Specialization and interchangeability of the cellulose synthase complex
- Cellulose is an essential component of the plant cell wall, where it serves as the major load bearing structure. Cellulose is synthesized by cellulose synthases (CESAs), which act in a large complex at the plasma membrane. In Arabidopsis, certain primary CESAs synthesize the primary cell wall, while others synthesize the secondary cell wall. Both the primary complex and the secondary complex are composed of three distinct genetic positions which are filled by specialized isoforms. It this thesis, I analyze the sequences of the cellulose synthase family to show that these genetic positions reflect a specialization found in all seed plants. I identify a number of regions within the CESA sequences which may be responsible for the specialized "class-specific" properties of these CESAs. By generating catalytic inactivations to various primary CESAs, I show that a catalytically inactivated CESA6 construct is able to rescue a CESA6 null mutant, while a catalytically inactivated CESA3 construct is unable to rescue its respective mutant. This indicates differences in the importance of catalytic activity between CESAs. Because the CESA6 family is the most expanded, this suggests that control of cellulose properties could occur through regulation of CESA6 catalytic activity. I demonstrate that expressing the secondary CESA7, it is possible to partially rescue a mutation to the primary CESA3 gene, even though the CESA3 and CESA7 families diverged early in plant evolution and no primary CESAs can rescue other primary CESA mutants. This suggests that the primary and secondary complexes share a common architecture with limited interchangeability. Finally, I characterize two fluorescent dyes which bind preferentially to cellulose and which are suitable for confocal microscopy. These dyes allow cellulose fibrils to be visualized in vivo for the first time. This revealed that cellulose fibrils reorient over the course of root cell elongation, generating a multilaminar network strengthened against forces along all axes from a set of microfibrils which are initially synthesized in a transverse orientation at the membrane.
|Type of resource
|electronic; electronic resource; remote
|1 online resource.
|Carroll, Andrew Walker
|Stanford University, Department of Biology.
|Statement of responsibility
|Andrew Walker Carroll.
|Submitted to the Department of Biology.
|Ph.D. Stanford University 2011
- © 2011 by Andrew Walker Carroll
- This work is licensed under a Creative Commons Attribution 3.0 Unported license (CC BY).
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