The Extensin Multigene Family Responds Differentially to Superoxide or Hydrogen Peroxide in Tomato Cell Cultures

FEBS Lett. 1999 Mar 26;447(2-3):264-8. doi: 10.1016/s0014-5793(99)00315-4.


Changes in extensin gene expression were examined in cultured tomato cells following treatments leading to the production of activated oxygen species. Digitonin, a steroid glycoalkaloid compound, has been shown to trigger a rapid and transient production of superoxide anion, O2-*. 6 h after application of 50 or 100 microM of digitonin, the accumulation of four extensin transcripts (1.5, 2.6, 4.0 and 6.1 kb) was observed. Superoxide dismutase strongly inhibited the digitonin-mediated response, suggesting a key role of O2-* in the signalling cascade. Furthermore, cells treated with enzymatically produced O2-* generated by xanthine oxidase (0.015 U/ml) gave a similar extensin response and again, SOD exerted a strong inhibitory effect on the response. On the other hand, H2O2 (2 mM) or the enzymatic H2O2 generator, glucose oxidase (0.34 U/ml), elicited the accumulation of only three of the four transcripts (1.5, 2.6 and 4.0 kb), indicating that the corresponding genes could be regulated either by H2O2 or O2-* but that the gene encoding the 6.1 kb transcript was exclusively expressed in response to O2-*. Finally, it was shown that lipid peroxidation, which was only induced when cells were exposed to H2O2, did not participate in the AOS-mediated gene expression for extensin. It can be concluded from these results that tomato cells are able to discriminate H2O2 from O2-* and they probably sense the latter by the specific oxidation of an extracellular component.

MeSH terms

  • Cells, Cultured
  • Digitonin / pharmacology
  • Gene Expression / drug effects
  • Genes, Plant / drug effects*
  • Glycoproteins / genetics*
  • Hydrogen Peroxide / metabolism
  • Hydrogen Peroxide / pharmacology*
  • Lipid Peroxidation / drug effects
  • Lycopersicon esculentum / drug effects
  • Lycopersicon esculentum / genetics
  • Lycopersicon esculentum / metabolism
  • Multigene Family / drug effects*
  • Plant Proteins / genetics*
  • Superoxides / metabolism
  • Superoxides / pharmacology*


  • Glycoproteins
  • Plant Proteins
  • extensin protein, plant
  • Superoxides
  • Hydrogen Peroxide
  • Digitonin