title: Inherent characteristics of gene expression for buffering environmental changes without the corresponding transcriptional regulations.
abstract: Gene expression patterning is crucial for environmental nutritional responses such as the nitrogen response inEscherichia coli. The nitrogen response is primarily regulated by the expression of glutamine synthetase (GS), which catalyzes the sole reaction of glutamine formation, by cis-logic regulatory circuits. Here, by removing the entire corresponding operator and promoter regions required for the control of GS, we constructed anE. colistrain that enables the detection of the basal GS gene expression, which is expressed from a plain promoter unrelated to the nitrogen response, and measured by co-transcribed GFP expression, an indicator of GS expression. Using strain cultures, we found that the GS expression level was able to shift inversely against the change of the environmental glutamine concentration. As a control experiment, we repeated similar experiments with another strain in which the GS regulatory region remained intact and the GFP gene following the plain promoter was introduced into a different chromosomal site. For this strain, we found that the GFP expression level did not shift in accordance with the environmental glutamine concentration. These results showed that GS expression from the plain promoter exhibited a responsive ability to buffer environmental changes, whereas the GS expression shift did not correlate with the specific characteristics of the plain promoter and GFP expression. This study identifies the inherent characteristics of basal gene expression in response to environmental changes, facilitating a deeper understanding of cellular design principles.
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Department of Bioinformatics Engineering, Graduate School of Information Science and Technology, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Kashiwagi
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Itaru
authors.initials: I
authors.lastname: Urabe
authors.affiliation: Department of Bioinformatics Engineering, Graduate School of Information Science and Technology, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan; Complex Systems Biology Project, ERATO, JST, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yomo
keywords: Escherichia coli; glutamine synthetase; nitrogen response; operator-deleted gene expression; robust phenomena