Trends in Plant Science
Volume 7, Issue 5, 1 May 2002, Pages 210-216
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Review
Priming in plant–pathogen interactions

https://doi.org/10.1016/S1360-1385(02)02244-6Get rights and content

Abstract

Plants can acquire enhanced resistance to pathogens after treatment with necrotizing attackers, nonpathogenic root-colonizing pseudomonads, salicylic acid, β-aminobutyric acid and many other natural or synthetic compounds. The induced resistance is often associated with an enhanced capacity to mobilize infection-induced cellular defence responses – a process called ‘priming’. Although the phenomenon has been known for years, most progress in our understanding of priming has been made only recently. These studies show that priming often depends on the induced disease resistance key regulator NPR1 (also known as NIM1 or SAI1) and that priming has a major effect on the regulation of cellular plant defence responses.

Section snippets

Priming and systemic acquired resistance

The systemic resistance response activated upon infection of plants with necrotizing pathogens is called systemic-acquired resistance (SAR) 1., 2., but SAR can also be induced by exogenous application of salicylic acid or its functional analogues 2,6-dichloroisonicotinic acid (ina) and benzothiadiazole (bth) 1., 2., 17.. Establishment of SAR requires an endogenous increase in salicylic acid levels 1., 2., 17. and its onset is associated with the expression of SAR genes [1], some of which encode

Priming and rhizobacteria

Priming of defence responses is not solely confined to the SAR response. Priming of defence responses has also been demonstrated in rhizobacterium-mediated induced systemic resistance (ISR). Rhizobacterium-mediated ISR is a plant-mediated, broad-spectrum resistance response that is activated by selected strains of saprophytic rhizosphere bacteria [3]. The first evidence that potentiation of plant defence responses is involved in ISR came from experiments with carnation (Dianthus caryophyllus).

Priming Arabidopsis with BABA

The non-protein amino acid BABA has been known for years to be an effective inducer of resistance in various crops [4]. However, it became apparent only recently that this substance exerts its effect on the defence capability of plants via priming 9., 55.. In Arabidopsis, BABA pretreatment leads to a more rapid and stronger deposition of callose-containing papillae at the site of infection by Peronospora parasitica [9]. When BABA-pretreated Arabidopsis plants are challenged with a virulent

Priming against abiotic stresses

As described above for the potentiated response of systemic resistant Arabidopsis to stimulation by wounding or the infiltration of water into the leaves, plants are also known to display priming-like reactions to abiotic stresses. Pretreatment with cold can lead to acclimation, which manifests itself in the ability of a plant to survive much lower temperatures than without this pretreatment [59]. In Arabidopsis, similar results can be obtained upon pretreatment with BABA before subjecting the

Cell priming in animals and humans

The priming for potentiated induction of pathogen defence responses in plants has phenotypic similarity to the administration of defence responses in animals and humans. For example, in adult female locusts, application of a subclinical dose of the active juvenile hormone analogue methoprene accelerates (potentiates) the appearance of the egg-yolk protein vitellogenin induced by normal doses of juvenile hormone [62]. Furthermore, pretreatment with granulocyte–macrophage colony-stimulating

Conclusions

Induced disease resistance of plants is a widely observed phenomenon and priming for potentiated induction of defence responses has emerged as being an important part. The mode of action of priming and the resulting potentiation of cellular defence responses, rather than the direct upregulation of defence signalling cascades, might prove to be of enormous advantage in terms of energy costs for the plant, because the defence responses are only expressed when they are really needed – upon

Acknowledgements

We apologize to all our colleagues whose work could not be reviewed here because of space limitations. Part of the work presented in this review was supported by the Swiss National Foundation (grant 31–064024 to B.M-M.) and by BASF and Syngenta (grants to U.C.). We thank Felix Mauch (University of Fribourg, Switzerland) for critically reading the manuscript.

Glossary

β-Aminobutyric acid (BABA):
Non-protein amino acid that potentiates plant responses and confers resistance to biotic and abiotic stresses.
Avirulent:
A pathogen strain that carries an avirulence (Avr) gene and cannot multiply in a resistant host plant cultivar expressing a complementary resistance gene.
Benzothiadiazole (BTH):
Synthetic compound inducing SAR in various plants.
Callose:
Plant 1,3-β-glucan contributing to cell wall strengthening beneath fungal penetration sites in the form of papillae.

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