Evolutionary systems biology: links between gene evolution and function.

The recent accumulation of genome-wide data on various facets of gene expression, function and evolution stimulated the emergence of a new field, evolutionary systems biology. Many significant correlations were detected between variables that characterize the functioning of a gene, such as expression level, knockout effect, connectivity of genetic and protein-protein interaction networks, and variables that describe gene evolution, such as sequence evolution rate and propensity for gene loss. The first attempts on multidimensional analysis of genomic data yielded composite variables that describe the 'status' of a gene in the genomic community. However, it remains uncertain whether different functional variables affect gene evolution synergistically or there is a single, dominant factor. The number of translation events, linked to selection for translational robustness, was proposed as a candidate for such a major determinant of protein evolution. These developments show that, although the methodological basis of evolutionary systems biology is not yet fully solidified, this area of research is already starting to yield fundamental biological insights.