Evolution of genetic switch complexity

The circuitry of the phage λ genetic switch determining the outcome of lytic or lysogenic growth is well-integrated and complex, raising the question as to how it evolved. It is plausible that it arose from a simpler ancestral switch with fewer components that underwent various additions and refinem...

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Bibliographic Details
Published in:Bacteriophage 2013-01, Vol.3 (1), p.e24186-1-e24186-5
Main Authors: Broussard, Gregory W., Hatfull, Graham F.
Format: Article
Language:English
Subjects:
Addendum
bistable
genetic circuits
genetic switch
integration-dependent immunity
lytic and lysogenic growth
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Summary:The circuitry of the phage λ genetic switch determining the outcome of lytic or lysogenic growth is well-integrated and complex, raising the question as to how it evolved. It is plausible that it arose from a simpler ancestral switch with fewer components that underwent various additions and refinements, as it adapted to vast numbers of different hosts and conditions. We have recently identified a new class of genetic switches found in mycobacteriophages and other prophages, in which immunity is dependent on integration. These switches contain only three genes (integrase, repressor and cro) and represent a major departure from the λ-like circuitry, lacking many features such as xis, cII and cIII. These small self-contained switches represent an unrealized, elegant circuitry for controlling infection outcome. In this addendum, we propose a model of possible events in the evolution of a complex λ-like switch from a simpler integration-dependent switch.
ISSN:2159-7073
2159-7081
2159-7081
DOI:10.4161/bact.24186