Dissertation
Are All Plastids Created Equal?: Diversity, Function, and Evolution of Plastid-targeted Genes and Chloroplast Transit Peptides in Plants
Washington State University
Doctor of Philosophy (PhD), Washington State University
07/2019
DOI:
https://doi.org/10.7273/000005555
Abstract
Plastids are morphologically and biochemically diverse organelles which not only perform photosynthesis but are also responsible for a wide range of metabolic, storage, regulatory, and aesthetic functions. The majority of plastid proteins are encoded by the nucleus and imported post-translationally, which allows for much greater spatiotemporal control of plastid function. Most of what is known about plastids has been studied in a relatively small group of model organisms, yet the myriad functions of plastids and significant microscopy evidence suggest that plastid function may be relatively unique in each plant species. Research in this dissertation aims to expand the field of plastid biology to non-model systems by (1) Reviewing the current state of literature to explore how the plastid proteome is shaped and how this process is regulated. How nuclear-encoded plastid-targeted proteins are imported has been enigmatic since the discovery of the main import channel, but recent evidence has helped to resolve the molecular mechanism and regulatory aspects of this process; (2) Establishing bioinformatics methods to characterize the plastid proteome quickly and efficiently in a range of plant species. A novel application of existing subcellular prediction techniques revealed that only 628-828 proteins are shared between the plastids of all assessed Angiosperms, but between 6- to 25-fold more proteins were specific to single species or taxonomic groups; (3) Analyzing mutational patterns leading to the evolution of novel chloroplast transit peptides. Insertions and deletions, particularly those that caused a shift of the transcriptional or translational start site, were responsible for the majority of novel transit peptides, implicating either exon shuffling as the dominant means of subcellular relocalization to the plastid; and, (4) Characterization of the N-terminal soluble domain of the conserved protein ALB3 when expressed from the chloroplast genome. Perturbations to chlorophyll fluorescence and ion homeostasis suggest that constitutive activation of the ALB3/SecY heterodimeric channel by substrate proteins induces permeability of the thylakoid membrane to leakage of protons and disruption of ion gradients. An overabundance of ALB3 in certain tissues may cause ion dysregulation, particularly for calcium, magnesium, and potassium.
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Details
- Title
- Are All Plastids Created Equal?
- Creators
- Ryan Wayne Christian
- Contributors
- Amit Dhingra (Chair)Helmut Kirchhoff (Committee Member) - Washington State University, Biological Chemistry, Institute ofHans Henning Kunz (Committee Member) - Washington State University, Biological Sciences, School ofEric Roalson (Committee Member) - Washington State University, Biological Sciences, School of
- Awarding Institution
- Washington State University
- Academic Unit
- Program in Molecular Plant Sciences
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 383
- Identifiers
- 99901054232801842
- Language
- English
- Resource Type
- Dissertation