Genetic and environmental factors affecting cryptic variations in gene regulatory networks.

Watal M Iwasaki,Masakado Kawata,Masaki E Tsuda

doi:10.1186/1471-2148-13-91

Watal M Iwasaki, Masakado Kawata + Show 1 more

Open Access

https://doi.org/10.1186/1471-2148-13-91

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Abstract

BackgroundCryptic genetic variation (CGV) is considered to facilitate phenotypic evolution by producing visible variations in response to changes in the internal and/or external environment. Several mechanisms enabling the accumulation and release of CGVs have been proposed. In this study, we focused on gene regulatory networks (GRNs) as an important mechanism for producing CGVs, and examined how interactions between GRNs and the environment influence the number of CGVs by using individual-based simulations.ResultsPopulations of GRNs were allowed to evolve under various stabilizing selections, and we then measured the number of genetic and phenotypic variations that had arisen. Our results showed that CGVs were not depleted irrespective of the strength of the stabilizing selection for each phenotype, whereas the visible fraction of genetic variation in a population decreased with increasing strength of selection. On the other hand, increasing the number of different environments that individuals encountered within their lifetime (i.e., entailing plastic responses to multiple environments) suppressed the accumulation of CGVs, whereas the GRNs with more genes and interactions were favored in such heterogeneous environments.ConclusionsGiven the findings that the number of CGVs in a population was largely determined by the size (order) of GRNs, we propose that expansion of GRNs and adaptation to novel environments are mutually facilitating and sustainable sources of evolvability and hence the origins of biological diversity and complexity.

Highlights

Cryptic genetic variation (CGV) is considered to facilitate phenotypic evolution by producing visible variations in response to changes in the internal and/or external environment
Cryptic variations in Gene regulatory network (GRN) In the default parameter set (Table 1), significantly more phenotypic variations appeared in response to a novel environmental change (Pnovel) compared with variations observed under the normal condition (Pnormal) during stabilizing selection over 20,000 generations (Figure 3; V = 5825, P = 4.298 × 10−14)
Phenotypic differences were caused by at least one genetic difference in the GRNs; the phenotypic variations were partly due to the total genetic variation

Summary

Introduction

Cryptic genetic variation (CGV) is considered to facilitate phenotypic evolution by producing visible variations in response to changes in the internal and/or external environment. Understanding how biological populations generate and maintain genetic variations that contribute to phenotypic variations is one of the most important issues in evolutionary biology. The molecular chaperone called HSP90 is a wellknown example of such a mechanism [13,14]. It neutralizes non-synonymous substitutions on DNA sequences by assisting the proper folding of polypeptide chains. Apart form the mechanisms involving a molecular chaperone, redundancy and modularity produce robustness in organisms [18]

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