scholarly journals Empirical noise-mean fitness landscapes and the evolution of gene expression

2018 ◽  
Author(s):  
Joern M Schmiedel ◽  
Lucas B. Carey ◽  
Ben Lehner
Keyword(s):  
Gene Expression ◽  
Fitness Landscape ◽  
Fitness Landscapes ◽  
Similar Magnitude ◽  
Expression Systems ◽  
Fitness Effects ◽  
Mean Fitness ◽  
Noise In Gene Expression ◽  
Cell Variation ◽  
Magnitude Sensitivity

The effects of cell-to-cell variation (noise) in gene expression have proven difficult to quantify, in part due to the mechanistic coupling of noise to mean expression. To independently evaluate the effects of changes in expression mean and noise we determined the fitness landscapes in mean-noise expression space for 33 genes in yeast. The landscapes can be decomposed into two principal topologies: the fitness effects of protein shortage and surplus. For most genes, the fitness impact of sustained (mean) and short-lived (noise) deviations away from the expression optimum are linked and of similar magnitude. Sensitivity to both protein shortage and surplus creates a fitness landscape in which an epistatic ratchet uncouples the evolution of noise from mean expression, promoting noise minimization. These results demonstrate that noise is detrimental for many genes and reveal non-trivial consequences of mean-noise-fitness topologies for the evolution of gene expression systems.

scholarly journals Plasmids for Independently Tunable, Low-Noise Expression of Two Genes

mSphere ◽  
2019 ◽  
Vol 4 (3) ◽  
Author(s):  
João P. N. Silva ◽  
Soraia Vidigal Lopes ◽  
Diogo J. Grilo ◽  
Zach Hensel
Keyword(s):  
Gene Expression ◽  
Protein Expression ◽  
Low Noise ◽  
Expression Systems ◽  
Extrinsic Noise ◽  
Gene Expression Noise ◽  
Expression Noise ◽  
Foreign Proteins ◽  
Noise Limit ◽  
Cell Variation

ABSTRACTSome microbiology experiments and biotechnology applications can be improved if it is possible to tune the expression of two different genes at the same time with cell-to-cell variation at or below the level of genes constitutively expressed from the chromosome (the “extrinsic noise limit”). This was recently achieved for a single gene by exploiting negative autoregulation by the tetracycline repressor (TetR) and bicistronic gene expression to reduce gene expression noise. We report new plasmids that use the same principles to achieve simultaneous, low-noise expression for two genes inEscherichia coli. The TetR system was moved to a compatible plasmid backbone, and a system based on thelacrepressor (LacI) was found to also exhibit gene expression noise below the extrinsic noise limit. We characterized gene expression mean and noise across the range of induction levels for these plasmids, applied the LacI system to tune expression for single-molecule mRNA detection under two different growth conditions, and showed that two plasmids can be cotransformed to independently tune expression of two different genes.IMPORTANCEMicrobiologists often express foreign proteins in bacteria in order study them or to use bacteria as a microbial factory. Usually, this requires controlling the number of foreign proteins expressed in each cell, but for many common protein expression systems, it is difficult to “tune” protein expression without large cell-to-cell variation in expression levels (called “noise” in protein expression). This work describes two protein expression systems that can be combined in the same cell, with tunable expression levels and very low protein expression noise. One new system was used to detect single mRNA molecules by fluorescence microscopy, and the two systems were shown to be independent of each other. These protein expression systems may be useful in any experiment or biotechnology application that can be improved with low protein expression noise.

scholarly journals Hsf1 phosphorylation generates cell-to-cell variation in Hsp90 levels and promotes phenotypic plasticity

2017 ◽  
Author(s):  
Xu Zheng ◽  
Ali Beyzavi ◽  
Joanna Krakowiak ◽  
Nikit Patel ◽  
Ahmad S. Khalil ◽  
...  
Keyword(s):  
Gene Expression ◽  
Phenotypic Plasticity ◽  
Important Determinant ◽  
Phenotypic Diversity ◽  
Yeast Cells ◽  
Wide Range ◽  
Differential Tuning ◽  
Gene Expression Heterogeneity ◽  
Noise In Gene Expression ◽  
Cell Variation

