISR
Changes in gene expression in bacterized plants
From Van Loon (2007) Eur. J. Plant Pathol. 119:243-254
Specificity in ISR induction by Pseudomonas spp. strains
Root colonization is similar in all cases
From Van Loon (2007) Eur. J. Plant Pathol. 119:243-254
Model system – Arabidopsis/Pseudomonas fluorescens WCS417r
For
Control
WCS417r
Ps
–
ISR is SA-independent
W
Fusarium
–
W
P. syringae
Pieterse et al. (1996) Plant Cell 8, 1225-1237
ISR is independent of PR gene activation
Pieterse et al. (1996) Plant Cell 8, 1225-1237
*just prior to challenge inoc
ISR requires JA and C2H4 response pathways
Pieterse et al. (1998) Plant Cell 10, 1571-158
ISR requires JA and C2H4 response pathways
in that order
Pieterse et al. (1998) Plant Cell 10, 1571-158
Pieterse et al. (1998) Plant Cell 10, 1571-158
ISR not associated with JA- and C2H4-responsive gene
activation
But expression of this (and
not others) is potentiated in
plants undergoing ISR
Van Wees et al. (1999) Plant Mol Biol
41:537-549
So ISR is associated with
potentiation of a specific
set of JA-responsive
genes?
Also, increased sensitivity
rather than increased
production of JA and
C2H4
(see also Pieterse et al. 2000 Physiol.
Mol. Plant Pathol. 57:123-134)
Pieterse et al. (1998) Plant Cell 10, 1571-158
ISR primes plant for enhanced C2H4 production?
ISR plants do not show increased levels of C2H4, or JA,
but
ISR activated plants convert more ACC to C2H4
MYC2 transcription factor involved in priming induced systemic resistance
Pozo. 2008. New Phytol. 180:511-523
Herbivore induce resistance
Differential JA responses in Col-0 and jin1 plants in local and systemic leaves
Vos. 2013. Front. Plant Sci. 4:539
Production of JA, JA-Ile, OPDA, and ABA in local and systemic Col-0 leaves
Vos. 2013. Front. Plant Sci. 4:539
Effects of P. rapae and ABA on MYC and VSP1 expression
Vos. 2013. Front. Plant Sci. 4:539
Effect of herbivory on P. rapae performance in Col-0, aba2-1, and coi1-1 plants
Vos. 2013. Front. Plant Sci. 4:539
Model for herbivore induced resistance in Arabidopsis
Vos. 2013. Front. Plant Sci. 4:539
Comparison of SAR, HIR, and ISR mechanisms
Pieterse et al. (2014) Annu. Rev. Phytopathol. 52:347-75
Discussion
1) why is it important to study ISR?
2) do differences between ISR, HIR, SAR matter?
3) selective advantage to the plant and practical
significance?
4) what role does root microbiome play in immunity
5) how might ISR be triggered?