scholarly journals Accumulation of Salicylic Acid and 4-Hydroxybenzoic Acid in Phloem Fluids of Cucumber during Systemic Acquired Resistance Is Preceded by a Transient Increase in Phenylalanine Ammonia-Lyase Activity in Petioles and Stems

1998 ◽  
Vol 116 (1) ◽  
pp. 231-238 ◽  
Author(s):  
Jennifer Smith-Becker ◽  
Eric Marois ◽  
Elisabeth J. Huguet ◽  
Sharon L. Midland ◽  
James J. Sims ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Phenylalanine Ammonia Lyase ◽  
Systemic Acquired Resistance ◽  
Acquired Resistance ◽  
Transient Increase ◽  
Hydroxybenzoic Acid ◽  
Lyase Activity ◽  
Phenylalanine Ammonia Lyase Activity

scholarly journals Nanogram Amounts of Salicylic Acid Produced by the Rhizobacterium Pseudomonas aeruginosa 7NSK2 Activate the Systemic Acquired Resistance Pathway in Bean

1999 ◽  
Vol 12 (5) ◽  
pp. 450-458 ◽  
Author(s):  
Geert De Meyer ◽  
Kristof Capieau ◽  
Kris Audenaert ◽  
Antony Buchala ◽  
Jean-Pierre Métraux ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Salicylic Acid ◽  
Induced Resistance ◽  
Phenylalanine Ammonia Lyase ◽  
Systemic Acquired Resistance ◽  
Acquired Resistance ◽  
Systemic Resistance ◽  
Resistance Pathway ◽  
Lyase Activity ◽  
Phenylalanine Ammonia Lyase Activity

Root colonization by specific nonpathogenic bacteria can induce a systemic resistance in plants to pathogen infections. In bean, this kind of systemic resistance can be induced by the rhizobacterium Pseudomonas aeruginosa 7NSK2 and depends on the production of salicylic acid by this strain. In a model with plants grown in perlite we demonstrated that Pseudomonas aeruginosa 7NSK2-induced resistance is equivalent to the inclusion of 1 nM salicylic acid in the nutrient solution and used the latter treatment to analyze the molecular basis of this phenomenon. Hydroponic feeding of 1 nM salicylic acid solutions induced phenylalanine ammonia-lyase activity in roots and increased free salicylic acid levels in leaves. Because pathogen-induced systemic acquired resistance involves similar changes it was concluded that 7NSK2-induced resistance is mediated by the systemic acquired resistance pathway. This conclusion was validated by analysis of phenylalanine ammonia-lyase activity in roots and of salicylic acid levels in leaves of soil-grown plants treated with Pseudomonas aeruginosa. The induction of systemic acquired resistance by nanogram amounts of salicylic acid is discussed with respect to long-distance signaling in systemic acquired resistance.

scholarly journals Spatial and temporal regulation of biosynthesis of the plant immune signal salicylic acid

2015 ◽  
Vol 112 (30) ◽  
pp. 9166-9173 ◽  
Author(s):  
Xiao-yu Zheng ◽  
Mian Zhou ◽  
Heejin Yoo ◽  
Jose L. Pruneda-Paz ◽  
Natalie Weaver Spivey ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Systemic Acquired Resistance ◽  
Acquired Resistance ◽  
Signal Transduction Pathway ◽  
Temporal Regulation ◽  
Calmodulin Binding ◽  
Regulation Of Biosynthesis ◽  
Pathogen Entry ◽  
Transcription Activators ◽  
Transcriptional Induction

The plant hormone salicylic acid (SA) is essential for local defense and systemic acquired resistance (SAR). When plants, such as Arabidopsis, are challenged by different pathogens, an increase in SA biosynthesis generally occurs through transcriptional induction of the key synthetic enzyme isochorismate synthase 1 (ICS1). However, the regulatory mechanism for this induction is poorly understood. Using a yeast one-hybrid screen, we identified two transcription factors (TFs), NTM1-LIKE 9 (NTL9) and CCA1 HIKING EXPEDITION (CHE), as activators of ICS1 during specific immune responses. NTL9 is essential for inducing ICS1 and two other SA synthesis-related genes, PHYTOALEXIN-DEFICIENT 4 (PAD4) and ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1), in guard cells that form stomata. Stomata can quickly close upon challenge to block pathogen entry. This stomatal immunity requires ICS1 and the SA signaling pathway. In the ntl9 mutant, this response is defective and can be rescued by exogenous application of SA, indicating that NTL9-mediated SA synthesis is essential for stomatal immunity. CHE, the second identified TF, is a central circadian clock oscillator and is required not only for the daily oscillation in SA levels but also for the pathogen-induced SA synthesis in systemic tissues during SAR. CHE may also regulate ICS1 through the known transcription activators CALMODULIN BINDING PROTEIN 60g (CBP60g) and SYSTEMIC ACQUIRED RESISTANCE DEFICIENT 1 (SARD1) because induction of these TF genes is compromised in the che-2 mutant. Our study shows that SA biosynthesis is regulated by multiple TFs in a spatial and temporal manner and therefore fills a gap in the signal transduction pathway between pathogen recognition and SA production.

scholarly journals Systemic Acquired Resistance in Canola Is Linked with Pathogenesis-Related Gene Expression and Requires Salicylic Acid

2007 ◽  
Vol 97 (7) ◽  
pp. 794-802 ◽  
Author(s):  
Shobha D. Potlakayala ◽  
Darwin W. Reed ◽  
Patrick S. Covello ◽  
Pierre R. Fobert
Keyword(s):  
Salicylic Acid ◽  
Pseudomonas Syringae ◽  
Systemic Acquired Resistance ◽  
Induced Defense ◽  
Acquired Resistance ◽  
Microbial Pathogens ◽  
Broad Host Range ◽  
Avirulent Strain ◽  
Enhanced Resistance ◽  
Pathogenesis Related

Systemic acquired resistance (SAR) is an induced defense response that confers long-lasting protection against a broad range of microbial pathogens. Here we show that treatment of Brassica napus plants with the SAR-inducing chemical benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) significantly enhanced resistance against virulent strains of the bacterial pathogen Pseudomonas syringae pv. maculicola and the fungal pathogen Leptosphaeria maculans. Localized preinoculation of plants with an avirulent strain of P. syringae pv. maculicola also enhanced resistance to these pathogens but was not as effective as BTH treatment. Single applications of either SAR-inducing pretreatment were effective against P. syringae pv. maculicola, even when given more than 3 weeks prior to the secondary challenge. The pretreatments also led to the accumulation of pathogenesis-related (PR) genes, including BnPR-1 and BnPR-2, with higher levels of transcripts observed in the BTH-treatment material. B. napus plants expressing a bacterial salicylate hydroxylase transgene (NahG) that metabolizes salicylic acid to catechol were substantially compromised in SAR and accumulated reduced levels of PR gene transcripts when compared with untransformed controls. Thus, SAR in B. napus displays many of the hallmarks of classical SAR including long lasting and broad host range resistance, association with PR gene activation, and a requirement for salicylic acid.

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