A “Whirly” Transcription Factor Is Required for Salicylic Acid-Dependent Disease Resistance in Arabidopsis

Abstract

Transcriptional reprogramming is critical for plant disease resistance responses; its global control is not well understood. Salicylic acid (SA) can induce plant defense gene expression and a long-lasting disease resistance state called systemic acquired resistance (SAR). Plant-specific "Whirly" DNA binding proteins were previously implicated in defense gene regulation. We demonstrate that the potato StWhy1 protein is a transcriptional activator of genes containing the PBF2 binding PB promoter element. DNA binding activity of AtWhy1, the Arabidopsis StWhy1 ortholog, is induced by SA and is required for both SA-dependent disease resistance and SA-induced expression of an SAR response gene. AtWhy1 is required for both full basal and specific disease resistance responses. The transcription factor-associated protein NPR1 is also required for SAR. Surprisingly, AtWhy1 activation by SA is NPR1 independent, suggesting that AtWhy1 works in conjunction with NPR1 to transduce the SA signal. Our analysis of AtWhy1 adds a critical component to the SA-dependent plant disease resistance response.

NPR1: the spider in the web of induced resistance signaling pathways

“…Other essential transcription factors and their corresponding cis-acting elements have been identified, but their role in SAR still needs to be clarified. For instance, Desveaux et al [55] identified a 'Whirly' transcription factor in Arabidopsis that is activated by SA but functions independently of NPR1 in activating SA-responsive gene expression and SAR, demonstrating that this type of induced resistance is regulated in a complex manner. Second, the identification of critical factors that are involved in the synthesis and transmission of the yet unidentified long-distance signals opens up new possibilities for discovering the nature of these mobile signals and their role in systemic induced resistance.…”

The Single-Stranded DNA-Binding Protein WHIRLY1 Represses WRKY53 Expression and Delays Leaf Senescence in a Developmental Stage-Dependent Manner in Arabidopsis

“…The Arabidopsis genome encodes three WHY proteins: AtWHY1 and AtWHY3 contain plastid-targeting signal, whereas AtWHY2 localizes to mitochondria (Krause et al, 2005). Similar to StWHY1, AtWHY1 has been proven to have a relationship with disease resistance (Desveaux et al, 2004(Desveaux et al, , 2005. A number of potential WHY1 target genes were proposed based on the occurrence of ERE sequences in their promoters, but experimental data are lacking.…”

“…A number of potential WHY1 target genes were proposed based on the occurrence of ERE sequences in their promoters, but experimental data are lacking. Until now, only the PR1 gene has been proven to be downregulated as a result of a TILLING mutation in WHY1 in Arabidopsis (Desveaux et al, 2004(Desveaux et al, , 2005. Besides the activity as a transcriptional activator, AtWHY1 was also identified in a fraction of telomere-binding proteins, and its knockout mutant appeared to have a shorter telomere (Yoo et al, 2007).…”

The functions of WHIRLY1 and REDOX-RESPONSIVE TRANSCRIPTION FACTOR 1 in cross tolerance responses in plants: a hypothesis

“…Plants have a small family of single-stranded DNA binding proteins called WHIRLY that are also involved in the control of defence gene expression [56,57]. Although most plant species have two members, some species including Arabidopsis thaliana have three WHIRLY proteins.…”

“…As discussed above, high-light-dependent induction of SA signalling pathways requires redox changes and protein nitrosylation events that result in NPR1 movement into the nucleus [50,53]. However, WHIRLY1 was identified as a downstream component of SA signalling pathways that are independent of NPR1 [56]. It has been suggested that SA converts an inactive rstb.royalsocietypublishing.org Phil.…”