Biology Commons^™

An Efficient Pipeline To Generate Data For Studies In Plastid Population Genomics And Phylogeography, Brendan F. Kohrn, Jessica M. Persinger, Mitchell B. Cruzan

Biology Faculty Publications and Presentations

Premise of the study: Seed dispersal contributes to gene flow and is responsible for colonization of new sites and range expansion. Sequencing chloroplast haplotypes offers a way to estimate contributions of seed dispersal to population genetic structure and enables studies of population history. Whole‐genome sequencing is expensive, but resources can be conserved by pooling samples. Unfortunately, haplotype associations among single‐nucleotide polymorphisms (SNPs) are lost in pooled samples, and treating SNP allele frequencies as independent markers provides biased estimates of genetic structure.

Methods: We developed sampling methodologies and an application, CallHap, that uses a least‐squares algorithm to evaluate the fit between …

Adaptive Evolution Under Extreme Genetic Drift In Oxidatively Stressed Caenorhabditis Elegans, Stephen Fuller Christy, Riana I. Wernick, Michael James Lue, Griselda Velasco, Dana K. Howe, Dee R. Denver, Suzanne Estes

Biology Faculty Publications and Presentations

A mutation-accumulation (MA) experiment with Caenorhabditis elegans nematodes was conducted in which replicate, independently evolving lines were initiated from a low-fitness mitochondrial electron transport chain mutant, gas-1. The original intent of the study was to assess the effect of electron transport chain dysfunction involving elevated reactive oxygen species production on patterns of spontaneous germline mutation. In contrast to results of standard MA experiments, gas-1 MA lines evolved slightly higher mean fitness alongside reduced among-line genetic variance compared with their ancestor. Likewise, the gas-1 MA lines experienced partial recovery to wildtype reactive oxygen species levels. Whole-genome sequencing and analysis revealed that …

Paternal Mitochondrial Transmission In Intra-Species Caenorhabditis Briggsae Hybrids, Joseph A. Ross, Dana K. Howe, Anna Luella Coleman-Hulbert, Dee R. Denver, Suzanne Estes

Biology Faculty Publications and Presentations

To study mitochondrial-nuclear genetic interactions in the nematode Caenorhabditis briggsae, our three laboratories independently created 38 intra-species cytoplasmic-nuclear hybrid (cybrid) lines. Although the cross design combines maternal mitotypes with paternal nuclear genotypes, eight lines (21%) unexpectedly contained paternal mitotypes. All eight share in common ancestry of one of two genetically related strains. This unexpected parallel observation of paternal mitochondrial transmission, undesirable given our intent of creating cybrids, provides a serendipitous experimental model and framework to study the molecular and evolutionary basis of uniparental mitochondrial inheritance.

Mitochondrial Dna Sequence And Lack Of Response To Anoxia In The Annual Killifish Austrofundulus Limnaeus, Josiah T. Wagner, Florisela H. Chavez, Jason E. Podrabsky

Biology Faculty Publications and Presentations

The annual killifish Austrofundulus limnaeus inhabits ephemeral ponds in regions of Venezuela, South America. Permanent populations of A. limnaeus are maintained by production of stress-tolerant embryos that are able to persist in the desiccated sediment. Previous work has demonstrated that A. limnaeus have a remarkable ability to tolerate extended periods of anoxia and desiccating conditions. After considering temperature, A. limnaeus embryos have the highest known tolerance to anoxia when compared to any other vertebrate yet studied. Oxygen is completely essential for the process of oxidative phosphorylation by mitochondria, the intracellular organelle responsible for the majority of adenosine triphosphate production. Thus, …

Paths Of Heritable Mitochondrial Dna Mutation And Heteroplasmy In Reference And Gas-1 Strains Of Caenorhabditis Elegans, Riana I. Wernick, Suzanne Estes, Dana K. Howe, Dee R. Denver

Biology Faculty Publications and Presentations

Heteroplasmy—the presence of more than one mitochondrial DNA (mtDNA) sequence type in a cell, tissue, or individual—impacts human mitochondrial disease and numerous aging-related syndromes. Understanding the trans-generational dynamics of mtDNA is critical to understanding the underlying mechanisms of mitochondrial disease and evolution. We investigated mtDNA mutation and heteroplasmy using a set of wild-type (N2 strain) and mitochondrial electron transport chain (ETC) mutant (gas-1) mutant Caenorhabditis elegans mutation-accumulation (MA) lines. The N2 MA lines, derived from a previous experiment, were bottlenecked for 250 generations. The gas-1 MA lines were created for this study, and bottlenecked in the laboratory for …

