Dynamics and liquid-like behavior of the pyrenoid of the green alga chlamydomonas reinhardtii
Abstract/Contents
- Abstract
- Approximately 30--40% of global CO2 fixation occurs inside a non-membrane-bound organelle called the pyrenoid. Pyrenoids are found in chloroplasts of most eukaryotic algae and some hornworts, and are densely packed with the carbon-fixing enzyme Rubisco. The pyrenoid is a core component of the algal carbon concentrating mechanism (CCM), which enables more efficient inorganic carbon capture than that of most land plants by supplying Rubisco with a high concentration of its substrate, CO2. In this thesis, I show that, in contrast to long-held assumptions of the field, the pyrenoid matrix is not a solid crystal, but is strikingly dynamic, and can likely be considered a phase-separated, liquid-like organelle. The studies detailed in the following chapters focus on the dynamics of fluorescently-tagged pyrenoid proteins in live cells of the model green alga Chlamydomonas reinhardtii, assayed by state-of-the-art quantitative fluorescence microscopy techniques. I tracked the inheritance of fluorescently labeled pyrenoids in live cells for the first time, and observe that pyrenoids are primarily inherited by fission, but that de novo growth is also possible. Strikingly, I have discovered that much of the pyrenoid matrix rapidly disperses into the chloroplast stroma immediately before division and quickly re-aggregates afterwards, suggesting that pyrenoid components undergo a phase transition during division. Furthermore, I demonstrate through Fluorescence Recovery After Photobleaching (FRAP) experiments that the major protein components of the pyrenoid matrix undergo rapid internal mixing. Finally, by targeting a genetically encoded pH fluorescent biosensor to the pyrenoid matrix, I have shown that the pH of the pyrenoid increases during photosynthesis, like the stroma. These findings strongly suggest that the pyrenoid matrix undergoes liquid mixing as a phase-separated compartment in equilibrium with the stroma. This new view of the pyrenoid matrix as a phase-separated compartment resolves the paradox of how the chaperone Rubisco Activase can access Rubisco throughout the pyrenoid matrix. More broadly, my findings provide a new paradigm for understanding the structure, regulation, and inheritance of the pyrenoid, new facts that can be used to guide future attempts to engineer such compartments into higher plants.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2017 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Freeman Rosenzweig, Elizabeth Sarah | |
|---|---|---|
| Associated with | Stanford University, Department of Biology. | |
| Primary advisor | Jonikas, Martin | |
| Primary advisor | Walbot, Virginia | |
| Thesis advisor | Jonikas, Martin | |
| Thesis advisor | Walbot, Virginia | |
| Thesis advisor | Berry, Joseph A, 1941- | |
| Thesis advisor | Feldman, Jessica L | |
| Thesis advisor | Mudgett, Mary Beth, 1967- | |
| Advisor | Berry, Joseph A, 1941- | |
| Advisor | Feldman, Jessica L | |
| Advisor | Mudgett, Mary Beth, 1967- |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Elizabeth S. Freeman Rosenzweig. |
|---|---|
| Note | Submitted to the Department of Biology. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2017. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2017 by Elizabeth Sarah Freeman Rosenzweig
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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