title: Metabolic and structural rearrangement during dark-induced autophagy in soybean (Glycine max L.) nodules: an electron microscopy and 31P and 13C nuclear magnetic resonance study.
abstract: The effects of dark-induced stress on the evolution of the soluble metabolites present in senescent soybean (Glycine max L.) nodules were analysed in vitro using (13)C- and (31)P-NMR spectroscopy. Sucrose and trehalose were the predominant soluble storage carbons. During dark-induced stress, a decline in sugars and some key glycolytic metabolites was observed. Whereas 84% of the sucrose disappeared, only one-half of the trehalose was utilised. This decline coincides with the depletion of Gln, Asn, Ala and with an accumulation of ureides, which reflect a huge reduction of the N(2) fixation. Concomitantly, phosphodiesters and compounds like P-choline, a good marker of membrane phospholipids hydrolysis and cell autophagy, accumulated in the nodules. An autophagic process was confirmed by the decrease in cell fatty acid content. In addition, a slight increase in unsaturated fatty acids (oleic and linoleic acids) was observed, probably as a response to peroxidation reactions. Electron microscopy analysis revealed that, despite membranes dismantling, most of the bacteroids seem to be structurally intact. Taken together, our results show that the carbohydrate starvation induced in soybean by dark stress triggers a profound metabolic and structural rearrangement in the infected cells of soybean nodule which is representative of symbiotic cessation.
authors.affiliation: Laboratory of Plant Biology and Physiology, Biology Building UNIL, Room 5449, 1015 Lausanne, Switzerland. pierre.vauclare@wanadoo.fr
authors.forename: Pierre
authors.initials: P
authors.lastname: Vauclare
authors.forename: Richard
authors.initials: R
authors.lastname: Bligny
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Gout
authors.forename: Valentine
authors.initials: V
authors.lastname: De Meuron
authors.forename: François
authors.initials: F
authors.lastname: Widmer
mesh_terms: D001343:Autophagy; D002247:Carbon Isotopes; D002462:Cell Membrane / Q000378:metabolism; D016922:Cellular Senescence; D003624:Darkness; D005227:Fatty Acids / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D055442:Metabolome; D008854:Microscopy, Electron; D010759:Phosphorus Isotopes; D053204:Root Nodules, Plant / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure*; D013025:Glycine max / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure*; D013312:Stress, Physiological
chemical_list: D002247:Carbon Isotopes; D005227:Fatty Acids; D010759:Phosphorus Isotopes