title: The extensin multigene family responds differentially to superoxide or hydrogen peroxide in tomato cell cultures.
abstract: 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.
authors.affiliation: CEA, CE de Cadarache, Département de Physiologie Végétale and de Microbiologie Végétale, St Paul-lez-Durance, France.
authors.forename: J P
authors.initials: JP
authors.lastname: Wisniewski
authors.forename: P
authors.initials: P
authors.lastname: Cornille
authors.forename: J P
authors.initials: JP
authors.lastname: Agnel
authors.forename: J L
authors.initials: JL
authors.lastname: Montillet
mesh_terms: D002478:Cells, Cultured; D004072:Digitonin / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D017343:Genes, Plant / Q000187:drug effects*; D006023:Glycoproteins / Q000235:genetics*; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology*; D015227:Lipid Peroxidation / Q000187:drug effects; D018551:Solanum lycopersicum / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D005810:Multigene Family / Q000187:drug effects*; D010940:Plant Proteins / Q000235:genetics*; D013481:Superoxides / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D006023:Glycoproteins; D010940:Plant Proteins; C005488:extensin protein, plant; D013481:Superoxides; D006861:Hydrogen Peroxide; D004072:Digitonin