The Transcription Factors WRKY11 and WRKY17 Act as Negative Regulators of Basal Resistance in Arabidopsis thaliana

Abstract

Transcription factors are believed to play a pivotal role in the activation and fine-tuning of plant defense responses, but little is known about the exact function of individual transcription factors in this process. We analyzed the role of the IId subfamily of WRKY transcription factors in the regulation of basal resistance to Pseudomonas syringae pv tomato (Pst). The expression of four members of the subfamily was induced upon challenge with virulent and avirulent strains of Pst. Mutant analyses revealed that loss of WRKY11 function increased resistance toward avirulent and virulent Pst strains and that resistance was further enhanced in wrky11 wrky17 double mutant plants. Thus, WRKY11 and WRKY17 act as negative regulators of basal resistance to Pst. Genome-wide expression analysis and expression studies of selected genes in single and double mutants demonstrated that both transcription factors modulate transcriptional changes in response to pathogen challenge. Depending on the target gene, WRKY11 and WRKY17 act either specifically or in a partially redundant manner. We demonstrate complex cross-regulation within the IId WRKY subfamily and provide evidence that both WRKY transcription factors are involved in the regulation of Pst-induced jasmonic acid-dependent responses. These results provide genetic evidence for the importance of WRKY11 and WRKY17 in plant defense.

The Role of WRKY Transcription Factors in Plant Immunity

“…Showing functional redundancy, Atwrky7 along with Atwrky11 and Atwrky17 mutants were susceptible to virulent P. syringae (Journot-Catalino et al, 2006;Kim et al, 2006). Similarly, AtWRKY38 and AtWRKY62 also contribute negatively to basal resistance toward this bacterial pathogen (Kim et al, 2008).…”

Two linked pairs of Arabidopsis TNL resistance genes independently confer recognition of bacterial effector AvrRps4

“…Both RRS1 and RRS1B carry WRKY domains in their C-termini. WRKY domain-containing proteins play crucial roles in regulating plant defence 50 . If AvrRps4 and PopP2 virulence activities are to target WRKY domaincontaining proteins, we could hypothesize that RRS1 and RRS1B, in association with RPS4 and RPS4B, respectively, could behave as decoys for effectors 44,51 .…”

Cross Talk in Defense Signaling

“…In a double mutant in which WRKY11 and WRKY17 were knocked out, transcripts of SA-responsive genes accumulated to higher levels, whereas those of JA-responsive genes were notably lower. Expression of WRKY70 was up-regulated in this double mutant, suggesting that WRKY11 and WRKY17 function as negative regulators of WRKY70 (Journot-Catalino et al, 2006). Recently, WRKY62 was added to the list of WRKY transcription factors with a putative role in SA/JA cross talk.…”