title: NPR1-independent activation of immediate early salicylic acid-responsive genes in Arabidopsis.
abstract: Salicylic acid (SA) is a key signal for the activation of defense genes in response to stress. The activation of late defense genes by SA, such as PR-1, involves the participation of the NPR1 protein. This protein acts as coactivator of the TGA factors that recognize as-1-like elements in the PR-1 promoter. Considering that functional as-1-like elements are also found in the promoter of SA- and auxin-responsive immediate early genes, we tested the hypothesis that NPR1 is also required for activation of these genes. The expression of the immediate early genes glutathione S-transferase (GST6) and glucosyltransferase (EIGT) was studied in npr1 mutant and wild-type Arabidopsis plants. In the npr1 mutant background, SA and 2,4-dichlorophenoxyacetic acid were unable to promote transcription of PR-1 but effectively stimulated the expression of GST6 and EIGT. Furthermore, increased binding of proteins to the GST6 as-1-like promoter element was detected in nuclear extracts from npr1 and wild-type plants after treatment with SA. In summary, these results indicate that activation of immediate early genes by SA proceeds through an NPR1-independent pathway. Therefore, we propose that activation by SA of immediate early and late genes occur by different mechanisms.
authors.affiliation: Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, P.O. Box 114-D, Santiago, Chile.
authors.forename: Carolina
authors.initials: C
authors.lastname: Uquillas
authors.forename: Ingrid
authors.initials: I
authors.lastname: Letelier
authors.forename: Francisca
authors.initials: F
authors.lastname: Blanco
authors.forename: Xavier
authors.initials: X
authors.lastname: Jordana
authors.forename: Loreto
authors.initials: L
authors.lastname: Holuigue
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D020156:Salicylic Acid / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D015084:2,4-Dichlorophenoxyacetic Acid; D029681:Arabidopsis Proteins; D005964:Glucosyltransferases; D005982:Glutathione Transferase; D020156:Salicylic Acid; C105496:NPR1 protein, Arabidopsis; C077262:PR-1 protein, Arabidopsis; C478067:At1g02930 protein, Arabidopsis