ABSTRACTClonal populations of cells exhibit cell-to-cell variation in the transcription of individual genes. In addition to this “noise” in gene expression, heterogeneity in the proteome and the proteostasis network expands the phenotypic diversity of a population. Heat shock transcription factor (Hsf1) regulates chaperone gene expression, thereby coupling transcriptional noise to proteostasis. Here we show that cell-to-cell variation in Hsf1 activity is an important determinant of phenotypic plasticity. Budding yeast cells with high Hsf1 activity were enriched for the ability to acquire resistance to an antifungal drug, and this enrichment depended on Hsp90 – a known “phenotypic capacitor” and canonical Hsf1 target. We show that Hsf1 phosphorylation promotes cell-to-cell variation, and this variation – rather than absolute Hsf1 activity – promotes antifungal resistance. We propose that Hsf1 phosphorylation enables differential tuning of the proteostasis network in individual cells, allowing populations to access a wide range of phenotypic states.

scholarly journals The fitness landscape of the codon space across environments

2018 ◽  
Author(s):  
Inès Fragata ◽  
Sebastian Matuszewski ◽  
Mark A. Schmitz ◽  
Thomas Bataillon ◽  
Jeffrey D. Jensen ◽  
...  
Keyword(s):  
Amino Acid ◽  
Evolutionary Dynamics ◽  
Fitness Landscape ◽  
Fitness Landscapes ◽  
Synonymous Mutations ◽  
Landscape Studies ◽  
Fitness Effects ◽  
Bayesian Monte Carlo ◽  
The Relationship

AbstractFitness landscapes map the relationship between genotypes and fitness. However, most fitness landscape studies ignore the genetic architecture imposed by the codon table and thereby neglect the potential role of synonymous mutations. To quantify the fitness effects of synonymous mutations and their potential impact on adaptation on a fitness landscape, we use a new software based on Bayesian Monte Carlo Markov Chain methods and reestimate selection coefficients of all possible codon mutations across 9 amino-acid positions in Saccharomyces cerevisiae Hsp90 across 6 environments. We quantify the distribution of fitness effects of synonymous mutations and show that it is dominated by many mutations of small or no effect and few mutations of larger effect. We then compare the shape of the codon fitness landscape across amino-acid positions and environments, and quantify how the consideration of synonymous fitness effects changes the evolutionary dynamics on these fitness landscapes. Together these results highlight a possible role of synonymous mutations in adaptation and indicate the potential mis-inference when they are neglected in fitness landscape studies.

scholarly journals On the (un)predictability of a large intragenic fitness landscape

2016 ◽  
Vol 113 (49) ◽  
pp. 14085-14090 ◽  
Author(s):  
Claudia Bank ◽  
Sebastian Matuszewski ◽  
Ryan T. Hietpas ◽  
Jeffrey D. Jensen
Keyword(s):  
Amino Acid ◽  
Fitness Landscape ◽  
Fitness Landscapes ◽  
Fitness Effects ◽  
Elevated Salinity ◽  
Theoretical Predictions ◽  
Experimental Approaches ◽  
Next Generation Sequencing Ngs ◽  
Negative Epistasis ◽  
Generation Sequencing

