Genetics. Published Articles Ahead of Print: January 19, 2009, Copyright © 2009
doi:10.1534/genetics.108.100297


A more recent version of this article appeared on March 1, 2009.


REGULAR RESEARCH PAPERS

The Strength of Selection Against the Yeast Prion [PSI+]

1 University of Arizona
2 University of Guelph

* To whom correspondence should be addressed. E-mail: masel{at}u.arizona.edu.

Submitted on December 30, 2008
Revised on January 8, 2009
Accepted on 10 January 2009


Abstract

The [PSI+] prion causes widespread readthrough translation and is rare in natural populations of Saccharomyces, despite the fact that sex is expected to cause it to spread. Using the recently estimated rate of Saccharomyces outcrossing, we calculate the strength of selection necessary to maintain [PSI+] at levels low enough to be compatible with data. Using the best available parameter estimates, we find selection against [PSI+] to be significant. Inference regarding selection on modifiers of [PSI+] appearance depends on obtaining more precise and accurate estimates of the product of yeast effective population size Ne and the spontaneous rate of [PSI+] appearance m. The ability to form [PSI+] has persisted in yeast over a long period of evolutionary time, despite a diversity of modifiers that could abolish it. If mNe < 1, this may be explained by insufficiently strong selection. If mNe > 1, then selection should have favored the spread of [PSI+] resistance modifiers. In this case, rare conditions where [PSI+] is adaptive may permit its persistence in the face of negative selection.

Key Words: inbreeding, indirect selection, nonsense suppression, population genetics, readthrough translation




This article has been cited by other articles:


Home page
GeneticsHome page
A. K. Lancaster, J. P. Bardill, H. L. True, and J. Masel
The Spontaneous Appearance Rate of the Yeast Prion [PSI+] and Its Implications for the Evolution of the Evolvability Properties of the [PSI+] System
Genetics, February 1, 2010; 184(2): 393 - 400.
[Abstract] [Full Text] [PDF]