Premium
TUNING A GENETIC SWITCH: EXPERIMENTAL EVOLUTION AND NATURAL VARIATION OF PROPHAGE INDUCTION
Author(s) -
Refardt Dominik,
Rainey Paul B.
Publication year - 2010
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.2009.00882.x
Subject(s) - prophage , lysogen , biology , genetic variation , natural selection , genetics , experimental evolution , selection (genetic algorithm) , evolutionary biology , gene , bacteriophage , escherichia coli , artificial intelligence , computer science
Genetic switches allow organisms to modulate their phenotype in response to environmental changes. Understanding the evolutionary processes by which switches are tuned is central to understanding how phenotypic variation is realized. Prophage induction by phage λ is the classic example of a genetic switch and allows λ to move between two different modes of transmission: as a lysogen it reproduces vertically as a component of the host genome; as a free phage it reproduces horizontally by infectious epidemic spread. We show that the λ switch can respond rapidly to selection for alteration in sensitivity and threshold. Sequencing of candidate genes in the genetic circuitry underlying the switch revealed mutations of likely adaptive significance in some, but not all candidates, suggesting that the core genetic circuitry plays a limited role in the fine‐tuning of the switch in vivo. The relative ease with which the switch could be tuned by selection was further indicated by extensive variation in sensitivity and threshold of its response function among wild lambdoid phages. Together, our findings emphasize the adaptive significance of a finely tuned switch and draw attention to the selective factors shaping prophage induction in natural phage populations.