Spatial regulation of cellulose synthase trafficking
Abstract/Contents
- Abstract
- Plants owe their distinctive shapes, in large part, to the anisotropic expansion of constituent cells. During growth and development, a strong yet pliant cell wall constrains turgor-driven expansion along specific directions in the cell. This process relies on the function of two polymer arrays separated by the plasma membrane: the cortical microtubule cytoskeleton in the cytoplasm and the cellulose microfibril array in the cell wall. Live cell imaging previously confirmed that one function of the cortical microtubule array is to guide the trajectories of active cellulose synthase (CESA) complexes in the plasma membrane, thus orienting the deposition of nascent microfibrils. Here, I present evidence that cortical microtubules also position the delivery of CESA complexes to the plasma membrane and interact with small CESA-containing compartments by an unusual mechanism that permits motility driven by microtubule depolymerization. The association of CESA compartments with cortical microtubules is greatly enhanced during osmotic stress and other treatments that limit cellulose synthesis. Upon recovery from osmotic stress, delivery of CESA complexes to the plasma membrane is observed in association with microtubule-tethered compartments. While cortical microtubules appear to exert local control on CESA translocation and exocytosis, actin influences the global distribution of CESA at the plasma membrane. To study more general patterns of exocytosis, a probe based on the Arabidopsis SM protein KEULE was developed. Fluorescently labeled KEULE formed discrete, transient clusters at the plasma membrane, some of which coincided in space and time with the exocytosis of CESA complexes. Consistent with known SM function, KEULE facilitates vesicle fusion in growing plant cells. Thus, KEULE recruitment to the plasma membrane defines an intermediate step in the exocytosis of CESA and possibly other secreted cargo. KEULE localized preferentially near cortical microtubules and recent sites of cellulose synthesis, suggesting the microtubule cytoskeleton and nascent microfibrils define dynamic secretion domains at the plasma membrane. A genetic screen was conducted to identify factors that mediate the physical association of CESA, and organelles that traffic CESA, with the cortical microtubule cytoskeleton. I isolated two Arabidopsis mutants exhibiting reduced anisotropic growth, an inability to tether CESA-containing compartments to microtubules, and aberrant patterns of CESA motility at the plasma membrane. This phenotype is consistent with a general decoupling of CESA and microtubules. This thesis establishes new roles for the cortical microtubule cytoskeleton in organizing vesicular trafficking, and provides new genetic tools to examine the mechanism and regulation of CESA-microtubule interaction.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2011 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Gutierrez, Ryan |
|---|---|
| Associated with | Stanford University, Department of Biology. |
| Primary advisor | Bergmann, Dominique |
| Primary advisor | Ehrhardt, David (David Walter) |
| Thesis advisor | Bergmann, Dominique |
| Thesis advisor | Ehrhardt, David (David Walter) |
| Thesis advisor | Nelson, W. J. (W. James) |
| Thesis advisor | Stearns, Tim |
| Advisor | Nelson, W. J. (W. James) |
| Advisor | Stearns, Tim |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Ryan Gutierrez. |
|---|---|
| Note | Submitted to the Department of Biology. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2011. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2011 by Ryan Gutierrez
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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