With the development of engineering the microbial cell factories, biosensors have been used widely for regulation of cellular metabolism and high-throughput screening. However, most of the biosensors constructed in Saccharomyces cerevisiae are designed for transcriptional activation. Very few studies have dedicated to the development of genetic circuit for repressive regulation, which is also indispensable for the dynamic control of metabolism. In this study, through transcriptional deactivation design, we developed transcription-factor-based biosensors to allow repressive regulation in response to ligand. Using a malonyl-CoA sensing system as an example, the biosensor was constructed and systematically engineered to optimize the dynamic range by comparing transcriptional activity of the activators, evaluating the positions and numbers of the operators in the promoter and comparing the effects of different promoters. A biosensor with 82% repression ratio was obtained. Based on this design principle, another two biosensors, which sense acyl-CoA or xylose and downregulate gene expression, were also successfully constructed. Our work systematically optimized the biosensors for repressive regulation in yeast for the first time. It provided useful framework to construct similar biosensors. Combining the widely reported biosensors for transcriptional activation with the biosensors developed here, it is now possible to construct biosensors with opposing transcriptional activities in yeast.

中文翻译：

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工程化基于转录因子的生物传感器，用于通过酿酒酵母中的转录失活设计进行抑制性调控。

随着微生物细胞工厂工程的发展，生物传感器已被广泛用于调节细胞代谢和高通量筛选。但是，在酿酒酵母中构建的大多数生物传感器都是为转录激活而设计的。很少有研究致力于抑制性调节的遗传回路的开发，这对于代谢的动态控制也是必不可少的。在这项研究中，通过转录失活设计，我们开发了基于转录因子的生物传感器，以允许对配体的阻抑调节。以丙二酰辅酶A感测系统为例，构建了生物传感器并对其进行了系统地工程设计，以通过比较激活剂的转录活性来优化动态范围，评估启动子中操纵子的位置和数目，并比较不同启动子的作用。获得了具有82％阻抑率的生物传感器。根据该设计原理，还成功构建了另外两个生物传感器，它们可感知酰基辅酶A或木糖并下调基因表达。我们的工作首次系统地优化了生物传感器，用于酵母中的阻抑性调控。它为构建类似的生物传感器提供了有用的框架。将广泛报道的用于转录激活的生物传感器与此处开发的生物传感器相结合，现在有可能在酵母中构建具有相反转录活性的生物传感器。还成功地构建了另外两个生物传感器，它们可感知酰基辅酶A或木糖并下调基因表达。我们的工作首次系统地优化了生物传感器，用于酵母中的阻抑性调控。它为构建类似的生物传感器提供了有用的框架。将广泛报道的用于转录激活的生物传感器与此处开发的生物传感器相结合，现在有可能在酵母中构建具有相反转录活性的生物传感器。还成功地构建了另外两个生物传感器，它们可感知酰基辅酶A或木糖并下调基因表达。我们的工作首次系统地优化了生物传感器，用于酵母中的阻抑调节。它为构建类似的生物传感器提供了有用的框架。将广泛报道的用于转录激活的生物传感器与此处开发的生物传感器相结合，现在可以构建酵母中具有相反转录活性的生物传感器。