Accumulation of spontaneous mutations in the ciliate Tetrahymena thermophila Journal Article

Author(s): Long, Hongan; Paixão, Tiago; Azevedo, Ricardo B; Zufall, Rebecca A
Article Title: Accumulation of spontaneous mutations in the ciliate Tetrahymena thermophila
Affiliation IST Austria
Abstract: Knowledge of the rate and fitness effects of mutations is essential for understanding the process of evolution. Mutations are inherently difficult to study because they are rare and are frequently eliminated by natural selection. In the ciliate Tetrahymena thermophila, mutations can accumulate in the germline genome without being exposed to selection. We have conducted a mutation accumulation (MA) experiment in this species. Assuming that all mutations are deleterious and have the same effect, we estimate that the deleterious mutation rate per haploid germline genome per generation is U = 0.0047 (95% credible interval: 0.0015, 0.0125), and that germline mutations decrease fitness by s = 11% when expressed in a homozygous state (95% CI: 4.4%, 27%). We also estimate that deleterious mutations are partially recessive on average (h = 0.26; 95% CI: –0.022, 0.62) and that the rate of lethal mutations is <10% of the deleterious mutation rate. Comparisons between the observed evolutionary responses in the germline and somatic genomes and the results from individual-based simulations of MA suggest that the two genomes have similar mutational parameters. These are the first estimates of the deleterious mutation rate and fitness effects from the eukaryotic supergroup Chromalveolata and are within the range of those of other eukaryotes.
Keywords: protist, deleterious mutation rate, dominance, lethal mutations mutational, robustness
Journal Title: Genetics
Volume: 195
Issue 2
ISSN: 0016-6731
Publisher: Genetics Society of America  
Date Published: 2013-10-01
Start Page: in press
Copyright Statement: Copyright © 2013 by the Genetics Society of America
DOI: 10.1534/genetics.113.153536
Notes: We thank Peter Keightley, Rolf Lohaus, and Tim Cooper for useful advice and technical support, Sujal Phadke, Kevin J. Spring, Joe West, Patrícia Brito, and Ian Dworkin for helpful discussions, and three anonymous reviewers for valuable insight. The Tetrahymena Stock Center at Cornell University provided the SB210 and B*VII strains. This research was supported in part by the National Institute of General Medical Science of the National Institutes of Health (award no. R01GM101352 to R.A.Z. and R.B.R.A.), the European Research Council (Advanced Grant ERC-2009-AdG-250152 SELECTIONINFORMATION, T.P.), Sigma Xi GIAR (H.L.), the Wissenschaftskolleg zu Berlin (R.B.R.A.), and the University of Houston GEAR (R.A.Z.).
Open access: yes (repository)
IST Austria Authors
  1. Tiago Paixão
    27 Paixão