Dissertation
DECIPHERING FACTORS THAT DRIVE ROOT MORPHOGENESIS: CELL WALL-PHYTOHORMONE CROSSTALK AND A KINASE INVOLVED IN ROOT HAIR DEVELOPMENT
Doctor of Philosophy (PhD), Washington State University
01/2019
Handle:
https://hdl.handle.net/2376/111472
Abstract
Plant roots are essential for water and nutrient acquisition and are often the most rate-limiting organ for plant growth. The speed of root growth to acquire these crucial nutrients relies on the rate and duration of cell expansion. In turn, cellular expansion depends on the biomechanical properties of the cell wall balancing both biosynthesis and extensibility. In order to study the regulation of cell wall biosynthesis we used the radially swollen 1 (rsw1) conditional allele of CELLULOSE SYNTHASE A (CESA). We found that exogenous application of auxin, brassinosteroids, jasmonate, cytokinin, and salicylic acid reduced isotropic swelling in rsw1 roots, while ethylene and gibberellic acid exacerbate swelling. However, brassinosteroids are the only phytohormone that both reduce isotropic swelling and enhance primary root growth. We also uncovered altered auxin and brassinosteroid transport/signaling in rsw1, at both the restrictive and permissive temperatures. In particular, we found reduced abundance of AUX1, an auxin influx carrier in rsw1, implicating the importance of auxin influx in anisotropic growth and we also found reduced PIN2 abundance in rsw1, an auxin efflux carrier.
In addition to the rate of growth, the overall root surface area plays a vital role in nutrient and water acquisition. Proliferation of root hairs greatly enhances the overall root/soil interface. Previous root hairless mutants have displayed a reduction in shoot, root, and overall plant yield. We investigated the root hairless mutant (buzz) in Brachypodium distachyon, which displays increased root growth rate and no impact on shoot biomass or yield. We discovered the buzz phenotype is due to a mutation in a putative cell division kinase crucial for tip growth. Furthermore, we examined the previously uncharacterized Arabidopsis thaliana ortholog of buzz, which displays a short root hair phenotype. From our data we propose that B. distachyon buzz (Bdbuzz) and A. thaliana buzz (Atbuzz) act at different steps in root hair development i.e. post initiation tip growth versus determining the duration of tip growth. Overall the studies in this dissertation contribute to the fundamental understanding of cell wall regulation through hormone crosstalk and the mechanism of root hair growth in monocots for improvement of agriculture cereals.
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Details
- Title
- DECIPHERING FACTORS THAT DRIVE ROOT MORPHOGENESIS: CELL WALL-PHYTOHORMONE CROSSTALK AND A KINASE INVOLVED IN ROOT HAIR DEVELOPMENT
- Creators
- Thiel A Lehman
- Contributors
- Karen A Sanguinet (Advisor)Michael Neff (Committee Member)Andrei Smertenko (Committee Member)Asaph Cousins (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Crop and Soil Sciences, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 296
- Identifiers
- 99900581505601842
- Language
- English
- Resource Type
- Dissertation