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