Ensifer meliloti denitrification is involved in infection effectiveness and N2O emissions from alfalfa root nodules
Purpose: Alfalfa is one of the most valuable forage crops in temperate climate zones. Ensifer meliloti, the endosymbiont of alfalfa, contains all the denitrification genes but the capacity of alfalfa root nodules to produce nitrous oxide (NO) is not known. In this work, NO emissions as well as the i...
| Autores: | , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2023 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/332034 |
| Acceso en línea: | http://hdl.handle.net/10261/332034 |
| Access Level: | acceso abierto |
| Palabra clave: | Alfalfa Copper Legume-rhizobia symbiosis Nitrous oxide emissions Nodulation competitiveness |
| Sumario: | Purpose: Alfalfa is one of the most valuable forage crops in temperate climate zones. Ensifer meliloti, the endosymbiont of alfalfa, contains all the denitrification genes but the capacity of alfalfa root nodules to produce nitrous oxide (NO) is not known. In this work, NO emissions as well as the influence of bacteroidal denitrification on nodulation competitiveness and NO release from alfalfa nodules has been investigated. Methods: Medicago sativa cv. Victoria plants were inoculated with E. meliloti 1021, a periplasmic nitrate reductase (Nap) defective mutant, a Nap overexpressing strain and a nitrous oxide reductase defective mutant. Plants were grown in the presence of different nitrate and copper treatments and subjected to flooding during one week before harvesting. NO production by the nodules was analysed by using gas chromatography. Methyl viologen-dependent nitrate reductase (MV-NR), nitrite reductase (MV-NIR) and nitrous oxide reductase (NOR) enzymatic activities were measured in isolated bacteroids. Results: Alfalfa root nodules produce NO in response to nitrate and flooding. Overexpression of Nap improved nodulation competitiveness and induced NO emissions from nodules. Copper is required for an effective symbiosis as well as triggered a reduction of NO production due to the induction of the NOR and a reduction of NIR activities in the bacteroids. Conclusion: Alfalfa root nodules emit NO. Nap is involved in nodulation competitiveness and in NO emissions by the nodules. Bacteroidal NOR and NIR activities are modulated by Cu and may be considered as effective targets for the mitigation strategies of NO emissions derived from alfalfa crops. |
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