The study of fitness landscapes, which aims at mapping genotypes to fitness, is receiving ever-increasing attention. Novel experimental approaches combined with next-generation sequencing (NGS) methods enable accurate and extensive studies of the fitness effects of mutations, allowing us to test theoretical predictions and improve our understanding of the shape of the true underlying fitness landscape and its implications for the predictability and repeatability of evolution. Here, we present a uniquely large multiallelic fitness landscape comprising 640 engineered mutants that represent all possible combinations of 13 amino acid-changing mutations at 6 sites in the heat-shock protein Hsp90 in Saccharomyces cerevisiae under elevated salinity. Despite a prevalent pattern of negative epistasis in the landscape, we find that the global fitness peak is reached via four positively epistatic mutations. Combining traditional and extending recently proposed theoretical and statistical approaches, we quantify features of the global multiallelic fitness landscape. Using subsets of the data, we demonstrate that extrapolation beyond a known part of the landscape is difficult owing to both local ruggedness and amino acid-specific epistatic hotspots and that inference is additionally confounded by the nonrandom choice of mutations for experimental fitness landscapes.

scholarly journals On the way toward regulatable expression systems in acetic acid bacteria: target gene expression and use cases

2021 ◽  
Author(s):  
Philipp Moritz Fricke ◽  
Angelika Klemm ◽  
Michael Bott ◽  
Tino Polen
Keyword(s):  
Gene Expression ◽  
Acetic Acid ◽  
Literature Search ◽  
Target Gene ◽  
Target Genes ◽  
Recombinant Dna ◽  
Acetic Acid Bacteria ◽  
Homoserine Lactone ◽  
Expression Systems ◽  
Target Gene Expression

Abstract Acetic acid bacteria (AAB) are valuable biocatalysts for which there is growing interest in understanding their basics including physiology and biochemistry. This is accompanied by growing demands for metabolic engineering of AAB to take advantage of their properties and to improve their biomanufacturing efficiencies. Controlled expression of target genes is key to fundamental and applied microbiological research. In order to get an overview of expression systems and their applications in AAB, we carried out a comprehensive literature search using the Web of Science Core Collection database. The Acetobacteraceae family currently comprises 49 genera. We found overall 6097 publications related to one or more AAB genera since 1973, when the first successful recombinant DNA experiments in Escherichia coli have been published. The use of plasmids in AAB began in 1985 and till today was reported for only nine out of the 49 AAB genera currently described. We found at least five major expression plasmid lineages and a multitude of further expression plasmids, almost all enabling only constitutive target gene expression. Only recently, two regulatable expression systems became available for AAB, an N-acyl homoserine lactone (AHL)-inducible system for Komagataeibacter rhaeticus and an l-arabinose-inducible system for Gluconobacter oxydans. Thus, after 35 years of constitutive target gene expression in AAB, we now have the first regulatable expression systems for AAB in hand and further regulatable expression systems for AAB can be expected. Key points • Literature search revealed developments and usage of expression systems in AAB. • Only recently 2 regulatable plasmid systems became available for only 2 AAB genera. • Further regulatable expression systems for AAB are in sight.

scholarly journals Probing the effect of promoters on noise in gene expression using thousands of designed sequences

2014 ◽  
Vol 24 (10) ◽  
pp. 1698-1706 ◽  
Author(s):  
Eilon Sharon ◽  
David van Dijk ◽  
Yael Kalma ◽  
Leeat Keren ◽  
Ohad Manor ◽  
...  
Keyword(s):  
Gene Expression ◽  
Noise In Gene Expression

Construction of gene expression systems in insect cell lines using promoters from the silkworm, Bombyx mori

2008 ◽  
Vol 133 (1) ◽  
pp. 9-17 ◽  
Author(s):  
Jae Man Lee ◽  
Masateru Takahashi ◽  
Hiroaki Mon ◽  
Hitoshi Mitsunobu ◽  
Katsumi Koga ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bombyx Mori ◽  
Cell Lines ◽  
Insect Cell ◽  
Expression Systems ◽  
Insect Cell Lines ◽  
Silkworm Bombyx Mori

scholarly journals UGA Read-Through Artifacts—When Popular Gene Expression Systems Need a pATCH

BioTechniques ◽  
1998 ◽  
Vol 24 (5) ◽  
pp. 789-794 ◽  
Author(s):  
Gavin MacBeath ◽  
Peter Kast
Keyword(s):  
Gene Expression ◽  
Expression Systems
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