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Tomato roots exhibit in vivo glutamate dehydrogenase aminating capacity in response to excess ammonium supply

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Title Tomato roots exhibit in vivo glutamate dehydrogenase aminating capacity in response to excess ammonium supply
 
Creator Vega-Mas, I.
Rossi, M.T.
Gupta, Kapuganti Jagadis
González-Murua, C.
Ratcliffe, R.G.
Estavillo, J.M.
González-Moro, M.B.
 
Subject Asparagine synthetase
Glutamate dehydrogenase
Ammonium nutrition
Methionine sulphoximine
Azaserine
Isotope labelling
 
Description Accepted date: 27 March 2019
In higher plants ammonium (NH4+) assimilation occurs mainly through the glutamine synthetase/glutamate synthase (GS/GOGAT) pathway. Nevertheless, when plants are exposed to stress conditions, such as excess of ammonium, the contribution of alternative routes of ammonium assimilation such as glutamate dehydrogenase (GDH) and asparagine synthetase (AS) activities might serve as detoxification mechanisms. In this work, the in vivo functions of these pathways were studied after supplying an excess of ammonium to tomato (Solanum lycopersicum L. cv. Agora Hybrid F1) roots previously adapted to grow under either nitrate or ammonium nutrition. The short-term incorporation of labelled ammonium (15NH4+) into the main amino acids was determined by GC–MS in the presence or absence of methionine sulphoximine (MSX) and azaserine (AZA), inhibitors of GS and GOGAT activities, respectively. Tomato roots were able to respond rapidly to excess ammonium by enhancing ammonium assimilation regardless of the previous nutritional regime to which the plant was adapted to grow. The assimilation of 15NH4+ could take place through pathways other than GS/GOGAT, since the inhibition of GS and GOGAT did not completely impede the incorporation of the labelled nitrogen into major amino acids. The in vivo formation of Asn by AS was shown to be exclusively Gln-dependent since the root was unable to incorporate 15NH4+ directly into Asn. On the other hand, an in vivo aminating capacity was revealed for GDH, since newly labelled Glu synthesis occurred even when GS and/or GOGAT activities were inhibited. The aminating GDH activity in tomato roots responded to an excess ammonium supply independently of the previous nutritional regime to which the plant had been subjected.
Authors are grateful to the Basque Government [Grant ref.: BFI-2010-365 to IVM and IT932-16] and the Spanish Ministry of Economy and Competitiveness [AGL2015-64582-C3-2-R and AGL2014-54413-R, MINECO/FEDER, UE] for providing financial support to carry out this work.
 
Date 2019-09-25T09:23:37Z
2019-09-25T09:23:37Z
2019
 
Type Article
 
Identifier Journal of Plant Physiology, 239: 83-91
0176-1617
http://223.31.159.10:8080/jspui/handle/123456789/989
https://www.sciencedirect.com/science/article/pii/S0176161718306515
https://doi.org/10.1016/j.jplph.2019.03.009
 
Language en_US
 
Format application/pdf
 
Publisher Elsevier B.V.