title: Inhibition of aconitase by nitric oxide leads to induction of the alternative oxidase and to a shift of metabolism towards biosynthesis of amino acids.
abstract: Nitric oxide (NO) is a free radical molecule involved in signalling and in hypoxic metabolism. This work used the nitrate reductase double mutant of Arabidopsis thaliana (nia) and studied metabolic profiles, aconitase activity, and alternative oxidase (AOX) capacity and expression under normoxia and hypoxia (1% oxygen) in wild-type and nia plants. The roots of nia plants accumulated very little NO as compared to wild-type plants which exhibited ∼20-fold increase in NO emission under low oxygen conditions. These data suggest that nitrate reductase is involved in NO production either directly or by supplying nitrite to other sites of NO production (e.g. mitochondria). Various studies revealed that NO can induce AOX in mitochondria, but the mechanism has not been established yet. This study demonstrates that the NO produced in roots of wild-type plants inhibits aconitase which in turn leads to a marked increase in citrate levels. The accumulating citrate enhances AOX capacity, expression, and protein abundance. In contrast to wild-type plants, the nia double mutant failed to show AOX induction. The overall induction of AOX in wild-type roots correlated with accumulation of glycine, serine, leucine, lysine, and other amino acids. The findings show that NO inhibits aconitase under hypoxia which results in accumulation of citrate, the latter in turn inducing AOX and causing a shift of metabolism towards amino acid biosynthesis.
authors.affiliation: Department of Plant Physiology, University of Rostock, Albert Einstein Str. 3, D-18059, Rostock, Germany. jagadis.kapuganti@uni-rostock.de
authors.forename: Kapuganti J
authors.initials: KJ
authors.lastname: Gupta
authors.forename: Jay K
authors.initials: JK
authors.lastname: Shah
authors.forename: Yariv
authors.initials: Y
authors.lastname: Brotman
authors.forename: Kathrin
authors.initials: K
authors.lastname: Jahnke
authors.forename: Lothar
authors.initials: L
authors.lastname: Willmitzer
authors.forename: Werner M
authors.initials: WM
authors.lastname: Kaiser
authors.forename: Hermann
authors.initials: H
authors.lastname: Bauwe
authors.forename: Abir U
authors.initials: AU
authors.lastname: Igamberdiev
mesh_terms: D000154:Aconitate Hydratase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000596:Amino Acids / Q000096:biosynthesis*; D017360:Arabidopsis / Q000201:enzymology / Q000378:metabolism*; D019343:Citric Acid / Q000378:metabolism; D004790:Enzyme Induction; D018506:Gene Expression Regulation, Plant; D005822:Genetic Vectors; D005838:Genotype; D024101:Mitochondrial Proteins / Q000096:biosynthesis* / Q000378:metabolism; D050901:Nitrate Reductase / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D010088:Oxidoreductases / Q000096:biosynthesis* / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism; D010940:Plant Proteins / Q000096:biosynthesis* / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D015398:Signal Transduction; D000099188:Alternative Oxidase
chemical_list: D000154:Aconitate Hydratase; D000596:Amino Acids; D019343:Citric Acid; D024101:Mitochondrial Proteins; D050901:Nitrate Reductase; D009569:Nitric Oxide; D010088:Oxidoreductases; D010937:Plant Growth Regulators; D010940:Plant Proteins; D000099188:Alternative Oxidase