Role of root border cells in the protection of the root tip from fungal infection

Persistent Link:
http://hdl.handle.net/10150/284151
Title:
Role of root border cells in the protection of the root tip from fungal infection
Author:
Gunawardena, Uvini Pulna
Issue Date:
2000
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:
Root microbe interactions are initiated generally in the region of elongation while the root tip remains infection free. In this dissertation, the hypothesis that root border cells play a role in protecting the root tip from fungal infections was examined. When radicles of pea seedlings were inoculated with Nectria haematococca , the zone of elongation became infected in the majority of the samples (ca. 90%) but the root tips appeared infection free and continued to grow essentially normally. However, microscopic evaluation revealed that N. haematococca propagules germinated and colonized border cells, leading to the formation of "mantles" that ensheathed the root tip. The tip tissue, nevertheless, remained infection free. Removing border cells prior to inoculation with the fungus or retarding their separation increased tip infections. Additionally, exudates from fungus inoculated root tips inhibited fungal growth in vitro when compared to those from uninoculated seedlings. When root tip infection occurred, a strong correlation between tip infection and cessation of further root growth was observed. In response to root tip infection by N. haematococca, a concomitant induction of border cell separation and defense gene expression in the tip was observed, suggesting that border cell separation may be a previously unrecognized alternative defense strategy of the pea root tip. The results are consistent with the following model: The separation of border cells, together with the presence of an inhibitory compound in the root exudates, minimizes contact between the fungus and the root tip thus protecting the tip from infection. Under conditions when tip infection does occur, the active induction of renewed border cell separation serves to remove infected tissue from the apical meristem area. Plant mutants altered in border cell separation can be used in the future studies to definitively establish the role of border cells in plant health.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Biology, Cell.; Agriculture, Plant Pathology.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Plant Diseases
Degree Grantor:
University of Arizona
Advisor:
Hawes, Martha C.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleRole of root border cells in the protection of the root tip from fungal infectionen_US
dc.creatorGunawardena, Uvini Pulnaen_US
dc.contributor.authorGunawardena, Uvini Pulnaen_US
dc.date.issued2000en_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.abstractRoot microbe interactions are initiated generally in the region of elongation while the root tip remains infection free. In this dissertation, the hypothesis that root border cells play a role in protecting the root tip from fungal infections was examined. When radicles of pea seedlings were inoculated with Nectria haematococca , the zone of elongation became infected in the majority of the samples (ca. 90%) but the root tips appeared infection free and continued to grow essentially normally. However, microscopic evaluation revealed that N. haematococca propagules germinated and colonized border cells, leading to the formation of "mantles" that ensheathed the root tip. The tip tissue, nevertheless, remained infection free. Removing border cells prior to inoculation with the fungus or retarding their separation increased tip infections. Additionally, exudates from fungus inoculated root tips inhibited fungal growth in vitro when compared to those from uninoculated seedlings. When root tip infection occurred, a strong correlation between tip infection and cessation of further root growth was observed. In response to root tip infection by N. haematococca, a concomitant induction of border cell separation and defense gene expression in the tip was observed, suggesting that border cell separation may be a previously unrecognized alternative defense strategy of the pea root tip. The results are consistent with the following model: The separation of border cells, together with the presence of an inhibitory compound in the root exudates, minimizes contact between the fungus and the root tip thus protecting the tip from infection. Under conditions when tip infection does occur, the active induction of renewed border cell separation serves to remove infected tissue from the apical meristem area. Plant mutants altered in border cell separation can be used in the future studies to definitively establish the role of border cells in plant health.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectBiology, Cell.en_US
dc.subjectAgriculture, Plant Pathology.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplinePlant Diseasesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorHawes, Martha C.en_US
dc.identifier.proquest9972092en_US
dc.identifier.bibrecord.b40639447en_US
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