Broad‐spectrum resistance gene RPW8.1 balances immunity and growth via feedback regulation of WRKYs

Summary Arabidopsis RESISTANCE TO POWDERY MILDEW 8.1 ( RPW8.1 ) is an important tool for engineering broad‐spectrum disease resistance against multiple pathogens. Ectopic expression of RPW8.1 leads to enhanced disease resistance with cell death at leaves and compromised plant growth, implying a regulatory mechanism balancing RPW8.1 ‐mediated resistance and growth. Here, we show that RPW8.1 constitutively enhances the expression of transcription factor WRKY51 and activates salicylic acid and ethylene signalling pathways; WRKY51 in turn suppresses RPW8.1 expression, forming a feedback regulation loop. RPW8.1 and WRKY51 are both induced by pathogen infection and pathogen−/microbe‐associated molecular patterns. In ectopic expression of RPW8.1 background ( R1Y4 ), overexpression of WRKY51 not only rescues the growth suppression and cell death caused by RPW8.1 , but also suppresses RPW8.1 ‐mediated broad‐spectrum disease resistance and pattern‐triggered immunity. Mechanistically, WRKY51 directly binds to and represses RPW8.1 promoter, thus limiting the expression amplitude of RPW8.1 . Moreover, WRKY6 , WRKY28 and WRKY41 play a role redundant to WRKY51 in the suppression of RPW8.1 expression and are constitutively upregulated in R1Y4 plants with WRKY51 being knocked out ( wrky51 R1Y4 ) plants. Notably, WRKY51 has no significant effects on disease resistance or plant growth in wild type without RPW8.1 , indicating a specific role in RPW8.1 ‐mediated disease resistance. Altogether, our results reveal a regulatory circuit controlling the accumulation of RPW8.1 to an appropriate level to precisely balance growth and disease resistance during pathogen invasion.