Front Genet. 2015 Nov 24;6:336. doi: 10.3389/fgene.2015.00336. eCollection 2015.
An Individual-Based Diploid Model Predicts Limited Conditions Under Which Stochastic Gene Expression Becomes Advantageous.
Frontiers in genetics
Tomotaka Matsumoto, Katsuhiko Mineta, Naoki Osada, Hitoshi Araki
Affiliations
Affiliations
- Graduate School of Systems Life Sciences, Kyushu University Fukuoka, Japan ; Department of Population Genetics, National Institute of Genetics Mishima, Japan.
- Computational Bioscience Research Center (CBRC), King Abdullah University of Science and Technology (KAUST) Thuwal, Saudi Arabia.
- Department of Population Genetics, National Institute of Genetics Mishima, Japan ; Department of Genetics, SOKENDAI (The Graduate University for Advanced Studies) Mishima, Japan.
- Research Faculty of Agriculture, Hokkaido University Sapporo, Japan.
PMID: 26635872
PMCID: PMC4656826 DOI: 10.3389/fgene.2015.00336
Abstract
Recent studies suggest the existence of a stochasticity in gene expression (SGE) in many organisms, and its non-negligible effect on their phenotype and fitness. To date, however, how SGE affects the key parameters of population genetics are not well understood. SGE can increase the phenotypic variation and act as a load for individuals, if they are at the adaptive optimum in a stable environment. On the other hand, part of the phenotypic variation caused by SGE might become advantageous if individuals at the adaptive optimum become genetically less-adaptive, for example due to an environmental change. Furthermore, SGE of unimportant genes might have little or no fitness consequences. Thus, SGE can be advantageous, disadvantageous, or selectively neutral depending on its context. In addition, there might be a genetic basis that regulates magnitude of SGE, which is often referred to as "modifier genes," but little is known about the conditions under which such an SGE-modifier gene evolves. In the present study, we conducted individual-based computer simulations to examine these conditions in a diploid model. In the simulations, we considered a single locus that determines organismal fitness for simplicity, and that SGE on the locus creates fitness variation in a stochastic manner. We also considered another locus that modifies the magnitude of SGE. Our results suggested that SGE was always deleterious in stable environments and increased the fixation probability of deleterious mutations in this model. Even under frequently changing environmental conditions, only very strong natural selection made SGE adaptive. These results suggest that the evolution of SGE-modifier genes requires strict balance among the strength of natural selection, magnitude of SGE, and frequency of environmental changes. However, the degree of dominance affected the condition under which SGE becomes advantageous, indicating a better opportunity for the evolution of SGE in different genetic models.
Keywords: effective population size; environmental change; individual-based simulation; stochastic gene expression; viability selection
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