title: Alterations in the mitochondrial alternative NAD(P)H Dehydrogenase NDB4 lead to changes in mitochondrial electron transport chain composition, plant growth and response to oxidative stress.
abstract: The branched respiratory electron transport chain of plants contains a non-phosphorylating alternative pathway consisting of type II NAD(P)H dehydrogenases on both sides of the inner membrane linked through the ubiquinone pool to an alternative oxidase (AOX). T-DNA and RNA interference (RNAi) were used to reduce gene expression to characterize the external NAD(P)H dehydrogenase NDB4 in Arabidopsis. The ndb4 lines showed different levels of suppression of NDB4 protein, leading to increases in NBD2 and AOX1a mRNA and protein levels in all lines. These changes were associated with lower reactive oxygen species formation and an altered phenotype, including changes in growth rate, root : shoot ratios and leaf area. The general growth pattern for the ndb4 mutants was decreased leaf area early in development (6-15 d) followed by a prompt subsequent increase in leaf area that exceeded the leaf area of the wild type by maturity (the 10-12 rosette stage). This pattern was most evident for the RNAi lines that had increased mitochondrial electron transport capacity. The RNAi lines also exhibited better tolerance to salinity stress, with better growth rates and lower shoot Na⁺ content compared with controls when grown under saline conditions. We hypothesize that these differences reflect the enhanced expression of NDB2 and AOX in the ndb4 mutant plants.
authors.affiliation: ARC Centre for Plant Energy Biology, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia.
authors.forename: Chevaun
authors.initials: C
authors.lastname: Smith
authors.forename: Michelle
authors.initials: M
authors.lastname: Barthet
authors.forename: Vanessa
authors.initials: V
authors.lastname: Melino
authors.forename: Penelope
authors.initials: P
authors.lastname: Smith
authors.forename: David
authors.initials: D
authors.lastname: Day
authors.forename: Kathleen
authors.initials: K
authors.lastname: Soole
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D019069:Cell Respiration; D004269:DNA, Bacterial / Q000235:genetics; D045222:Electron Transport Chain Complex Proteins / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009252:NADPH Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D034622:RNA Interference; D017382:Reactive Oxygen Species / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological; D000099188:Alternative Oxidase
chemical_list: D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D045222:Electron Transport Chain Complex Proteins; D024101:Mitochondrial Proteins; D009252:NADPH Dehydrogenase; D010088:Oxidoreductases; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D012965:Sodium Chloride; D000099188:Alternative Oxidase; C036483:T-DNA