Functions and Mechanism of WRKY Transcription Factors in Brassinosteroid-Regulated Plant Growth and Stress Response

摘要

Brassinosteroids (BRs), a family of plant steroid hormones, play important role in plant growth and development. BR signal is perceived by receptors BRI1 and BAK1, which transduce the hormonal signal to downstream transcription factors BES1/BZR1 to regulate the expression of thousands of BR target genes. BRs also play a vital role in both abiotic and biotic stress responses. However, the molecular mechanisms by which BRs regulate stress responses have just begun to be revealed. Here, we characterized three group III transcription factors, WRKY46, WRKY 54 and WRKY70, which are involved in BR-regulated plant growth and drought stress by cooperating with BES1 to positively regulate BR target genes and negatively control drought-responsive genes. The stability of WRKY54 is regulated through phosphorylation by BIN2, a GSK3-like kinase that plays a negative role in BR-regulated plant growth. Moreover, we also characterized another three group III transcription factors, WRKY30, WRKY 41 and WRKY53, in bacterial defense response, which likely act through MAP kinase cascade-regulated Pathogen Associated Molecular Patterns (PAMP)-Triggered Immunity pathway. Our results thus revealed that group III WRKYs integrate the signals from BRs, drought and bacterial pathogens to regulate the expression of downstream growth-related and stress-responsive genes, which significantly advances our understanding of BR regulation of stress responses.