Root Border Cell Development and Functions of Extracellular Proteins and DNA in Fungal Resistance at the Root Tip

Persistent Link:
http://hdl.handle.net/10150/195136
Title:
Root Border Cell Development and Functions of Extracellular Proteins and DNA in Fungal Resistance at the Root Tip
Author:
Wen, Fushi
Issue Date:
2009
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Soilborne plant pathogens are responsible for many of the major crop diseases worldwide. However, plant root tips are generally resistant to pathogen infections. The goal of this dissertation research is to understand the mechanism of this natural resistance by testing the hypothesis that root caps and root border cells control the rhizosphere community through the biological products which they deliver to the soil. Specific objectives of this dissertation project are 1) identifying, isolating, and characterizing the genes important for border cell development and for root exudates delivery, and 2) analyzing the function of extracellular macromolecules in root exudates in root tip-fungal pathogen interaction. The expression of a primary cell wall synthesis gene, PsFut1, encoding Pisum sativum fucosyltransferase, was characterized during border cell production, and the impact of silencing this gene on border cell development was examined. Another gene, BRDgal1, encoding β-galactosidase, was identified and characterized in Pisum sativum during this study. It was shown that this β-galactosidase is specifically produced in and secreted from root border cells. The microarray transcriptional profiling in M. truncatula and mRNA differential display analysis in pea plants were carried out following the induction of border cell production to gain a broader understanding of the genes which potentially influence border cell development. In order to study the commonality of border cell production across different plant species, the expression of rcpme1, the marker gene for border cell production, was compared between the garden pea and a gymnosperm species, the Norway spruce (Picea abies). To accomplish the second objective, the focus of this study was shifted from border cell development to mucilaginous root exudates excreted by border cells and root cap cells. This resulted in a breakthrough in the understanding of the mechanisms of root tip resistance. The presence of extracellular DNA in the root mucilage was discovered and its requirement for root tip resistance to fungal infection was demonstrated. Extracellular proteins in the root mucilage were identified and they were shown to be also required for the root tip resistance to fungal infection. This work provided new insights into understanding plant defense mechanisms.
Type:
text; Electronic Dissertation
Keywords:
Border Cells; Extracellular DNA; Extracellular proteins; Nectria haematococca; Pisum sativum; Root fungal diseases
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Plant Science; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Hawes, Martha C.
Committee Chair:
Hawes, Martha C.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleRoot Border Cell Development and Functions of Extracellular Proteins and DNA in Fungal Resistance at the Root Tipen_US
dc.creatorWen, Fushien_US
dc.contributor.authorWen, Fushien_US
dc.date.issued2009en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractSoilborne plant pathogens are responsible for many of the major crop diseases worldwide. However, plant root tips are generally resistant to pathogen infections. The goal of this dissertation research is to understand the mechanism of this natural resistance by testing the hypothesis that root caps and root border cells control the rhizosphere community through the biological products which they deliver to the soil. Specific objectives of this dissertation project are 1) identifying, isolating, and characterizing the genes important for border cell development and for root exudates delivery, and 2) analyzing the function of extracellular macromolecules in root exudates in root tip-fungal pathogen interaction. The expression of a primary cell wall synthesis gene, PsFut1, encoding Pisum sativum fucosyltransferase, was characterized during border cell production, and the impact of silencing this gene on border cell development was examined. Another gene, BRDgal1, encoding β-galactosidase, was identified and characterized in Pisum sativum during this study. It was shown that this β-galactosidase is specifically produced in and secreted from root border cells. The microarray transcriptional profiling in M. truncatula and mRNA differential display analysis in pea plants were carried out following the induction of border cell production to gain a broader understanding of the genes which potentially influence border cell development. In order to study the commonality of border cell production across different plant species, the expression of rcpme1, the marker gene for border cell production, was compared between the garden pea and a gymnosperm species, the Norway spruce (Picea abies). To accomplish the second objective, the focus of this study was shifted from border cell development to mucilaginous root exudates excreted by border cells and root cap cells. This resulted in a breakthrough in the understanding of the mechanisms of root tip resistance. The presence of extracellular DNA in the root mucilage was discovered and its requirement for root tip resistance to fungal infection was demonstrated. Extracellular proteins in the root mucilage were identified and they were shown to be also required for the root tip resistance to fungal infection. This work provided new insights into understanding plant defense mechanisms.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectBorder Cellsen_US
dc.subjectExtracellular DNAen_US
dc.subjectExtracellular proteinsen_US
dc.subjectNectria haematococcaen_US
dc.subjectPisum sativumen_US
dc.subjectRoot fungal diseasesen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplinePlant Scienceen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorHawes, Martha C.en_US
dc.contributor.chairHawes, Martha C.en_US
dc.contributor.committeememberVanEtten, Hans D.en_US
dc.contributor.committeememberPierson, Leland S., IIIen_US
dc.contributor.committeememberTax, Frans E.en_US
dc.contributor.committeememberArnold, Anne Elizabethen_US
dc.identifier.proquest10642en_US
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