Role of Nitrate reductases and hemoglobins in the control nitric oxide homeostasis throughout the nitrogen-fixing symbiosis

Abstract

Nitric oxide (NO) is a gaseous signaling molecule with a broad spectrum of regulatory functions in plant and animal growth and development. It is involved in plant response to abiotic stress, including hypoxia, and biotic interactions such as nitrogen-fixing symbiosis (NFS) between legumes and soil gram-negative bacteria of rhizobium type. The interaction between legumes and rhizobia leads to the formation of new differentiated organs named nodules, which provide a niche for bacterial nitrogen fixation. Nitric oxide (NO) accumulates at each stage of the symbiotic process. NO is involved in defense responses, nodule organogenesis and development, nitrogen fixation metabolism, and senescence induction. During symbiosis, either successively or simultaneously, NO regulates gene expression, modulates enzyme activities, and acts as a metabolic intermediate in energy regeneration processes via phytoglobin-NO respiration and the bacterial denitrification pathway. The chemical nature, concentration and location of NO determine its either signalling, toxic or metabolic functions. This presentation will investigate NO source and degradation pathways, and highlights the role of nitrate reductases and haemoproteins of both the plant and bacterial partners in the control of NO accumulation throughout the nitrogen-fixing symbiotic process.

Concernant les jauges etc... pas de nouvelle mesure annoncée donc on reste sur une limite de 35 personnes en A010 et on devrait envoyer rapidement un lien ZOOM.