Elucidating the molecular basis of effector-triggered host susceptibility mediated by the TAL-like effector Brg11 from the bacterial pathogen Ralstonia solanacearum

阐明细菌病原体青枯菌中 TAL 样效应子 Brg11 介导的效应子触发宿主易感性的分子基础

• 批准号: 413908990
• 负责人: Professor Dr. Thomas Lahaye
• 金额: --
• 依托单位: Abteilung für Allgemeine Genetik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/413908990?language=en
• 关键词: Elucidating; molecular; basis; effector; triggered

Plant pathogens pose a permanent thread to global food security. To invade plants, phytopathogenic microbes rely on effector proteins that they inject into host cells to promote host susceptibility. Knowledge of effector targets inside host cells provides a possibility for knowledge-based breeding of pest-resistant crops. Thus, elucidation of the molecular basis of effector-triggered host susceptibility remains a major aim of fundamental and applied plant pathology.We study Ralstonia solanacearum a devastating bacterial pathogen that triggers bacterial wilt disease on numerous crop species. We have characterized Brg11, a R. solanacearum effector with high similarity to transcription activator-like effectors (TALEs) from the bacterial genus Xanthomonas. TALEs bind to effector binding elements (EBEs) present in host promoters and transcriptionally activate downstream host susceptibility (S) genes to promote disease. Given its relatedness to TALEs it’s conceivable that Brg11 promotes disease by transcriptional activation of host S genes. Thus, we aimed to identify host genes that are transcriptionally activated by Brg11 to clarify how it promotes disease.To identify Brg11 host target genes we determined a preferred target sequence of Brg11 (Brg11-EBE). A 18bp-motif resembling Brg11-EBE was identified upstream of all arginine decarboxylase (ADC) genes in R. solanacearum host genomes and accordingly this motif was designated as ADC-box. Combined analysis of RNA-Seq data and target site prediction suggests that ADC1 and ADC2 are the only direct target genes of Brg11 in tomato. Inspection of Brg11-induced versus intrinsic ADC transcripts revealed short (100 bps) and long (450 bps) 5’UTRs, respectively. Preliminary data suggest that differences in their 5’UTRs cause that translation of intrinsic but not Brg11-induced transcripts is feedback regulated by metabolites that accumulate due to activity of ADC enzymes. Thus, Brg11-induced ADC transcripts likely evade translational control mechanisms that limit translation from intrinsic transcripts. In summary, our findings suggest that R. solanacearum Brg11 promotes bacterial wilt disease by transcriptional activation of host ADC genes.In the framework of this proposal we aim to:- study translational regulation of intrinsic versus Brg11-induced ADC transcripts- establish a catalogue of metabolites that change as consequence of elevated ADC protein levels- Analyze growth-inhibiting/promoting activity of Brg11-induced metabolites on plant associated microbes- Establish cellular reporters to visualize Brg11 target cells and Brg11-induced changes- Investigate Brg11-induced changes at the transcriptional and translational levelIn summary, these studies shall provide insights into how Brg11-induced activation of ADC genes promotes bacterial wilt disease.

植物病原体对全球粮食安全构成了一条永久的线索。为了入侵植物，植物病原微生物依赖于它们注入宿主细胞的效应蛋白来促进宿主的敏感性。寄主细胞内效应靶标的了解为基于知识的抗虫作物育种提供了可能性。因此，阐明效应器触发寄主敏感性的分子基础仍然是基础和应用植物病理学的主要目标。我们研究了青枯病菌，它是一种毁灭性的细菌病原体，可以在许多作物上引发青枯病。我们已经鉴定了Brg11，它是青枯病菌的一个效应器，与细菌黄单胞菌属的转录激活器样效应器(TALE)有很高的相似性。TALS与宿主启动子中存在的效应器结合元件(EBE)结合，并在转录上激活下游宿主易感性(S)基因以促进疾病。考虑到它与故事的相关性，可以想象Brg11通过转录激活宿主S基因来促进疾病。因此，我们的目标是确定Brg11转录激活的宿主基因，以阐明它是如何促进疾病的。为了确定Brg11宿主靶基因，我们确定了Brg11的首选靶序列(Brg11-EBE)。在青枯菌寄主基因组的精氨酸脱羧酶(ADC)基因上游发现了一个与Brg11-EBE相似的18bp基序，命名为ADC-box。结合RNA-Seq数据分析和靶点预测，表明ADC1和ADC2是Brg11在番茄中仅有的直接靶基因。对Brg11诱导的ADC转录本与固有ADC转录本的比较显示，5‘UTRs分别较短(100bps)和较长(450bps)。初步数据表明，它们5‘UTRs的差异导致固有的而不是Brg11诱导的转录本的翻译是由ADC酶活性积累的代谢物反馈调节的。因此，Brg11诱导的ADC转录本可能逃避限制内在转录本翻译的翻译控制机制。综上所述，我们的发现表明青枯病菌Brg11通过转录激活宿主ADC基因促进青枯病的发生。在这一建议的框架内，我们的目标是：-研究内在ADC转录物与Brg11诱导的ADC转录物的翻译调控-建立ADC蛋白水平升高导致的代谢物目录-分析Brg11诱导的代谢物对植物相关微生物的生长抑制/促进活性-建立细胞记者以可视化Brg11靶细胞和Brg11诱导的变化-研究Brg11诱导的转录和翻译水平的变化。综上所述，这些研究将为Brg11诱导的ADC基因的激活如何促进青枯病提供洞察力。