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Moving nitrogen to the centre of plant defence against pathogens

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Title Moving nitrogen to the centre of plant defence against pathogens
 
Creator Mur, Luis A.J.
Simpson, Catherine
Kumari, Aprajita
Gupta, Alok Kumar
Gupta, Kapuganti Jagadis
 
Subject Nitric oxide
nitrate
ammonium
Pseudomonas
polyamines
nitrate reductase
plant defence
 
Description Accepted date: June 8, 2016
Background Plants require nitrogen (N) for growth, development and defence against abiotic and biotic stresses. The extensive use of artificial N fertilizers has played an important role in the Green Revolution. N assimilation can involve a reductase series (NO–3→ NO–2 → NH+4) followed by transamination to form amino acids. Given its widespread use, the agricultural impact of N nutrition on disease development has been extensively examined. Scope: When a pathogen first comes into contact with a host, it is usually nutrient starved such that rapid assimilation of host nutrients is essential for successful pathogenesis. Equally, the host may reallocate its nutrients to defence responses or away from the site of attempted infection. Exogenous application of N fertilizer can, therefore, shift the balance in favour of the host or pathogen. In line with this, increasing N has been reported either to increase or to decrease plant resistance to pathogens, which reflects differences in the infection strategies of discrete pathogens. Beyond considering only N content, the use of NO-3 or NH+4 fertilizers affects the outcome of plant–pathogen interactions. NO-3 feeding augments hypersensitive response- (HR) mediated resistance, while ammonium nutrition can compromise defence. Metabolically, NO–3 enhances production of polyamines such as spermine and spermidine, which are established defence signals, with NH+4 nutrition leading to increased γ-aminobutyric acid (GABA) levels which may be a nutrient source for the pathogen. Within the defensive N economy, the roles of nitric oxide must also be considered. This is mostly generated from NO–2 by nitrate reductase and is elicited by both pathogen-associated microbial patterns and gene-for-gene-mediated defences. Nitric oxide (NO) production and associated defences are therefore NO-3 dependent and are compromised by NH+4.
Conclusion:This review demonstrates how N content and form plays an essential role in defensive primary and secondary metabolism and NO-mediated events.
This work is currently being supported by a DST-UKIERI thematic partnership award to K.J.G. and L.A.J.M. K.J.G. is currently supported by a Ramalingaswami Fellowship and Innovate Young Biotechnology Award (IYBA) by the Department of Biotechnology, Government of India. We thank Aakanksha Wany for critical reading of the manuscript, and also thank the handling editor for providing valuable suggestions for improvement of this manuscript.
 
Date 2016-09-14T11:31:33Z
2016-09-14T11:31:33Z
2017
 
Type Article
 
Identifier Ann. Bot., 119(5): 703-709
1095-8290
http://172.16.0.77:8080/jspui/handle/123456789/680
http://aob.oxfordjournals.org/content/early/2016/09/02/aob.mcw179.full
10.1093/aob/mcw179
 
Language en_US
 
Publisher Oxford University Press