Principles and characteristics of the Arabidopsis WRKY regulatory network during early MAMP‐triggered immunity

Abstract

During microbe-associated molecular pattern-triggered immunity more than 5000 Arabidopsis genes are significantly altered in their expression, and the question arises, how such an enormous reprogramming of the transcriptome can be regulated in a safe and robust manner? For the WRKY transcription factors (TFs), which are important regulators of numerous defense responses, it appears that they act in a complex regulatory sub-network rather than in a linear fashion, which would be much more vulnerable to gene function loss either by pathogen-derived effectors or by mutations. In this study we employed RNA-seq, mass spectrometry and chromatin immunoprecipitation-seq to find evidence for and uncover principles and characteristics of this network. Upon flg22-treatment, one can distinguish between two sets of WRKY genes: constitutively expressed and induced WRKY genes. Prior to elicitation the induced WRKY genes appear to be maintained in a repressed state mainly by the constitutively expressed WRKY factors, which themselves appear to be regulated by non-WRKY TFs. Upon elicitation, induced WRKYs rapidly bind to induced WRKY gene promoters and by auto- and cross-regulation build up the regulatory network. Maintenance of this flg22-induced network appears highly robust as removal of three key WRKY factors can be physically and functionally compensated for by other WRKY family members.

The TIR-NB-LRR pair DSC1 and WRKY19 contributes to basal immunity of Arabidopsis to the root-knot nematode Meloidogyne incognita

“…A role for DSC1 and WRKY19 in basal immunity is consistent with observations by others that DSC1 transcript levels increase upon application of SA (salicylic acid) or flg22 (flagellin 22) [57] and that WRKY19 is thought to be an early component in regulatory networks of PTI [58]. Likewise, other TIR-NB-LRR proteins have been found to contribute to basal defense in Arabidopsis against Pseudomonas syringae (TN13) and the hemibiotrophic fungus Leptosphaeria maculans (RLM3) [59,60].…”

The transcriptional reprograming and functional identification of WRKY family members in pepper’s response to Phytophthora capsici infection

“…AtWRKY genes were down-regulated [31]. Naveed et al also revealed that most of the TFs from Carrizo citrange, such as ERF, bZIP and DOF, showed mixed trend of upand down-regulation, whereas most of the WRKY TFs were up-regulated during the P. parasitica infection [32].…”

Susceptibility genes, a novel strategy to improve resistance against the root-knot nematode Meloidogyne incognita

“…A role for DSC1 and WRKY19 in basal immunity is consistent with observations by others that DSC1 transcript levels increase upon application of SA or flg22 (Meyers et al, 2003) and that WRKY19 is thought to be an early component in regulatory networks of PTI (Birkenbihl et al, 2018). Likewise, other TIR-NLR proteins have been found to contribute to basal defense in Arabidopsis against Pseudomonas syringae (TN13) and a necrotrophic fungus (RLM3) (Staal & Dixelius, 2008;Roth et al, 2017).…”