Welcome to the Estes Lab!

Welcome to the Estes lab in the Department of Biology at Portland State University. Our current research addresses the following topics, which we investigate using a variety of tools and approaches that include: laboratory experimental evolution with Caenorhabditis elegans and congeners, classical and molecular genetics and confocal microscopy.

Role of mutation in maladaptive & compensatory evolution

A main research focus is determining the population genetic patterns and molecular genetic underpinnings of fitness evolution and the role that new mutations play in the evolutionary process. Mutation is a fundamental evolutionary process that underlies genetic change in all populations. Most new mutations are detrimental for organismal health and fitness, although their genome-wide patterns and consequences are still poorly understood. The costs of such mutations can sometimes be ameliorated by compensatory evolution—the process whereby natural selection favors epistatic changes at loci that compensate for the deleterious effects of a mutant allele. Compensatory mutation is an important driving force in the evolution of antibiotic resistance and reproductive isolating mechanisms, and perhaps in providing a possible escape route for populations at risk for extinction.
We address the population-level consequences of compensatory mutation and the genetic mechanisms of evolution in collaboration with the Dee Denver lab (Oregon State Univ.). In particular, we use experimental evolution with strains of C. elegans containing mutant alleles affecting different mitochondrial electron transport chain (ETC) complexes. Because the mitochondrial ETC is crucial for eukaryotic life and because its proper functioning relies on the maintenance of favorable mitonuclear epistatic interactions, it is an ideal genetic system for studying the patterns and functional bases of deleterious and compensatory mutations.

Related questions include:

  • How do particular types of mitochondrial genetic damage influence mitochondrial and organismal physiology and fitness?

  • How is mitochondrial functioning related to organelle morphology and dynamics?

  • What forces control mitochondrial heteroplasmy levels within and across generations?


Mitochondrial function & life histories

A second avenue of research centers on the relationships between mitochondrial traits - primarily mitochondrial reactive oxygen species (ROS) levels and mitochondrial membrane potential -  and variation in life history and aging phenotypes. We have conducted the first surveys of natural variation in mitochondrial traits among natural populations of C. briggsae and recent experiments with C. elegans have tested the role of mitochondrial ROS in mediating life-history tradeoffs.

Our work has been supported by the National Science Foundation, the National Institutes of Health and the American Heart Association.

Recent publications

Joyner-Matos, J., K. A. Hicks*, D. Cousins, M. Keller, D. R. Denver, C. F. Baer, and S. Estes. 2013. Evolution of a higher intracellular oxidizing environment in Caenorhabditis elegans under relaxed selection. 2013. PLoS ONE 8: e65604.

Hicks, K. A.*, D. R. Denver, and S. Estes. 2013. Natural variation in Caenorhabditis briggsae mitochondrial form and function suggests a novel model of organelle dynamics. Mitochondrion 13: 44-51.

Hicks, K. A.*, D. R. Denver, D. K. Howe, A. Leung, and S. Estes. 2012. In vivo quantification of mitochondrial form and function in C. briggsae harboring a naturally occurring mtDNA deletion. PLoS ONE 7: e43837.

Clark, K. A., D. K. Howe, K. Gafner, D. Kusuma, S. Ping, S. Estes, and D. R. Denver. 2012. Selfish little circles: transmission bias and evolution of large deletion-bearing mitochondrial DNA in Caenorhabditis briggsae nematodes.  PLoS One 7: e41433.

Estes, S., P. C. Phillips, and D. R. Denver. 2011. Fitness recovery and compensatory evolution in natural mutant lines of C. elegans. Evolution. 65: no. doi: 10.1111/j.1558-5646.2011.01276.x.

Estes, S., A. L. Coleman-Hulbert*, K. A. Hicks*, G. de Haan*, D. K. Howe, S. R. Martha*, J. B. Knapp*, S. W. Smith*, K. C. Stein*, and D. R. Denver. 2011. Natural variation in life history and aging phenotypes is associated with mitochondrial DNA deletion frequency in Caenorhabditis briggsae. BMC Evolutionary Biology 11: 11.

Denver, D. R., D. Howe, L. Wilhelm, C. A. Palmer, J. L. Anderson, P. C. Phillips, K. C. Stein*, and S. Estes. 2010. Parallel mutation in independent paths of evolutionary recovery from mutational degradation in Caenorhabditis elegans. Genome Research. 20: 1663-1671.

*denotes PSU student author

last updated 12/21/12