Dissertation
ROLES AND INTERPLAY OF ION TRANSPORT PROTEINS IN PLASTID PHYSIOLOGY
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000003340
Handle:
https://hdl.handle.net/2376/122681
Abstract
Ion channels and transporters are present in membranes of all living cells. As integral membrane proteins, they can sense and transduce the chemical environment to other cells and cell compartments. Additionally, ion transport proteins affect membrane voltage, balance substrate and water flux, are involved in signaling processes, and help protect cells from damage. In the chloroplast, the plant organelle harboring the photosynthetic apparatus, knowledge about the physiological role of many ion transport proteins is limited. Due to the importance of photosynthesis, it is necessary to uncover the full potential of chloroplast transport proteins, particularly those that use the ion potassium (K+) as substrate. K+ is highly abundant in cells and fulfills many roles in plant and plastid physiology. This dissertation describes the roles of transport proteins inside chloroplasts of Arabidopsis thaliana. We characterized novel proteins, adding to the chloroplast transportome, discovered unidentified connections between protein families, and revisited the localization and function of another previously described transporter. First, we investigated putative K+-permeable ion channels in the chloroplast envelope membrane. Even though the mechanism has been described before, the molecular identity of these proteins was unknown. Candidate proteins PLASTID ENVELOPE ION CHANNEL1/2 (PEC1/2) are localized to the plastid envelope and exhibit K+-permeability but are most likely not required for K+ homeostasis since pec1pec2 mutants displayed no apparent phenotypic abnormalities. However, we found that PEC1/2 play a crucial role in chloroplast Ca2+ signaling. Secondly, we examined the interplay of two different ion transport proteins implicated in osmoregulation of plastids, K+-EFFLUX ANTIPORTER1 (KEA1) and MscS-LIKE2 (MSL2). The simultaneous lack of both proteins in kea1msl2 mutants resulted in novel phenotypic anomalies, pointing to a concerted function of both proteins. Finally, we studied the localization and role of putative envelope Na+:H+ ANTIPORTER NHD1 and found evidence for a thylakoid membrane localization in different approaches. In addition, investigations of nhd1 mutants revealed the importance of the carrier NHD1 in acclimation to fluctuating light conditions. Overall, this dissertation advanced our understanding of chloroplast ion transport proteins, subcellular Ca2+ signaling, and chloroplast homeostasis.
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Details
- Title
- ROLES AND INTERPLAY OF ION TRANSPORT PROTEINS IN PLASTID PHYSIOLOGY
- Creators
- Carsten Voelkner
- Contributors
- Michael Knoblauch (Advisor)Hans-Henning Kunz (Committee Member)Asaph B. Cousins (Committee Member)Helmut Kirchhoff (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Biological Sciences, School of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 167
- Identifiers
- 99900652103201842
- Language
- English
- Resource Type
- Dissertation