Elucidation of secondary cell wall secretion mechanisms of Arabidopsis thaliana, Poplar (Populus deltoides x P. trichocarpa) and Pine (Pinus contorta)

Lignin is a key component of plant secondary cell walls, providing strength to the plant and allowing water transport. Lignin is a polymer of monolignols that are synthesized in the cell and transported into the cellulose rich cell wall. The primary goal of this thesis is to understand the mechanism...

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Main Author: Kaneda, Minako
Format: Others
Language:English
Published: University of British Columbia 2009
Subjects:
Online Access:http://hdl.handle.net/2429/3341
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spelling ndltd-LACETR-oai-collectionscanada.gc.ca-BVAU.-33412013-06-05T04:17:18ZElucidation of secondary cell wall secretion mechanisms of Arabidopsis thaliana, Poplar (Populus deltoides x P. trichocarpa) and Pine (Pinus contorta)Kaneda, MinakoMonolignolsAutoradiographyATP-binding cassetteSecondary cell wallHemicelluloseLigninHigh Pressure Freezing (HPF)(ABC) transportersLignin is a key component of plant secondary cell walls, providing strength to the plant and allowing water transport. Lignin is a polymer of monolignols that are synthesized in the cell and transported into the cellulose rich cell wall. The primary goal of this thesis is to understand the mechanism(s) of monolignol deposition during xylogenesis. The currently accepted theory is that monolignols are exported by Golgi-mediated vesicle delivery to the secondary cell wall. When this theory was re-examined using cryofixed developing pine, quantitative autoradiography showed that monolignols did not accumulate in Golgi but were rapidly translocated from cytosol to cell wall. This suggests alternative mechanisms, such as membrane transporters, work in monolignol export. ATP binding cassette (ABC) transporters were chosen because they transport other secondary metabolites and some ABC transporter encoding genes are highly expressed in lignifying cells. Four candidate ABC transporters were selected in Arabidopsis (ABCB11, ABCB14, ABCB15 from the ABCB/MDR subfamily and ABCG33 from the ABCG/PDR subfamily) and shown to have overlapping, high vasculature expression patterns. Mutants with T-DNA insertions in single ABC transporter genes had no change in lignification of inflorescence stems. However, a reduced polar auxin transport phenotype was detected in mutants of ABCB11, ABCB14 and ABCB15. An additional approach was the use of inhibitors of ABC transporters. A new assay, which was developed to quantify lignification in primary xylem of Arabidopsis roots, demonstrated that ABC inhibitors did not change lignin deposition. Monolignols are exported and polymerized in the polysaccharide matrix of the cell wall, which includes hemicelluloses that may organize monolignols during polymerization. Since diverse lignified cell types are enriched in either G- or S-lignin, I hypothesized that this pattern could reflect different hemicellulose distributions, which was examined using antibody labeling of xylans or mannans in hybrid poplar xylem. While xylans were generally distributed in all secondary cell walls, mannans were enriched in fibers but not in the ray and vessel walls. In summary, during secondary cell wall deposition, monolignols are exported by unknown transporter(s) rather than Golgi vesicles. In developing poplar wood, the monolignols are deposited into diverse hemicellulose domains in different cell types.University of British Columbia2009-01-05T21:54:42Z2009-01-05T21:54:42Z20082009-01-05T21:54:42Z2009-05Electronic Thesis or Dissertation9954411 bytesapplication/pdfhttp://hdl.handle.net/2429/3341eng
collection NDLTD
language English
format Others
sources NDLTD
topic Monolignols
Autoradiography
ATP-binding cassette
Secondary cell wall
Hemicellulose
Lignin
High Pressure Freezing (HPF)
(ABC) transporters
spellingShingle Monolignols
Autoradiography
ATP-binding cassette
Secondary cell wall
Hemicellulose
Lignin
High Pressure Freezing (HPF)
(ABC) transporters
Kaneda, Minako
Elucidation of secondary cell wall secretion mechanisms of Arabidopsis thaliana, Poplar (Populus deltoides x P. trichocarpa) and Pine (Pinus contorta)
description Lignin is a key component of plant secondary cell walls, providing strength to the plant and allowing water transport. Lignin is a polymer of monolignols that are synthesized in the cell and transported into the cellulose rich cell wall. The primary goal of this thesis is to understand the mechanism(s) of monolignol deposition during xylogenesis. The currently accepted theory is that monolignols are exported by Golgi-mediated vesicle delivery to the secondary cell wall. When this theory was re-examined using cryofixed developing pine, quantitative autoradiography showed that monolignols did not accumulate in Golgi but were rapidly translocated from cytosol to cell wall. This suggests alternative mechanisms, such as membrane transporters, work in monolignol export. ATP binding cassette (ABC) transporters were chosen because they transport other secondary metabolites and some ABC transporter encoding genes are highly expressed in lignifying cells. Four candidate ABC transporters were selected in Arabidopsis (ABCB11, ABCB14, ABCB15 from the ABCB/MDR subfamily and ABCG33 from the ABCG/PDR subfamily) and shown to have overlapping, high vasculature expression patterns. Mutants with T-DNA insertions in single ABC transporter genes had no change in lignification of inflorescence stems. However, a reduced polar auxin transport phenotype was detected in mutants of ABCB11, ABCB14 and ABCB15. An additional approach was the use of inhibitors of ABC transporters. A new assay, which was developed to quantify lignification in primary xylem of Arabidopsis roots, demonstrated that ABC inhibitors did not change lignin deposition. Monolignols are exported and polymerized in the polysaccharide matrix of the cell wall, which includes hemicelluloses that may organize monolignols during polymerization. Since diverse lignified cell types are enriched in either G- or S-lignin, I hypothesized that this pattern could reflect different hemicellulose distributions, which was examined using antibody labeling of xylans or mannans in hybrid poplar xylem. While xylans were generally distributed in all secondary cell walls, mannans were enriched in fibers but not in the ray and vessel walls. In summary, during secondary cell wall deposition, monolignols are exported by unknown transporter(s) rather than Golgi vesicles. In developing poplar wood, the monolignols are deposited into diverse hemicellulose domains in different cell types.
author Kaneda, Minako
author_facet Kaneda, Minako
author_sort Kaneda, Minako
title Elucidation of secondary cell wall secretion mechanisms of Arabidopsis thaliana, Poplar (Populus deltoides x P. trichocarpa) and Pine (Pinus contorta)
title_short Elucidation of secondary cell wall secretion mechanisms of Arabidopsis thaliana, Poplar (Populus deltoides x P. trichocarpa) and Pine (Pinus contorta)
title_full Elucidation of secondary cell wall secretion mechanisms of Arabidopsis thaliana, Poplar (Populus deltoides x P. trichocarpa) and Pine (Pinus contorta)
title_fullStr Elucidation of secondary cell wall secretion mechanisms of Arabidopsis thaliana, Poplar (Populus deltoides x P. trichocarpa) and Pine (Pinus contorta)
title_full_unstemmed Elucidation of secondary cell wall secretion mechanisms of Arabidopsis thaliana, Poplar (Populus deltoides x P. trichocarpa) and Pine (Pinus contorta)
title_sort elucidation of secondary cell wall secretion mechanisms of arabidopsis thaliana, poplar (populus deltoides x p. trichocarpa) and pine (pinus contorta)
publisher University of British Columbia
publishDate 2009
url http://hdl.handle.net/2429/3341
work_keys_str_mv AT kanedaminako elucidationofsecondarycellwallsecretionmechanismsofarabidopsisthalianapoplarpopulusdeltoidesxptrichocarpaandpinepinuscontorta
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