Translocation of virulence factors to host plant cells by agrobacterium tumefaciens / Colleen A. McCullen.

Format:

Book

Manuscript

Microformat

Thesis/Dissertation

Author/Creator:

McCullen, Colleen A.

Contributor:

Binns, Andrew N., advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Penn dissertations--Cell and molecular biology.

Cell and molecular biology--Penn dissertations.

Cell and Molecular Biology.

Academic Dissertations as Topic.

Medical Subjects:

Cell and Molecular Biology.

Academic Dissertations as Topic.

Local Subjects:

Penn dissertations--Cell and molecular biology.

Cell and molecular biology--Penn dissertations.

Physical Description:

xii, 179 pages : illustrations ; 29 cm

Production:

2003.

Summary:

Agrobacterium tumefaciens causes Crown Gall disease on a wide variety of plants by transporting a single-stranded piece of DNA (the T-DNA) into plant cells. Translocation of the T-DNA by A. tumefaciens requires the virB-virD4-encoded type IV secretion system (T4SS). VirE2, a single-stranded DNA binding protein, is also translocated to host cells via the T4SS, where it associates with the T-DNA and mediates T-DNA uptake into the nucleus and integration into the host genome. Mutagenesis of virE2 revealed a region near the C-terminus of the gene product that is required for function in the bacterium but not in the plant cell. Mutations in this region rendered VirE2 unable to complement for virulence in A. tumefaciens. However, transgenic tobacco plants producing C-terminal mutant forms of VirE2 were able to complement the virulence of a virE2- strain of A. tumefaciens . This finding led to the hypothesis that a secretion signal may be present near the C-terminus of VirE2 and mutations in this region disrupted VirE2 translocation to plant cells. When produced in A. tumefaciens , the C-terminal mutant forms of VirE2 did not block the translocation apparatus and may, therefore, not be targeted for export. VirE2 is found in the cytoplasm, membranes and periplasm of the bacterial cell. The hypothesis that the putative C-terminal secretion signal is required for targeting of VirE2 to the cell envelope was tested. The C-terminal mutant forms of VirE2 were found in each compartment of the cell at levels similar to wild-type VirE2. The presence of Osa, a protein that suppresses VirE2 transport to plant cells, did not block VirE2 localization to the periplasm or membranes. Furthermore, targeting of VirE2 to the periplasm via the sec pathway resulted in degradation of the protein. The findings described above are consistent with a model in which VirE2 and the T-DNA are transported independently via the T4SS into plant cells.

Notes:

Adviser: Andrew N. Binns.

Thesis (Ph.D. in Cell and Molecular Biology) -- University of Pennsylvania, 2003.

Includes bibliographical references.

Local Notes:

University Microfilms order no.: 3109202.

OCLC:

244973306