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Gene Review

AOX2  -  alternative oxidase 2

Arabidopsis thaliana

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Disease relevance of AOX2


High impact information on AOX2

  • We have positionally cloned IM and found that the gene encodes a 40.5-kD protein with sequence motifs characteristic of alternative oxidase, a mitochondrial protein that functions as a terminal oxidase in the respiratory chains of all plants [6].
  • Transgenic cultured tobacco cells with altered levels of AOX were used to test the hypothesis that the alternative pathway in plant mitochondria functions as a mechanism to decrease the formation of reactive oxygen species (ROS) produced during respiratory electron transport [7].
  • Also, the abundance of mRNAs encoding salicylic acid-binding catalase and a pathogenesis-related protein were significantly higher in cells deficient in AOX [7].
  • The clone encodes the gene for Arabidopsis alternative oxidase, whose deduced amino acid sequence was found to have 71% identity with that of the enzyme from the voodoo lily, Sauromatum guttatum [1].
  • Introduction of this pathway now opens the way to genetic/molecular biological investigations of alternative oxidase and its cofactor [1].

Chemical compound and disease context of AOX2


Biological context of AOX2

  • Comparison between genomic and cDNA sequences of the four AOX genes showed that all AOX genes are divided by three introns and the positions of the introns in AOX1a, AOX1b, AOX1c and AOX2 are the same [9].
  • A 5'RACE analysis showed that AOX2 consists of five exons, which is different from the case of most AOX genes identified so far [10].
  • We examined whether expression of Arabidopsis AOX genes, like the tobacco AOX1a gene, is enhanced by treatment with antimycin A, an inhibitor of complex III in the mitochondrial respiratory chain [9].
  • A revised model of the active site of alternative oxidase [11].
  • Interestingly, two of the AOX genes (AOX1a and AOX1b) were located in tandem in a ca. 5 kb region on one of the chromosomes of Arabidopsis [9].

Anatomical context of AOX2

  • Analysis of subcellular localization of AOX2 using green fluorescent protein indicated that the AOX2 protein is imported into the mitochondria [10].
  • Reduction and reoxidation of a sample of isolated E. coli membranes containing the alternative oxidase generated an EPR signal characteristic of a mixed-valent Fe(II)/Fe(III) binuclear iron center [8].
  • The Arabidopsis IMMUTANS gene encodes a plastid homolog of the mitochondrial alternative oxidase, which is associated with phytoene desaturation [12].
  • Comparison of the response of these two isozymes to pyruvate in isolated yeast mitochondria and disrupted mitochondrial membranes reveals that in contrast to At-AOX1a, Sg-AOX activity is insensitive to pyruvate and appears to be in a constitutively active state [13].

Associations of AOX2 with chemical compounds

  • We found that, in young plants, the amount of Arabidopsis AOX1a mRNA was dramatically increased by addition of antimycin A, while the transcription of the other three genes (AOX1b, AOX1c and AOX2) did not respond to antimycin A [9].
  • The plant mitochondrial protein alternative oxidase catalyses dioxygen dependent ubiquinol oxidation to yield ubiquinone and water [11].
  • The alternative oxidase is the first integral membrane protein in this family, and adds a new catalytic activity (ubiquinol oxidation) to this group of enzymatically diverse proteins [8].
  • In AOX containing a mutation of a putative glutamate ligand of the diiron center (E222A or E273A) the EPR signals are absent [8].
  • AOX can use reductant in excess of cytochrome pathway capacity, preventing reactive oxygen species (ROS) formation from an over-reduced ubiquinone pool, and thus may be involved in acclimation to oxidative stresses [14].

Analytical, diagnostic and therapeutic context of AOX2

  • A Northern blot analysis showed that AOX2 mRNA has already accumulated in dry seeds and subsequently decreased, whereas accumulation ofAOX1a mRNA was less abundant from 0 hours to 48 hours after imbibition and then increased [10].
  • We investigated the copy number of the gene for alternative oxidase (AOX) of Arabidopsis thaliana by amplification by PCR and Southern hybridization [9].
  • Laser-scanning confocal microscopy showed that the difference in ROS abundance among wild-type and AOX transgenic cells was caused by changes in mitochondrial-specific ROS formation [7].
  • The expression patterns of the GUS reporter genes in soybean cells were in agreement with the presence or absence of the various endogenous Aox proteins, determined by immunoblotting [15].
  • Addition of an AOX inhibitor to Arabidopsis cell cultures resulted in dramatically increased NO-sensitivity and cell death [3].


