WRKY transcription factors are involved in brassinosteroid signaling and mediate the crosstalk between plant growth and drought tolerance

Brassinosteroids (BRs) are critical for the plant growth and development. BRs signal through the plasma membrane localized receptor-like kinases to downstream transcription factors BES1/BZR1 to regulate the expression of thousands of genes for various BR responses. In addition to the role in plant growth and development, BRs have been implicated in responses to environmental stresses such as drought. However, the mechanism through which BRs regulate drought have just begun emerging. We have recently found that a group of WRKY transcription factors, WRKY46, WRKY54, WRKY70, which are well known for the function in abiotic and biotic stress, cooperates with BES1 to mediate BR-regulated drought response. The wrky46 wrky54 wrky70 triple mutants showed growth defect, likely due to impaired BR signaling as well as some reduction of endogenous BR level. WRKY46/54/70 cooperates with BES1 to regulate the expression of BR target genes to promote growth. We also found that WRKY46/54/70 negatively modulates drought tolerance by globally repressing drought-inducible gene expression. Thus, our result uncovers a new role for WRKY transcription factors in BR signaling and provides the molecular mechanism for BR-regulated plant growth and drought stress through WRKY46/54/70 and BES1 transcription factors.