Item – Theses Canada

​
OCLC number
801165833
Link(s) to full text
LAC copy
LAC copy
Author
Reeves, Valerie,1975-
Title
Coniferin metabolism in the cambial region of Pinus strobus L.
Degree
Ph. D. -- University of New Brunswick, 2007
Publisher
Ottawa : Library and Archives Canada = Bibliothèque et Archives Canada, [2011]
Description
3 microfiches
Notes
Includes bibliographical references.
Abstract
<?Pub Inc> 'E'-Coniferin has only been detected in the cambial region of conifers during cambial activity, appearing prior to lignification and disappearing prior to cambial dormancy. Thus, its presence serves as an indicator that cambial growth is occurring. It follows then that the enzymes involved in coniferin metabolism, coniferin [beta]-glucosidase (CBG) and uridine 5'-diphosphoglucose: coniferyl alcohol glucosyltransferase (UDPG: CAGT), may be linked to regulation of the seasonal cycle of cambial growth and dormancy in conifers. In addition, these enzymes may also playa regulatory role in lignification in conifers, where CAGT sequesters coniferyl alcohol (CA) and CBG releases it. Thus, it is critical that we understand both CBG and CAGT. One of the roadblocks in CBG research is its cellular location. Reports conflict as to whether the enzyme is soluble or cell wall-bound. In this study, CBG activity was investigated in cambium and developing xylem of ' Pinus strobus' L. by a novel experimental approach. CA accumulated up to 28-fold in developing xylem during secondary wall formation, and also in actively dividing cambium cells. The findings strongly indicate that this abnormal CA accumulation was a result of CBG hydrolysis of coniferin, and also that CBG is a soluble catalyst in cambium and developing xylem of ' P. strobus'. Dormant cambium was not competent for CA production, indicating a temporal association between CBG and cambial activity. This is the first report of CBG activity in cambium cells. CAGT from 'P. strobus' was found to have higher activities for sinapyl alcohol, sinapaldehyde and coniferaldehyde, compared to coniferyl alcohol. CAGT Michaelis constants, Km, are reported for sinapaldehyde and coniferaldehyde for the first time. When dual substrates were administered to CAGT, the most pronounced product inhibition occurred when coniferyl alcohol and sinapaldehyde were administered together, with CAGT activity for sinapaldehyde being more strongly affected. This research also provides the first evidence for in vitro glucosylation of dihydroconiferyl alcohol by CAGT. Together, these findings, coupled with the discovery of seasonal patterns of CAGT activity toward coniferaldehyde and sinapaldehyde, indicate that CAGT has a prominent role in phenylpropanoid metabolism in relation to secondary growth.
ISBN
9780494693391
0494693398