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Inherent characteristics of gene expression for buffering environmental changes without the corresponding transcriptional regulations

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ABSTRACT

Gene expression patterning is crucial for environmental nutritional responses such as the nitrogen response in Escherichia 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 an E. coli strain 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.

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Related in: MedlinePlus

Acclimation of cells by serial-transfer cultures to culture conditions used to start environmental glutamine transition experiments. Specific growth rates of cells were traced at each subculture. E. coli strain OSU8 was separately grown at 37°C on medium D with 5 mM glutamine or without glutamine (i.e., 0 mM glutamine) until a plateau level of the specific growth rate of cells was reached.
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f2-2_63: Acclimation of cells by serial-transfer cultures to culture conditions used to start environmental glutamine transition experiments. Specific growth rates of cells were traced at each subculture. E. coli strain OSU8 was separately grown at 37°C on medium D with 5 mM glutamine or without glutamine (i.e., 0 mM glutamine) until a plateau level of the specific growth rate of cells was reached.

Mentions: To acclimate cells to culture conditions, the E. coli strain OSU8 was cultured with serial-transfer (see Materials and Methods) under the culture conditions used to start the environmental glutamine transition experiments. Assuming logarithmic cell growth, the specific growth rate was calculated for each subculture (see Materials and Methods). As the acclimation proceeded, the specific growth rate increased and finally reached a plateau level characteristic of the strain and culture conditions (Fig. 2). We confirmed mutation absence when sequencing the PtetA promoter and gfp gene in each of the three colonies that formed the final serial-transfer culture of the two lines grown on medium D with or without 5 mM glutamine.


Inherent characteristics of gene expression for buffering environmental changes without the corresponding transcriptional regulations
Acclimation of cells by serial-transfer cultures to culture conditions used to start environmental glutamine transition experiments. Specific growth rates of cells were traced at each subculture. E. coli strain OSU8 was separately grown at 37°C on medium D with 5 mM glutamine or without glutamine (i.e., 0 mM glutamine) until a plateau level of the specific growth rate of cells was reached.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5036647&req=5

f2-2_63: Acclimation of cells by serial-transfer cultures to culture conditions used to start environmental glutamine transition experiments. Specific growth rates of cells were traced at each subculture. E. coli strain OSU8 was separately grown at 37°C on medium D with 5 mM glutamine or without glutamine (i.e., 0 mM glutamine) until a plateau level of the specific growth rate of cells was reached.
Mentions: To acclimate cells to culture conditions, the E. coli strain OSU8 was cultured with serial-transfer (see Materials and Methods) under the culture conditions used to start the environmental glutamine transition experiments. Assuming logarithmic cell growth, the specific growth rate was calculated for each subculture (see Materials and Methods). As the acclimation proceeded, the specific growth rate increased and finally reached a plateau level characteristic of the strain and culture conditions (Fig. 2). We confirmed mutation absence when sequencing the PtetA promoter and gfp gene in each of the three colonies that formed the final serial-transfer culture of the two lines grown on medium D with or without 5 mM glutamine.

View Article: PubMed Central - PubMed

ABSTRACT

Gene expression patterning is crucial for environmental nutritional responses such as the nitrogen response in Escherichia 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 an E. coli strain 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.

No MeSH data available.


Related in: MedlinePlus