title: Physiological and metabolic consequences of autophagy deficiency for the management of nitrogen and protein resources in Arabidopsis leaves depending on nitrate availability.
abstract: Autophagy is present at a basal level in all plant tissues and is induced during leaf ageing and in response to nitrogen (N) starvation. Nitrogen remobilization from the rosette to the seeds is impaired in autophagy mutants. This report focuses on the role of autophagy in leaf N management and proteolysis during plant ageing. Metabolites, enzyme activities and protein contents were monitored in several autophagy-defective (atg) Arabidopsis mutants grown under low and high nitrate conditions. Results showed that carbon (C) and N statuses were affected in atg mutants before any senescence symptoms appeared. atg mutants accumulated larger amounts of ammonium, amino acids and proteins than wild type, and were depleted in sugars. Over-accumulation of proteins in atg mutants was selective and occurred despite higher endopeptidase and carboxypeptidase activities. Specific over-accumulation of the ribosomal proteins S6 and L13 subunits, and of catalase and glutamate dehydrogenase proteins was observed. atg mutants also accumulated peptides putatively identified as degradation products of the Rubisco large subunit and glutamine synthetase 2 (GS2). Incomplete chloroplast protein degradation resulting from autophagy defects could explain the higher N concentrations measured in atg rosettes and defects in N remobilization. It is concluded that autophagy controls C : N status and protein content in leaves of Arabidopsis.
authors: UMR1318, INRA, Institut Jean-Pierre Bourgin, RD10, 78026, Versailles Cedex, France.
authors: Anne
authors: A
authors: Guiboileau
authors: Liliana
authors: L
authors: Avila-Ospina
authors: Kohki
authors: K
authors: Yoshimoto
authors: Fabienne
authors: F
authors: Soulay
authors: Marianne
authors: M
authors: Azzopardi
authors: Anne
authors: A
authors: Marmagne
authors: Jérémy
authors: J
authors: Lothier
authors: Céline
authors: C
authors: Masclaux-Daubresse
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001343:Autophagy / Q000187:drug effects; D018533:Biomass; D015153:Blotting, Western; D050260:Carbohydrate Metabolism / Q000187:drug effects; D002244:Carbon / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009566:Nitrates / Q000494:pharmacology*; D009584:Nitrogen / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D059748:Proteolysis / Q000187:drug effects; D034622:RNA Interference / Q000187:drug effects
chemical_list: D029681:Arabidopsis Proteins; D009566:Nitrates; D002244:Carbon; D010447:Peptide Hydrolases; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen
keywords: aminopeptidase; carboxypeptidase; leaf senescence; nitrate availability; nitrogen remobilization; selective autophagy