The interaction between rhizobia and their legume host plants conduces to the formation of specialized root organs called nodules where rhizobia differentiate into bacteroids which fix atmospheric nitrogen to the benefit of the plant. This beneficial symbiosis is of importance in the context of sustainable agriculture as legumes do not require the addition of nitrogen fertilizer to grow. Interestingly, nitric oxide (NO) has been detected at various steps of the rhizobium–legume symbiosis where it has been shown to play multifaceted roles. Both bacterial and plant partners are involved in NO synthesis in nodules. To better understand the role of NO, and in particular the role of bacterial NO, at all steps of rhizobia–legumes interaction, the enzymatic sources of NO have to be elucidated. In this review, we discuss different enzymatic reactions by which rhizobia may potentially produce NO. We argue that there is most probably no NO synthase activity in rhizobia, and that instead the reductase nirK, which is part of the denitrification pathway, is the main bacterial source of NO. The nitrate assimilation pathway might contribute to NO production but only when denitrification is active. The different approaches to measure NO in rhizobia are also addressed.
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February 2021
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On the implications of the copper co-factor in lytic polysaccharide monooxygenase. A brief overview of structure, oxygen activation and application as bioindustrial process tools for decomposition of lignocellulose. Further information can be found in the review by Ipsen and colleagues (pages 531–540). Image provided by Katja Johansen.
Review Article|
February 05 2021
Rhizobia: highways to NO
Bryan Ruiz;
Bryan Ruiz
1Laboratoire des Interactions Plantes-Microbes-Environnement (LIPME), Université de Toulouse, INRA, CNRS, INSA, 31326 Castanet-Tolosan, France
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Åsa Frostegård
;
Åsa Frostegård
2Faculty of Chemistry, Biotechnology and Food Sciences, Norwegian University of Life Sciences, Ås, Norway
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Claude Bruand;
Claude Bruand
1Laboratoire des Interactions Plantes-Microbes-Environnement (LIPME), Université de Toulouse, INRA, CNRS, INSA, 31326 Castanet-Tolosan, France
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Eliane Meilhoc
1Laboratoire des Interactions Plantes-Microbes-Environnement (LIPME), Université de Toulouse, INRA, CNRS, INSA, 31326 Castanet-Tolosan, France
Correspondence: Eliane Meilhoc (Eliane.Meilhoc@inrae.fr)
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Publisher: Portland Press Ltd
Received:
October 16 2020
Revision Received:
January 06 2021
Accepted:
January 07 2021
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© 2021 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society
2021
Biochem Soc Trans (2021) 49 (1): 495–505.
Article history
Received:
October 16 2020
Revision Received:
January 06 2021
Accepted:
January 07 2021
Citation
Bryan Ruiz, Åsa Frostegård, Claude Bruand, Eliane Meilhoc; Rhizobia: highways to NO. Biochem Soc Trans 26 February 2021; 49 (1): 495–505. doi: https://doi.org/10.1042/BST20200989
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