Prions: Roles in Development and Adaptive Evolution

Prions are often considered as anomalous proteins associated primarily with disease rather than as a fundamental source of diversity within biological proteomes. Whereas this longstanding viewpoint has its genesis in the discovery of the original namesake prions as causative agents of several complex diseases, the underlying assumption of a strict disease basis for prions could not be further from the truth. Prions and the spectrum of functions they comprise, likely represent one of the largest paradigm shifts concerning molecular-encoded phenotypic diversity since identification of DNA as the principle molecule of heredity. The ability of prions to recruit similar proteins to alternate conformations may engender a reservoir of diversity supplementing the genetic diversity resulting from stochastic mutations of DNA and subsequent natural selection. Here we present several currently known prions and how many of their functions as well as modes of transmission are intricately linked to adaptation from an evolutionary perspective. Further, the stability of some prion conformations across generations indicates that heritable prion-based adaptation is a reality.