title: Loss of Lon1 in Arabidopsis changes the mitochondrial proteome leading to altered metabolite profiles and growth retardation without an accumulation of oxidative damage.
abstract: Lon1 is an ATP-dependent protease and chaperone located in the mitochondrial matrix in plants. Knockout in Arabidopsis (Arabidopsis thaliana) leads to a significant growth rate deficit in both roots and shoots and lowered activity of specific mitochondrial enzymes associated with respiratory metabolism. Analysis of the mitochondrial proteomes of two lon1 mutant alleles (lon1-1 and lon1-2) with different severities of phenotypes shows a common accumulation of several stress marker chaperones and lowered abundance of Complexes I, IV, and V of OXPHOS. Certain enzymes of the tricarboxylic acid (TCA) cycle are modified or accumulated, and TCA cycle bypasses were repressed rather than induced. While whole tissue respiratory rates were unaltered in roots and shoots, TCA cycle intermediate organic acids were depleted in leaf extracts in the day in lon1-1 and in both lon mutants at night. No significant evidence of broad steady-state oxidative damage to isolated mitochondrial samples could be found, but peptides from several specific proteins were more oxidized and selected functions were more debilitated in lon1-1. Collectively, the evidence suggests that loss of Lon1 significantly modifies respiratory function and plant performance by small but broad alterations in the mitochondrial proteome gained by subtly changing steady-state protein assembly, stability, and damage of a range of components that debilitate an anaplerotic role for mitochondria in cellular carbon metabolism.
authors.affiliation: ARC Centre of Excellence in Plant Energy Biology and Centre for Comparative Analysis of Biomolecular Networks, University of Western Australia, Crawley, Washington 6009, Western Australia, Australia.
authors.forename: Cory
authors.initials: C
authors.lastname: Solheim
authors.forename: Lei
authors.initials: L
authors.lastname: Li
authors.forename: Polydefkis
authors.initials: P
authors.lastname: Hatzopoulos
authors.forename: A Harvey
authors.initials: AH
authors.lastname: Millar
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology / Q000254:growth & development* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D018533:Biomass; D019069:Cell Respiration; D002952:Citric Acid Cycle; D004579:Electron Transport; D015180:Electrophoresis, Gel, Two-Dimensional; D055442:Metabolome; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D020543:Proteome / Q000378:metabolism*; D040901:Proteomics; D012697:Serine Endopeptidases / Q000378:metabolism*; D013312:Stress, Physiological
chemical_list: D029681:Arabidopsis Proteins; D024101:Mitochondrial Proteins; D020543:Proteome; C579791:Lon1 protein, Arabidopsis; D012697:Serine Endopeptidases