Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Nanjing, People's Republic of China.
College of Plant Protection, Nanjing Agricultural University, Nanjing, People's Republic of China.
Appl Environ Microbiol. 2018 Jan 17;84(3). doi: 10.1128/AEM.01754-17. Print 2018 Feb 1.
is a Gram-negative, environmentally ubiquitous bacterium that produces a secondary metabolite, called heat-stable antifungal factor (HSAF), as an antifungal factor against plant and animal fungal pathogens. 4-Hydroxybenzoic acid (4-HBA) is a newly identified diffusible factor that regulates HSAF synthesis via LysR (LysR), an LysR-type transcription factor (TF). Here, to identify additional TFs within the 4-HBA regulatory pathway that control HSAF production, we reanalyzed the LenB2-based transcriptomic data, in which LenB2 is the enzyme responsible for 4-HBA production. This survey led to identification of three TFs (Le4806, Le4969, and Le3904). Of them, LarR (Le4806), a member of the MarR family proteins, was identified as a new TF that participated in the 4-HBA-dependent regulation of HSAF production. Our data show the following: (i) that LarR is a downstream component of the 4-HBA regulatory pathway controlling the HSAF level, while LysR is the receptor of 4-HBA; (ii) that 4-HBA and LysR have opposite regulatory effects on transcription whereby transcript is negatively modulated by 4-HBA while LysR, in contrast, exerts positive transcriptional regulation by directly binding to the promoter without being affected by 4-HBA ; (iii) that LarR, similar to LysR, can bind to the promoter of the HSAF biosynthetic gene operon, leading to positive regulation of HSAF production; and (iv) that LarR and LysR cannot interact and instead control HSAF biosynthesis independently. These results outline a previously uncharacterized mechanism by which biosynthesis of the antibiotic HSAF in is modulated by the interplay of 4-HBA, a diffusible molecule, and two different TFs. Bacteria use diverse chemical signaling molecules to regulate a wide range of physiological and cellular processes. 4-HBA is an "old" chemical molecule that is produced by diverse bacterial species, but its regulatory function and working mechanism remain largely unknown. We previously found that 4-HBA in could serve as a diffusible factor regulating HSAF synthesis via LysR Here, we further identified LarR, an MarR family protein, as a second TF that participates in the 4-HBA-dependent regulation of HSAF biosynthesis. Our results dissected how LarR acts as a protein linker to connect 4-HBA and HSAF synthesis, whereby LarR also has cross talk with LysR Thus, our findings not only provide fundamental insight regarding how a diffusible molecule (4-HBA) adopts two different types of TFs for coordinating HSAF biosynthesis but also show the use of applied microbiology to increase the yield of the antibiotic HSAF by modification of the 4-HBA regulatory pathway in .
是一种革兰氏阴性、环境无处不在的细菌，它产生一种次级代谢产物，称为热稳定抗真菌因子（HSAF），作为一种抗真菌因子对抗植物和动物真菌病原体。4-羟基苯甲酸（4-HBA）是一种新鉴定的可扩散因子，通过 LysR（LysR）调节 HSAF 合成，LysR 是一种 LysR 型转录因子（TF）。在这里，为了鉴定控制 HSAF 产生的 4-HBA 调节途径中的其他 TF，我们重新分析了基于 LenB2 的转录组数据，其中 LenB2 是负责 4-HBA 产生的酶。这项调查导致了三个 TF（Le4806、Le4969 和 Le3904）的鉴定。其中，LarR（Le4806），MarR 家族蛋白的成员，被鉴定为参与 4-HBA 依赖调节 HSAF 产生的新 TF。我们的数据表明：（i）LarR 是控制 HSAF 水平的 4-HBA 调节途径的下游成分，而 LysR 是 4-HBA 的受体；（ii）4-HBA 和 LysR 对转录具有相反的调节作用，即 转录物受 4-HBA 负调控，而 LysR 相反，通过直接结合 启动子而不被 4-HBA 影响，正向转录调节；（iii）LarR 与 LysR 相似，可以结合 HSAF 生物合成基因操纵子的启动子，从而正向调节 HSAF 的产生；（iv）LarR 和 LysR 不能相互作用，而是独立控制 HSAF 生物合成。这些结果概述了一种以前未被描述的机制，即 通过 4-HBA 这种可扩散分子和两种不同的 TF 的相互作用来调节 的抗生素 HSAF 的生物合成。细菌利用多种化学信号分子来调节广泛的生理和细胞过程。4-HBA 是一种“旧”化学分子，由多种细菌产生，但它的调节功能和工作机制在很大程度上仍然未知。我们之前发现， 中的 4-HBA 可以作为一种可扩散因子，通过 LysR 调节 HSAF 合成。在这里，我们进一步鉴定了 LarR，一种 MarR 家族蛋白，作为参与 4-HBA 依赖的 HSAF 生物合成调节的第二个 TF。我们的结果剖析了 LarR 如何作为一种蛋白质连接子来连接 4-HBA 和 HSAF 合成，其中 LarR 还与 LysR 进行了交叉对话。因此，我们的发现不仅提供了关于可扩散分子（4-HBA）如何采用两种不同类型的 TF 来协调 HSAF 生物合成的基本见解，而且还展示了如何利用应用微生物学通过修饰 4-HBA 调节途径来增加抗生素 HSAF 的产量。
