Electronic Theses and Dissertations

Date

2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Biology

Committee Chair

Jennifer Mandel

Committee Member

Randall Bayer

Committee Member

Duane McKenna

Committee Member

Judith Cole

Abstract

Cytonuclear interactions in plants are the complex result of coevolution between the nuclear, mitochondrial, and plastid genomes. After several billion years of coevolution, metabolic activities are now tightly coordinated. Organellar genomes were believed to be under regulation by the nuclear genome, resulting in uniparental inheritance of small, non-recombining, and haploid organellar genomes. Apparent deviations from this coordination have often been perceived as deleterious to organismal fitness and not tolerated by natural selection. Recently, this assumption has been challenged. Although cytonuclear interactions are indeed highly coordinated, deviations are common. Across species, organellar genomes are cytoploid. They vary in size, recombine, and are neither strictly-uniparentally inherited nor haploid. A common state of organellar genomes is heteroplasmy intraindividual organellar genetic variation. Mitochondrial heteroplasmy is common throughout eukaryotes, as is plastid heteroplasmy in plants. Interest in cytonuclear interactions has grown, and the presence of two autonomous organellar genomes adds a level of complexity. Even though heteroplasmy is becoming recognized as a compounding factor in cytonuclear interactions, little research in plants has focused on the interface between these phenomena. Here, I present data on that interface using Daucus carota. I focused on how heteroplasmy may impact cytonuclear interactions at the individual level, the population level, and the level of genome evolution. I performed a long-term greenhouse study of individuals from across the range of D. carota to characterize phenotypic differences between heteroplasmic and non-heteroplasmic (homoplasmic) individuals. I then revealed patterns of linkage disequilibrium between and within organellar and nuclear genomes to determine if these patterns were consistent between heteroplasmic and homoplasmic individuals. While I do not suggest causation, this research demonstrates that heteroplasmy may impact aspects of cytonuclear interactions by affecting phenotypes and altering levels of nuclear and organellar linkage. Many new questions have arisen, as these results only address a small number of questions relating to heteroplasmy and cytonuclear interactions and offer a limited insight into this intriguing interplay of phenomena.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to ProQuest

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