  1. Arabidopsis alternative oxidase sustains Escherichia coli respiration. Kumar, A.M., Söll, D. Proc. Natl. Acad. Sci. U.S.A. (1992) [Pubmed]
  2. Enhanced expression and activation of the alternative oxidase during infection of Arabidopsis with Pseudomonas syringae pv tomato. Simons, B.H., Millenaar, F.F., Mulder, L., Van Loon, L.C., Lambers, H. Plant Physiol. (1999) [Pubmed]
  3. Nitric oxide induces transcriptional activation of the nitric oxide-tolerant alternative oxidase in Arabidopsis suspension cells. Huang, X., von Rad, U., Durner, J. Planta (2002) [Pubmed]
  4. Salicylic acid-induced resistance to Cucumber mosaic virus in squash and Arabidopsis thaliana: contrasting mechanisms of induction and antiviral action. Mayers, C.N., Lee, K.C., Moore, C.A., Wong, S.M., Carr, J.P. Mol. Plant Microbe Interact. (2005) [Pubmed]
  5. Overexpression of wheat alternative oxidase gene Waox1a alters respiration capacity and response to reactive oxygen species under low temperature in transgenic Arabidopsis. Sugie, A., Naydenov, N., Mizuno, N., Nakamura, C., Takumi, S. Genes Genet. Syst. (2006) [Pubmed]
  6. The IMMUTANS variegation locus of Arabidopsis defines a mitochondrial alternative oxidase homolog that functions during early chloroplast biogenesis. Wu, D., Wright, D.A., Wetzel, C., Voytas, D.F., Rodermel, S. Plant Cell (1999) [Pubmed]
  7. The alternative oxidase lowers mitochondrial reactive oxygen production in plant cells. Maxwell, D.P., Wang, Y., McIntosh, L. Proc. Natl. Acad. Sci. U.S.A. (1999) [Pubmed]
  8. EPR studies of the mitochondrial alternative oxidase. Evidence for a diiron carboxylate center. Berthold, D.A., Voevodskaya, N., Stenmark, P., Gräslund, A., Nordlund, P. J. Biol. Chem. (2002) [Pubmed]
  9. Characterization of the gene family for alternative oxidase from Arabidopsis thaliana. Saisho, D., Nambara, E., Naito, S., Tsutsumi, N., Hirai, A., Nakazono, M. Plant Mol. Biol. (1997) [Pubmed]
  10. The gene for alternative oxidase-2 (AOX2) from Arabidopsis thaliana consists of five exons unlike other AOX genes and is transcribed at an early stage during germination. Saish, D., Nakazono, M., Lee, K.H., Tsutsumi, N., Akita, S., Hirai, A. Genes Genet. Syst. (2001) [Pubmed]
  11. A revised model of the active site of alternative oxidase. Andersson, M.E., Nordlund, P. FEBS Lett. (1999) [Pubmed]
  12. A plastid terminal oxidase associated with carotenoid desaturation during chromoplast differentiation. Josse, E.M., Simkin, A.J., Gaffé, J., Labouré, A.M., Kuntz, M., Carol, P. Plant Physiol. (2000) [Pubmed]
  13. Constitutive activity of Sauromatum guttatum alternative oxidase in Schizosaccharomyces pombe implicates residues in addition to conserved cysteines in alpha-keto acid activation. Crichton, P.G., Affourtit, C., Albury, M.S., Carré, J.E., Moore, A.L. FEBS Lett. (2005) [Pubmed]
  14. Characterization of transformed Arabidopsis with altered alternative oxidase levels and analysis of effects on reactive oxygen species in tissue. Umbach, A.L., Fiorani, F., Siedow, J.N. Plant Physiol. (2005) [Pubmed]
  15. Analysis of the alternative oxidase promoters from soybean. Thirkettle-Watts, D., McCabe, T.C., Clifton, R., Moore, C., Finnegan, P.M., Day, D.A., Whelan, J. Plant Physiol. (2003) [Pubmed]
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