title: Genetic and environmental factors affecting cryptic variations in gene regulatory networks.
abstract: BACKGROUND
  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. 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.
  
  
  RESULTS
  Populations 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.
  
  
  CONCLUSIONS
  Given 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.
authors.affiliation: Department of Ecology and Evolution, Graduate School of Life Sciences, Tohoku University, Sendai 980-8578, Japan. heavy.watal@gmail.com
authors.forename: Watal M
authors.initials: WM
authors.lastname: Iwasaki
authors.forename: Masaki E
authors.initials: ME
authors.lastname: Tsuda
authors.forename: Masakado
authors.initials: M
authors.lastname: Kawata
mesh_terms: D000064:Acclimatization / Q000235:genetics; D000222:Adaptation, Physiological / Q000235:genetics; D004777:Environment; D019143:Evolution, Molecular; D053263:Gene Regulatory Networks; D014644:Genetic Variation; D005828:Genetics, Population; D006801:Humans; D010641:Phenotype; D012641:Selection, Genetic