title: Identification of a gene for pyruvate-insensitive mitochondrial alternative oxidase expressed in the thermogenic appendices in Arum maculatum.
abstract: Heat production in thermogenic plants has been attributed to a large increase in the expression of the alternative oxidase (AOX). AOX acts as an alternative terminal oxidase in the mitochondrial respiratory chain, where it reduces molecular oxygen to water. In contrast to the mitochondrial terminal oxidase, cytochrome c oxidase, AOX is nonprotonmotive and thus allows the dramatic drop in free energy between ubiquinol and oxygen to be dissipated as heat. Using reverse transcription-polymerase chain reaction-based cloning, we reveal that, although at least seven cDNAs for AOX exist (AmAOX1a, -1b, -1c, -1d, -1e, -1f, and -1g) in Arum maculatum, the organ and developmental regulation for each is distinct. In particular, the expression of AmAOX1e transcripts appears to predominate in thermogenic appendices among the seven AmAOXs. Interestingly, the amino acid sequence of AmAOX1e indicates that the ENV element found in almost all other AOX sequences, including AmAOX1a, -1b, -1c, -1d, and -1f, is substituted by QNT. The existence of a QNT motif in AmAOX1e was confirmed by nano-liquid chromatography-tandem mass spectrometry analysis of mitochondrial proteins from thermogenic appendices. Further functional analyses with mitochondria prepared using a yeast heterologous expression system demonstrated that AmAOX1e is insensitive to stimulation by pyruvate. These data suggest that a QNT type of pyruvate-insensitive AOX, AmAOX1e, plays a crucial role in stage- and organ-specific heat production in the appendices of A. maculatum.
authors: Cryobiofrontier Research Center, Faculty of Agriculture, Iwate University, Ueda, Morioka, Iwate 020-8550, Japan. kikuito@iwate-u.ac.jp
authors: Kikukatsu
authors: K
authors: Ito
authors: Takafumi
authors: T
authors: Ogata
authors: Yusuke
authors: Y
authors: Kakizaki
authors: Catherine
authors: C
authors: Elliott
authors: Mary S
authors: MS
authors: Albury
authors: Anthony L
authors: AL
authors: Moore
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D031058:Arum / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D001483:Base Sequence; D019069:Cell Respiration; D002853:Chromatography, Liquid; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D035264:Flowers / Q000201:enzymology* / Q000235:genetics; D006358:Hot Temperature; D024101:Mitochondrial Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010088:Oxidoreductases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D010940:Plant Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D019289:Pyruvic Acid / Q000494:pharmacology*; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D053719:Tandem Mass Spectrometry; D000099188:Alternative Oxidase
chemical_list: D018076:DNA, Complementary; D018744:DNA, Plant; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D019289:Pyruvic Acid; D000099188:Alternative Oxidase