Physiological regulatory networks: ecological roles and evolutionary constraints

Abstract

Ecological and evolutionary physiology has traditionally focused on aspects of physiology one at a time. Here, we discuss the implications of considering physiological regulatory networks (PRNs) as integrated wholes, a perspective that reveals novel roles for physiology in organismal ecology and evolution. For example, evolutionary response to changes in resource abundance might be constrained by the role of dietary micronutrients in immune response regulation, given a particular pathogen environment. Because many physiological components impact more than one process, organismal homeostasis is maintained, individual fitness is determined, and evolutionary change is constrained (or facilitated) by interactions within PRNs. We discuss how PRN structure and its system-level properties could determine both individual performance and patterns of physiological evolution. GlossaryAlternative physiological structures -Different PRN structures that would produce equivalent functional and fitness outcomes for a given species in a given environment. Which structure evolves might be largely random, but might have consequences for long-term evolution of PRN structure.Cytokines -Small cell-signalling proteins involved in intercellular communication. Regulatory cascades of cytokines are particularly critical in the immune system. Dysregulation -A breakdown over time in the ability of an individual's PRN to maintain homeostasis; possibly in response to chronic stress or infection, and possibly a root cause of aging.3 Homeostasis -A state of healthy physiological equilibrium, including appropriate anticipation of and responses to changing conditions.Integrator -A PRN molecule that has a particularly crucial role in synthesizing information (internal or external) and thereby determining multiple aspects of PRN functioning (e.g., a 'hub' or 'keystone' PRN molecule) Physiological Regulatory Network (PRN) -The network of molecules and their regulatory relationships that maintain and adjust homeostasis and facilitate performance at the wholeorganism level.PRN Molecule -PRN molecules are the subset of molecules that maintain homeostasis at the organism level via their regulatory relationships with other molecules. In most cases, these molecules are the nodes (vertices) in a PRN, and regulatory relationships between them are the links (edges). In some cases, several related molecules (e.g., circulating steroid, receptors, binding globulins) may be grouped together as a single node for measurement purposes, or gene activation may be a node in some contexts. Flexibility of node definition is common in other biological networks-for example, nodes in ecological networks can be species, groups of species, life stages, or other categories (e.g., detritus). PRN state -The concentrations of all PRN molecules at a given moment for a given individual in a particular context (e.g. age, time of year, life history stage). More generally, "changes in PRN state" describe joint adjustments in molecule concentrations in anticipation of or respo...

The Level of an Intracellular Antioxidant during Development Determines the Adult Phenotype in a Bird Species: A Potential Organizer Role for Glutathione

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