Adaptive noise

Abstract

In biology, noise implies error and disorder and is therefore something which organisms may seek to minimize and mitigate against. We argue that such noise can be adaptive. Recent studies have shown that gene expression can be noisy, noise can be genetically controlled, genes and gene networks vary in how noisy they are and noise generates phenotypic differences among genetically identical cells. Such phenotypic differences can have fitness benefits, suggesting that evolution can shape noise and that noise may be adaptive. For example, gene networks can generate bistable states resulting in phenotypic diversity and switching among individual cells of a genotype, which may be a bet hedging strategy. Here, we review the sources of noise in gene expression, the extent to which noise in biological systems may be adaptive and suggest that applying evolutionary rigour to the study of noise is necessary to fully understand organismal phenotypes.

Keywords: bet hedging; evolution; variation.

Figure 1.

The expression of two genes (one red and one blue), among cells of one genotype, where circle size is a measure of expression. (a) Extrinsic noise is where there is similarity of expression of these genes within each cell but differences among the cells. (b) Intrinsic noise is where there is difference in expression of these genes within each cell.