02.07.2020: Most animal and plant traits are polygenic, meaning they are encoded by more than one gene, as genome-wide association studies (GWAS) have shown. A scientific concept to describe the genetic basis of the adaption processes is still lacking, however. In a recently published study in Nature Reviews Genetics, researchers from Vetmeduni Vienna now introduce just such a concept: adaptive architecture.

Quantitative genetics, which has its roots in animal and plant breeding, is becoming increasingly important as a field of research. Molecular mapping, for example, has shown that many genes are not only involved in traits that are relevant to breeding but also play a role in many human diseases. Despite the explosive growth of genomic data in the recent past, however, a uniform framework describing the dynamics of gene variants involved in adaptation processes – triggered, for example, by environmental changes such as global warming – has been lacking.

Extension of previous models of genetic architecture

Building on recent theoretical and empirical work, the researchers – Neda Barghi and Christian Schlötterer from the Institute of Population Genetics at Vetmeduni Vienna and Joachim Hermisson from Max Perutz Labs and the Faculty of Mathematics at the University of Vienna – introduce the newly developed concept of adaptive architecture. This model extends the genetic architecture of an adaptive trait by including factors that influence its adaptive potential and population genetic principles. As adaptations can typically be achieved through many different combinations of adaptive alleles (redundancy), the authors describe how two characteristics – heterogeneity among loci and non-parallelism between replicated populations – are features for the characterization of polygenic adaptation in evolving populations and how this uniform framework can be applied to natural and experimental populations.

Powerful method for analysing genetic adaptations

According to first author Neda Barghi from the Institute of Population Genetics at Vetmeduni Vienna, both experimental evolution and natural populations with parallel phenotypic evolution offer enormous potential for studying non-parallelism and heterogeneity in order to understand the genetic basis of adaptation. “We anticipate that the combination of time-series data with replicate populations will be a particularly powerful method to uncover the genetic architecture of adaptation,” says Barghi.

From the experimental study to a better understanding of evolution in nature

Of particular interest, according to the researchers, are specifically designed experimental evolution studies, both in the laboratory and whenever possible also in natural settings. Smaller population sizes increase genetic drift, resulting in more heterogeneity within populations and non-parallelism among populations, but with a sufficient level of replication it is possible to obtain reliable signatures that can be distinguished from neutral variation. Reducing the number of adaptive alleles by starting experiments with a small number of founders will result in stronger selection responses of individual alleles, providing the potential of further follow-up functional characterization,” says Christian Schlötterer, head of the Institute of Population Genetics at Vetmeduni Vienna. Once the adaptive architecture of a trait is well-characterized by experimental evolution studies, the research team believes it will be possible to expand the focus to natural populations to understand their dynamics in complex systems.

The article “Polygenic adaptation: a unifying framework to understand positive selection” by Neda Barghi, Joachim Hermisson and Christian Schlötterer was published in Nature Reviews Genetics.