University of Tokyo
Macroscopic Theory for Phenotypic Adaptation and Evolution: Fluctuation-response, Genetic Assimilation, and Deep Linearity
Based on statistical physics and dynamical-systems theory, we present a macroscopic theory of fluctuation and responses in a biological system, to characterize its plasticity, robustness, and evolvability quantitatively. First, we discuss grand fluctuation-response relationship, i.e., proportionality between phenotypic responses against genetic evolution and by environmental adaptation as well as between phenotypic fluctuations due to genetic change and noise, as is confirmed both in experiments and simulations. This relationship is further formulated by sow-manifold hypothesis in which phenotypic changes after evolution are constrained along a dominant axis. For cells that undergo steady growth, this dominant axis corresponds to their growth-rate, where global proportionality in the responses of protein expression upon environmental changes is derived across thousands of genes, as is confirmed by adaptation experiments of bacteria under stress.