The TyrR transcription factor controls the expression of genes for the uptake and biosynthesis of aromatic amino acids in Escherichia coli. In the plant-associated and clinically significant proteobacterium Enterobacter ludwigii UW5, the TyrR orthologue was previously shown to regulate genes that encode enzymes for synthesis of the plant hormone indole-3-acetic acid and for gluconeogenesis, indicating a broader function for the transcription factor. This study aimed to delineate the TyrR regulon of E. ludwigii by comparing the transcriptomes of the wild type and a tyrR deletion strain. In E. ludwigii, TyrR positively or negatively regulates the expression of over 150 genes. TyrR downregulated expression of envelope stress response regulators CpxR and CpxP through interaction with a DNA binding site in the intergenic region between divergently transcribed cpxP and cpxR. Repression of cpxP was alleviated by tyrosine. Methyltransferase gene dmpM, which is possibly involved in antibiotic synthesis, was strongly activated in the presence of tyrosine and phenylalanine by TyrR binding to its promoter region. TyrR also regulated expression of genes for aromatic catabolism and anaerobic respiration. Our findings suggest that the E. ludwigii TyrR regulon has diverged from that of E. coli to include genes for survival in the diverse environments that this bacterium inhabits and illustrate the expansion and plasticity of transcription factor regulons.

中文翻译：

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路德维希根杆菌 UW5 中 TyrR 调节子的表征揭示了与 CpxR 包膜应激反应的重叠

TyrR 转录因子控制大肠杆菌中芳香族氨基酸的摄取和生物合成基因的表达。在与植物相关且具有临床意义的变形菌路德维希肠杆菌UW5 中，TyrR 直系同源物先前被证明可以调节编码植物激素吲哚-3-乙酸合成和糖异生的酶的基因，表明转录因子具有更广泛的功能。本研究旨在通过比较野生型和TyrR缺失菌株的转录组来描述路德维希大肠杆菌的 TyrR 调节子。在路德维氏球菌中，TyrR 正向或负向调节超过 150 个基因的表达。TyrR 通过与不同转录的 cpxP 和 cpxR 之间基因间区域的 DNA 结合位点相互作用，下调包膜应激反应调节因子CpxR和CpxP的表达。酪氨酸减轻了cpxP的抑制。甲基转移酶基因dmpM可能参与抗生素合成，在酪氨酸和苯丙氨酸存在的情况下，TyrR 与其启动子区域结合而被强烈激活。TyrR 还调节芳香分解代谢和无氧呼吸基因的表达。我们的研究结果表明，路德维希大肠杆菌TyrR 调节子与大肠杆菌的调节子不同，它包含在该细菌栖息的不同环境中生存的基因，并说明了转录因子调节子的扩展和可塑性。