The as-1 promoter element is an oxidative stress-responsive element and salicylic acid activates it via oxidative species.
The activation sequence-1 (as-1)-like element found in the promoter of some glutathione S-transferase (GST) genes, has been previously described as a salicylic acid (SA)- and auxin-responsive element. In this paper, we tested the hypothesis that the activating effect of SA on the as-1 element is mediated by oxidative species. Supporting this hypothesis, our results show that the antioxidants dimethylthiourea (DMTU) and 3-t-butyl-4-hydroxy-anizole (BHA) inhibit the SA-induced transcription of genes controlled by as-1 elements in tobacco (Nicotiana tabacum) plants [i.e. GNT35 gene coding for a GST and (as-1)(4)/beta-glucuronidase (GUS) reporter transgene]. DMTU and BHA also inhibit SA-activated as-1-binding activity in nuclear extracts. Further support for the hypothesis that the as-1 element is activated by oxidative species comes from our result showing that light potentiates the SA-induced activation of the as-1 element. Furthermore, methyl viologen, a known oxidative stress inducer in plants, also activates the as-1 element. Increasing H(2)O(2) levels by incubation with H(2)O(2) or with the catalase inhibitor 3-amino-1,2,5-triazole does not activate the (as-1)(4)/GUS gene. On the contrary, 3-amino-1,2,5-triazole inhibits the activating effect of SA on the (as-1)(4)/GUS gene. These results suggest that oxidative species other than H(2)O(2) mediate the activation of the as-1 element by SA. Our results also suggest that even though the as-1 binding activity is stimulated by oxidative species, this is not sufficient for the transactivation of genes controlled by this element. The complex interplay between SA and reactive oxygen species in the transcriptional activation of defense genes is discussed.
Garretón
Virginia
V
Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago, Chile.
Carpinelli
Jorge
J
Jordana
Xavier
X
Holuigue
Loreto
L
D000640:Amitrole / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D001665:Binding Sites / Q000187:drug effects / Q000528:radiation effects; D002083:Butylated Hydroxyanisole / Q000494:pharmacology; D002374:Catalase / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008027:Light; D018384:Oxidative Stress; D010269:Paraquat / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020218:Response Elements / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D020156:Salicylic Acid / Q000494:pharmacology*; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology; D014026:Nicotiana / Q000187:drug effects / Q000235:genetics
D000975:Antioxidants; D004791:Enzyme Inhibitors; D017382:Reactive Oxygen Species; D002083:Butylated Hydroxyanisole; C038983:1,3-dimethylthiourea; D006861:Hydrogen Peroxide; D002374:Catalase; D005982:Glutathione Transferase; D013890:Thiourea; D020156:Salicylic Acid; D010269:Paraquat; D000640:Amitrole