State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
Mol Microbiol. 2011 Oct;82(1):236-50. doi: 10.1111/j.1365-2958.2011.07811.x. Epub 2011 Sep 14.
In streptomycetes, a quorum-sensing mechanism mediated by γ-butyrolactones (GBLs) and their cognate receptors was known to trigger secondary metabolism and morphological differentiation. However, many aspects on the control of GBL signal production are not understood. In this work, we report that ScbR2, the pseudo GBL receptor in Streptomyces coelicolor, negatively controls the biosynthesis of γ-butyrolactone (SCB1) by directly repressing the transcription of scbA, which encodes the key enzyme for SCB1 biosynthesis. Similarly, the pseudo GBL receptor JadR2 in Streptomyces venezuelae was shown to repress the expression of jadW1, which also encodes the putative GBL synthase. These regulatory relationships were verified in Escherichia coli using lux-based reporter constructs. Additionally, the temporal expression profiles of scbA, scbR2 and scbR (receptor gene for SCB1) were examined in Streptomyces coelicolor, which showed the sequential expression of ScbR/R2 regulators in the control of SCB1 production. Overall, our results clearly demonstrated that pseudo GBL receptors play a novel role in controlling GBL biosynthesis in streptomycetes. As ScbR/R2 homologues and their binding sites upstream of GBL synthase genes are commonly found in Streptomyces species, and ScbR2 homologues cross-recognize each other's target promoters, the ScbA/R/R2 quorum-sensing regulatory system appears to represent an evolutionarily conserved signal control mechanism.
在链霉菌中，一种由 γ-丁内酯 (GBL) 及其同源受体介导的群体感应机制被认为能触发次级代谢和形态分化。然而，GBL 信号产生的控制的许多方面尚不清楚。在这项工作中，我们报告了链霉菌灰色链霉菌中的伪 GBL 受体 ScbR2 通过直接抑制 γ-丁内酯 (SCB1) 生物合成的关键酶 scbA 的转录来负调控 GBL 信号的产生。类似地，链霉菌委内瑞拉链霉菌中的伪 GBL 受体 JadR2 被证明可以抑制 jadW1 的表达，jadW1 编码推测的 GBL 合酶。这些调控关系在大肠杆菌中使用 lux 报告基因构建得到了验证。此外，我们还检测了链霉菌灰色链霉菌中 scbA、scbR2 和 scbR（SCB1 受体基因）的时空表达谱，结果表明 ScbR/R2 调控因子在 SCB1 产生的控制中表现出顺序表达。总的来说，我们的研究结果清楚地表明，伪 GBL 受体在链霉菌的 GBL 生物合成调控中发挥了新的作用。由于 ScbR/R2 同源物及其在 GBL 合酶基因上游的结合位点在链霉菌属中普遍存在，并且 ScbR2 同源物相互识别彼此的靶启动子，因此 ScbA/R/R2 群体感应调控系统似乎代表了一种进化保守的信号调控机制。
