Graduate Institute of Plant Biology, National Taiwan University, Taipei, 10617, Taiwan.
Department of Life Science, College of Life Science, National Taiwan University, Taipei, 10617, Taiwan.
Mol Plant Pathol. 2017 Oct;18(8):1062-1074. doi: 10.1111/mpp.12460. Epub 2016 Sep 1.
Ethylene response factors (ERFs) are a large plant-specific transcription factor family and play diverse important roles in various plant functions. However, most tomato ERFs have not been characterized. In this study, we showed that the expression of an uncharacterized member of the tomato ERF-IX subgroup, ERF68, was significantly induced by treatments with different bacterial pathogens, ethylene (ET) and salicylic acid (SA), but only slightly induced by bacterial mutants defective in the type III secretion system (T3SS) or non-host pathogens. The ERF68-green fluorescent protein (ERF68-GFP) fusion protein was localized in the nucleus. Transactivation and electrophoretic mobility shift assays (EMSAs) further showed that ERF68 was a functional transcriptional activator and was bound to the GCC-box. Moreover, transient overexpression of ERF68 led to spontaneous lesions in tomato and tobacco leaves and enhanced the expression of genes involved in ET, SA, jasmonic acid (JA) and hypersensitive response (HR) pathways, whereas silencing of ERF68 increased tomato susceptibility to two incompatible Xanthomonas spp. These results reveal the involvement of ERF68 in the effector-triggered immunity (ETI) pathway. To identify ERF68 target genes, chromatin immunoprecipitation combined with high-throughput sequencing (ChIP-seq) was performed. Amongst the confirmed target genes, a few genes involved in cell death or disease defence were differentially regulated by ERF68. Our study demonstrates the function of ERF68 in the positive regulation of hypersensitive cell death and disease defence by modulation of multiple signalling pathways, and provides important new information on the complex regulatory function of ERFs.
乙烯应答因子（ERFs）是一类植物特有的转录因子家族，在各种植物功能中发挥着多样化的重要作用。然而，大多数番茄 ERFs 尚未被表征。在本研究中，我们表明，番茄 ERF-IX 亚组中一个未被表征成员 ERF68 的表达，受到不同细菌病原体、乙烯（ET）和水杨酸（SA）处理的显著诱导，但仅受到 III 型分泌系统（T3SS）缺陷的细菌突变体或非宿主病原体的轻微诱导。ERF68-绿色荧光蛋白（ERF68-GFP）融合蛋白定位于细胞核内。转激活和电泳迁移率变动分析（EMSA）进一步表明，ERF68 是一种功能性转录激活子，并与 GCC 框结合。此外，瞬时过表达 ERF68 导致番茄和烟草叶片出现自发病变，并增强了与 ET、SA、茉莉酸（JA）和过敏反应（HR）途径相关的基因的表达，而 ERF68 的沉默则增加了番茄对两种不亲和的黄单胞菌的敏感性。这些结果揭示了 ERF68 参与效应子触发的免疫（ETI）途径。为了鉴定 ERF68 的靶基因，进行了染色质免疫沉淀结合高通量测序（ChIP-seq）。在已确认的靶基因中，一些参与细胞死亡或疾病防御的基因受到 ERF68 的差异调控。我们的研究表明，ERF68 通过调节多种信号通路，正向调控过敏细胞死亡和疾病防御，为 ERFs 的复杂调控功能提供了重要的新信息。
