Dissertation
MACERATOR: A Novel, Plant-Specific Microtubule-Nucleator
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000003155
Handle:
https://hdl.handle.net/2376/123004
Abstract
The permanence and rigidity of the plant cell wall means accuracy of tissue patterning duringplant organ formation is highly regulated. The orientation of the partition between daughter cells,
known as the cell plate, during cytokinesis directly affects tissue patterns. The cell plate is
synthetized by the phragmoplast, a plant-specific cellular machine composed of microtubules, a
vesicle trafficking system, and cell wall synthesis enzymes. Phragmoplast microtubules form two
concentric rings that sandwich the midzone where cell plate vesicles are delivered and fuse then
smooth. Dynamic microtubules allow the phragmoplast to deposit the cell plate as it expands to
reach the mother cell wall at the cortical division zone. Microtubules depolymerize when the cell
plate reaches maturity to create a pool of free tubulin, which can be recycled to nucleate nascent
microtubules on the leading edge of the phragmoplast. Leading edge microtubules guide delivery
of vesicles on the centrifugal edge of the smoothing cell plate. Behavior of microtubules in any
microtubule array is governed by microtubule-associated proteins (MAPs) which in turn are
regulated by cellular cues. Although the phragmoplast is unique to plants, most microtubule
associated proteins found there are conserved in all eukaryotes. The main hypothesis of my work
is that the phragmoplast requires plant-specific MAPs. This research focuses on characterizing
the plant-specific MAP family, MACERATOR. MACERATOR4 binds microtubules, promotes
microtubule nucleation, and regulates phragmoplast length. Currently, known microtubule
nucleating factors are the conserved γ-tubulin ring complex (γ-TuRC) and TPX2 (Targeting
protein for Xklp2). This work reports a novel land-plant specific nucleating factor and its role in
phragmoplast organization. MACERATOR4 localizes to nucleation sites in vivo and promotes
microtubule nucleation in vitro. MACERATOR4 likely functions in a feedback loop to tightly
regulate the amount of free tubulin in the phragmoplast. Understanding this mechanism
contributes to a developing model of microtubule turnover during cell division. Phragmoplast
expansion enables cytokinesis in long, rigid conductive cells that were necessary for plants to
colonize land. Outcomes of my work would help to understand the relationship between
phragmoplast evolution and colonization of land by plants.
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Details
- Title
- MACERATOR: A Novel, Plant-Specific Microtubule-Nucleator
- Creators
- Sharol Anna Marcec
- Contributors
- Andrii Smertenko (Advisor)Michael Neff (Committee Member)Michael Knoblauch (Committee Member)Karen Sanguinet (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Agricultural, Human, and Natural Resource Sciences, College of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 209
- Identifiers
- 99900652004001842
- Language
- English
- Resource Type
- Dissertation