Functional analysis of regulatory sequences controllingPR‐1 gene expression in Arabidopsis

Abstract

SummaryThe Arabidopsis PR-1 gene is one of a suite of genes induced co-ordinately during the onset of systemic acquired resistance (SAR), a plant defense pathway triggered by pathogen infection or exogenous application of chemicals such as salicylic acid (SA) and 2,6-dichloroisonicotinic acid (INA). We have characterized cis-acting regulatory elements in the PR-1 promoter involved in INA induction using deletion analysis, linker-scanning mutagenesis, and in vivo footprinting. Compared to promoter fragments of 815 bp or longer (which show greater than 10-fold inducibility after INA treatment), induction of a 698 bp long promoter fragment is reduced by half and promoter fragments of 621 bp or shorter have lost all inducibility. Additionally, two 10-bp linker-scanning mutations centered at 640 bp and 610 bp upstream from the transcription initiation site are each sufficient to abolish chemical inducibility of a GUS reporter fusion. The -640 linker-scanning mutation encompasses a region highly homologous to recognition sites for transcription factors of the basic leucine zipper class, while the -610 linker-scanning mutation contains a sequence similar to a consensus recognition site for the transcription factor NF-κB. Furthermore, several inducible in vivo footprints located at or nearby these motifs demonstrate significant and highly reproducible changes in DNA accessibility following SAR induction. This in vivo signature of protein-DNA interactions after INA induction is tightly correlated with the functionally important regions of the promoter identified by mutation analysis.

In Vivo Interaction between NPR1 and Transcription Factor TGA2 Leads to Salicylic Acid–Mediated Gene Activation in Arabidopsis

“…Indeed, using yeast two-hybrid screens, we and others found that NPR1 interacts with the TGA subclass of basic Leu zipper (bZIP) transcription factors Després et al, 2000;Niggeweg et al, 2000b;Zhou et al, 2000;Chern et al, 2001), suggesting that TGA factors could be the missing link between NPR1 and its target genes. This notion is supported by several studies in which the binding sites for TGA transcription factors (e.g., the as-1 element) in PR gene promoters were found to be responsible for SA-mediated gene induction (Qin et al, 1994;Shah and Klessig, 1996;Lebel et al, 1998).…”

Safeners recruit multiple signalling pathways for the orchestrated induction of the cellular xenobiotic detoxification machinery in Arabidopsis

“…(PR) genes in plants (Lebel et al 1998). The regulated expression of these genes is mediated by TGA factors, a specific class of conserved bZip transcription factors (Jakoby et al 2002).…”

OsWRKY03, a rice transcriptional activator that functions in defense signaling pathway upstream of OsNPR1

“…Arabidopsis NPR1/NIM1 gene encodes a novel protein with ankyrin repeats [29], which is essential for NPR1 binding to the TGA basic leucine zipper transcription factors [33]. The interaction between NPR1 and TGA factors facilitates the binding of TGA proteins to the SA-responsive as-1 or as-1-like promoter elements, and leads to the activation of downstream genes during defense response [34,35].…”