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Permanent link (DOI): https://doi.org/10.7939/R3VT18

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Pectin remodelling enzymes of flax and their roles in fiber development Open Access

Descriptions

Other title
Subject/Keyword
Pectinesterase
Galactan
Pectin methylesterase
Flax fiber
Cell wall
Homogalacturonan
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Pinzon Latorre, David
Supervisor and department
Deyholos, Michael (Biological Sciences)
Examining committee member and department
Hacke, Uwe (Renewable Resources)
Cooke, Janice (Biological Sciences)
Mansfield, Shawn (Wood Science, University of British Columbia)
Strelkov, Stephen (Agricultural, Food & Nutritional Science)
Department
Department of Biological Sciences
Specialization
Plant Biology
Date accepted
2014-04-16T15:54:55Z
Graduation date
2014-11
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Linum usitatissimum (flax) is an annual eudicot for which two types are cultivated: linseed and fiber flax. The stem fibers of linseed are not generally used commercially because they are of lower quality and yield than those obtained from fiber flax. Moreover, the extraction of fibers by dew-retting is not possible in the climate of Canada. Our goal was to study the pectin composition in the cell wall of the fibers and surrounding cells and find a set of candidate pectin-modifying genes with roles in fiber development. Flax phloem fibers elongate intrusively by diffuse growth, so, they need to penetrate between adjacent cells during elongation through the middle lamella. This is hypothesized to require dissolution of the middle lamella and sufficient rigidity of the fiber to allow penetration, while maintaining flexibility for cell wall expansion. The degree and pattern of methylesterification of galacturonic acid (GalA) residues in homogalacturonan (HG) influences the rigidity of the middle lamella and cell wall. Pectin methylesterases (PME) mediate the demethylesterification of GalA in muro, in either a block-wise fashion (resulting in rigidification), or random fashion (resulting in wall loosening via the subsequent action of polygalacturonases (PG) or pectate lyase like proteins (PLL). Through immunohistochemistry, I defined some of the modifications that occur in pectin during fiber elongation, and generated a model of fiber development, in which low methylesterification of elongating fibers is associated with abundant galactan side chains that help to regulate interactions between pectins and prevent premature rigidification of fiber cell wall during its growth. I characterized the PME, PMEI and PLL gene families in flax using the recently sequenced genome, and using transcript profiling assays on nine different stages of development I defined a set of candidate genes with roles in fiber development. I expressed one of these PMEIs in E. coli and demonstrated that it was able to inhibit most of the native PME activity in the upper portion of the flax stem. Together, these results clarify the role of pectin modification during bast fiber development and identify targets for crop improvement.
Language
English
DOI
doi:10.7939/R3VT18
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Pinzon-Latorre D, Deyholos MK: Characterization and transcript profiling of the pectin methylesterase (PME) and pectin methylesterase inhibitor (PMEI) gene families in flax (Linum usitatissimum). BMC Genomics 2013, 14:742.

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