Title page for ETD etd-05112007-152300

Type of Document Master's Thesis
Author Petzold III, Herman Earl
Author's Email Address epetzold@vt.edu
URN etd-05112007-152300
Title Promoter Deletion Analysis of Xylem Cysteine Protease 2 (XCP2) in Arabidopsis thaliana
Degree Master of Science
Department Horticulture
Advisory Committee
Advisor Name Title
Beers, Eric P. Committee Chair
Nowak, Jerzy Committee Member
Welbaum, Gregory E. Committee Member
  • tracheary element
  • Arabidopsis thaliana
  • cysteine protease
  • promoter deletion
  • xylem
Date of Defense 2007-05-02
Availability unrestricted
The process of xylem tracheary element differentiation involves the coordination of vascular cambium activity, cell fate determination, cell expansion/elongation, secondary wall synthesis, programmed cell death, and cellular autolysis. The end result of tracheary element differentiation is a cellular corpse lacking a protoplast and consisting of a thickened cell wall composed mostly of lignin and cellulose. Little is known about the genetic mechanisms regulating the process of tracheary element differentiation. XCP2 expression localizes to tracheary elements according to two independent methods of analysis: promoter reporter experiments and immunogold localization by electron microscopy. XCP2 may be involved in catalyzing the degeneration of the protoplast during the final autolytic stages of tracheary element differentiation. To this date XCP2 function has not been directly demonstrated. In principle, any tracheary element-specific markers can be linked to upstream regulatory genes with roles in tracheary element differentiation. To develop the XCP2 promoter as a tool for identification of transacting factors, a promoter deletion analysis was carried out. Utilizing information from 5’ and 3’ deletion constructs, a 70-bp region upstream of the XCP2 translational start site is both necessary and sufficient for TE-specific expression of the UidA reporter gene. Mutational analysis of the ACTTTA element at position -113-bp strongly suggests it is a cis element required for XCP2 expression. In silico analysis of an 18-bp promoter region located within 200-bp of the translation start site and including the ACTTTA element revealed high indentity shared between xylem-specific XCP2 homologs from Zinnia elegans, Populus trichocarpa, and XCP1 from Arabidopsis thaliana.
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