Department of Plant and Microbial Biology, Microbial and Plant Genomics Institute, University of Minnesota, 1500 Gortner Ave., Saint Paul, MN, 55108, USA.
New Phytol. 2018 Jan;217(2):700-712. doi: 10.1111/nph.14846. Epub 2017 Oct 27.
SARD1 is an activator of plant immunity that promotes production of the hormone salicylic acid (SA) and activation of defense gene expression. SARD1 itself is strongly inducible by infection. Here, we investigated the transcriptional control of SARD1. We used yeast one-hybrid assays to identify WRKY70. The WRKY70 binding site was defined using electrophoretic mobility shift assays, and its importance was investigated using an Arabidopsis thaliana protoplast system. The effect of wrky70 mutations was studied by measurements of pathogen growth, SA concentrations, and gene expression by RNA-seq. WRKY70 binds to a GACTTTT motif in the SARD1 promoter in yeast and Arabidopsis protoplasts. Plants with wrky70 mutations have elevated expression of SARD1 in the absence of pathogens, but not when infected. Expression profiling revealed that WRKY70 represses many pathogen-inducible genes in the absence of pathogens, yet is required for activation of many other pathogen-inducible genes in infected plants. The GACTTTT motif is enriched in the promoters of both these gene sets, and conserved in SARD1 orthologs within the Brassicaceae. WRKY70 represses SARD1 by binding the motif GACTTTT in the absence of pathogens. Conservation of the WRKY70 binding among the Brassicaceae suggests that WRKY70 repression of SARD1 is important for fitness.
SARD1 是一种植物免疫激活因子，可促进激素水杨酸（SA）的产生和防御基因表达的激活。SARD1 本身可被感染强烈诱导。在这里，我们研究了 SARD1 的转录控制。我们使用酵母单杂交试验来鉴定 WRKY70。使用电泳迁移率变动分析确定 WRKY70 结合位点，并使用拟南芥原生质体系统研究其重要性。通过测量病原体生长、SA 浓度和 RNA-seq 测量的基因表达，研究了 wrky70 突变的影响。WRKY70 在酵母和拟南芥原生质体中结合 SARD1 启动子中的 GACTTTT 基序。在没有病原体的情况下，wrky70 突变体植物中 SARD1 的表达升高，但在感染时则不然。表达谱分析表明，WRKY70 在没有病原体的情况下抑制许多病原体诱导的基因的表达，但在感染的植物中，它是激活许多其他病原体诱导的基因所必需的。该 GACTTTT 基序在这两组基因的启动子中均丰富，并在 Brassicaceae 中的 SARD1 同源物中保守。WRKY70 通过在没有病原体的情况下结合基序 GACTTTT 来抑制 SARD1。WRKY70 在 Brassicaceae 中的结合保守性表明，WRKY70 对 SARD1 的抑制对于适应性很重要。