Selfish Mitochondrial Dna Proliferates And Diversifies In Small, But Not Large, Experimental Populations Of Caenorhabditis Briggsae, Wendy S. Phillips, Anna Luella Coleman-Hulbert, Emily S. Weiss, Dana K. Howe, Sita Ping, Riana I. Wernick, Suzanne Estes, Dee R. Denver

Biology Faculty Publications and Presentations

Evolutionary interactions across levels of biological organization contribute to a variety of fundamental processes including genome evolution, reproductive mode transitions, species diversification, and extinction. Evolutionary theory predicts that so-called “selfish” genetic elements will proliferate when the host effective population size (N_e) is small, but direct tests of this prediction remain few. We analyzed the evolutionary dynamics of deletion-containing mitochondrial DNA (ΔmtDNA) molecules, previously characterized as selfish elements, in six different natural strains of the nematode Caenorhabditis briggsae allowed to undergo experimental evolution in a range of population sizes (N = 1, 10, 100, and 1,000) for a maximum …

In Vivo Quantification Reveals Extensive Natural Variation In Mitochondrial Form And Function In Caenorhabditis Briggsae, Kiley Ann Hicks, Dana K. Howe, Aubrey Leung, Dee R. Denver, Suzanne Estes

Biology Faculty Publications and Presentations

We have analyzed natural variation in mitochondrial form and function among a set of Caenorhabditis briggsae isolates known to harbor mitochondrial DNA structural variation in the form of a heteroplasmic nad5 gene deletion (nad5Δ) that correlates negatively with organismal fitness. We performed in vivo quantification of 24 mitochondrial phenotypes including reactive oxygen species level, membrane potential, and aspects of organelle morphology, and observed significant among- isolate variation in 18 traits. Although several mitochondrial phenotypes were non-linearly associated with nad5Δ levels, most of the among-isolate phenotypic variation could be accounted for by phylogeographic clade membership. In particular, isolate-specific mitochondrial membrane potential …

Pseudoscorpion Mitochondria Show Rearranged Genes And Genome-Wide Reductions Of Rna Gene Sizes And Inferred Structures, Yet Typical Nucleotide Composition Bias, Sergey Ovchinnikov, Susan E. Masta

Biology Faculty Publications and Presentations

Pseudoscorpions are chelicerates and have historically been viewed as being most closely related to solifuges, harvestmen, and scorpions. No mitochondrial genomes of pseudoscorpions have been published, but the mitochondrial genomes of some lineages of Chelicerata possess unusual features, including short rRNA genes and tRNA genes that lack sequence to encode arms of the canonical cloverleaf-shaped tRNA. Additionally, some chelicerates possess an atypical guanine-thymine nucleotide bias on the major coding strand of their mitochondrial genomes.

We sequenced the mitochondrial genomes of two divergent taxa from the chelicerate order Pseudoscorpiones. We find that these genomes possess unusually short tRNA genes that do …

Natural Variation In Life History And Aging Phenotypes Is Associated With Mitochondrial Dna Deletion Frequency In Caenorhabditis Briggsae, Suzanne Estes, Anna Luella Coleman-Hulbert, Kiley Ann Hicks, Gene De Haan, Sarah R. Martha, Jeremiah B. Knapp, Samson William Smith, Kevin C. Stein, Dee R. Denver

Biology Faculty Publications and Presentations

Background: Mutations that impair mitochondrial functioning are associated with a variety of metabolic and age-related disorders. A barrier to rigorous tests of the role of mitochondrial dysfunction in aging processes has been the lack of model systems with relevant, naturally occurring mitochondrial genetic variation. Toward the goal of developing such a model system, we studied natural variation in life history, metabolic, and aging phenotypes as it relates to levels of a naturally-occurring heteroplasmic mitochondrial ND5 deletion recently discovered to segregate among wild populations of the soil nematode, Caenorhabditis briggsae. The normal product of ND5 is a central component of the …