Phenotypic plasticity can facilitate adaptive evolution in gene regulatory circuits
1 University of Zurich, Dept. of Biochemistry, Bldg. Y27 Winterthurerstrasse 190 CH-8057 Zurich, Switzerland
2 The Swiss Institute of Bioinformatics. Quartier Sorge, Batiment Genopode, 1015 Lausanne, Switzerland
3 INRA, UMR 0320/UMR 8120 Génétique Végétale, F-91190 Gif-sur- Yvette, France
4 The Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA
BMC Evolutionary Biology 2011, 11:5 doi:10.1186/1471-2148-11-5Published: 6 January 2011
Many important evolutionary adaptations originate in the modification of gene regulatory circuits to produce new gene activity phenotypes. How do evolving populations sift through an astronomical number of circuits to find circuits with new adaptive phenotypes? The answer may often involve phenotypic plasticity. Phenotypic plasticity allows a genotype to produce different - alternative - phenotypes after non-genetic perturbations that include gene expression noise, environmental change, or epigenetic modification.
We here analyze a well-studied model of gene regulatory circuits. A circuit's genotype encodes the regulatory interactions among circuit genes, and its phenotype corresponds to a stable gene activity pattern the circuit forms. For this model, we study how genotypes are arranged in genotype space, where the distance between two genotypes reflects the number of regulatory mutations that set those genotypes apart. Specifically, we address whether this arrangement favors adaptive evolution mediated by plasticity. We find that plasticity facilitates the origin of genotypes that produce a new phenotype in response to non-genetic perturbations. We also find that selection can then stabilize the new phenotype genetically, allowing it to become a circuit's dominant gene expression phenotype. These are generic properties of the circuits we study here.
Taken together, our observations suggest that phenotypic plasticity frequently facilitates the evolution of novel beneficial gene activity patterns in gene regulatory circuits.