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From Surviving to Thriving: How Ralstonia solanacearum Mitigates Oxidative Stress in Plant Xylem and Moves through Tubers to New Hosts.

Record Type:	Electronic resources : Monograph/item
Title/Author:	From Surviving to Thriving: How Ralstonia solanacearum Mitigates Oxidative Stress in Plant Xylem and Moves through Tubers to New Hosts./
Author:	Truchon, Alicia N.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2022,
Description:	219 p.
Notes:	Source: Dissertations Abstracts International, Volume: 83-08, Section: B.
Contained By:	Dissertations Abstracts International83-08B.
Subject:	Plant pathology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28965017
ISBN:	9798780632047

From Surviving to Thriving: How Ralstonia solanacearum Mitigates Oxidative Stress in Plant Xylem and Moves through Tubers to New Hosts.
Truchon, Alicia N.

From Surviving to Thriving: How Ralstonia solanacearum Mitigates Oxidative Stress in Plant Xylem and Moves through Tubers to New Hosts. - Ann Arbor : ProQuest Dissertations & Theses, 2022 - 219 p.

Source: Dissertations Abstracts International, Volume: 83-08, Section: B.

Thesis (Ph.D.)--The University of Wisconsin - Madison, 2022.

This item must not be sold to any third party vendors.

Ralstonia solanacearum (Rs) causes bacterial wilt disease on many crops, including banana, geranium, tomato, and brown rot on potatoes. In soil and water, Rs lives as a saprophyte. Rs needs metabolic diversity to take advantage of varying nutrient availability during this saprophytic life stage. However, when this pathogen encounters a plant host, it has adapted to invade plant roots and thrive in the water-transporting xylem vessels. If Rs grows to high cell densities in plants, it forms biofilms that occlude xylem vessels causing wilting symptoms and host collapse and leads Rs to exit roots back to the soil. Rs can also colonize plants to lower bacterial densities, causing asymptomatic latent infections that disseminate the pathogen and complicate disease control measures that depend on detection. While living in the hypoxic, nutrient-limited xylem, Rs depends on inorganic nitrogen metabolism. In this environment, Rs confronts nitrosative stress molecules like nitric oxide (NO) generated by denitrification and host defenses. These molecules damage important cellular machinery, including iron-containing enzymes. NO has often been studied as a signaling molecule and defense response in human-pathogen interactions, but nitrosative stress is understudied in plant-pathogen interactions. This thesis examines how Rs protects its cellular machinery and mitigates nitrosative stress by reducing cellular NO and tightly regulating gene expression. First, I show that Rs deploys NO-induced proteins to minimize the cellular pool of toxic NO. My studies indicate that NorA, NorB, and HmpX interact with NO, are functionally redundant, and are collectively crucial for bacterial fitness in denitrifying conditions, including in tomato plants. I identified a novel NO-induced regulatory mechanism that protects cellular machinery vulnerable to nitrosative stress. In denitrifying conditions and during pathogenesis, the small protein NisR represses the expression of dozens of bacterial functions, most notably iron acquisition. I also studied strategies that Rs has developed to transmit between plant hosts. Andean pandemic lineage (PL) strains of Rs are responsible for a destructive global pandemic of potato brown rot disease. Andean PL strains inflict devastating losses on subsistence and market growers in tropical highlands and are hard to detect in seed tubers from asymptomatic plants. My comparative studies found that PL strains consistently colonize potato tubers. At the same time, Rs strains from Africa also cause potato brown rot very rarely colonized tubers, despite reaching similar population sizes in potato stems. Together with epidemiological data, my evidence suggests that PL Rs strains rapidly displaced the endemic African strains in Madagascar because PL Rs strains are better transmitted in latently infected seed tubers. Finally, I refined and validated a method to detect Rs in geranium stems. Current detection methods for this highly regulated quarantine pest are imperfect. To increase Rs detection efficiency, sensitivity, and specificity in latently infected tissues, I combined and modified aspects of previously developed methods for a more sensitive and larger-scale method to detect PL strains. This new testing protocol was faster and more sensitive in testing infected plant material on a large scale. This method can be adapted to detect Rs on a wide range of samples more efficiently.

ISBN: 9798780632047Subjects--Topical Terms:

3174872
Plant pathology.
Subjects--Index Terms:

Bacterial wilt

From Surviving to Thriving: How Ralstonia solanacearum Mitigates Oxidative Stress in Plant Xylem and Moves through Tubers to New Hosts.
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506 $a This item must not be sold to any third party vendors.
520 $a Ralstonia solanacearum (Rs) causes bacterial wilt disease on many crops, including banana, geranium, tomato, and brown rot on potatoes. In soil and water, Rs lives as a saprophyte. Rs needs metabolic diversity to take advantage of varying nutrient availability during this saprophytic life stage. However, when this pathogen encounters a plant host, it has adapted to invade plant roots and thrive in the water-transporting xylem vessels. If Rs grows to high cell densities in plants, it forms biofilms that occlude xylem vessels causing wilting symptoms and host collapse and leads Rs to exit roots back to the soil. Rs can also colonize plants to lower bacterial densities, causing asymptomatic latent infections that disseminate the pathogen and complicate disease control measures that depend on detection. While living in the hypoxic, nutrient-limited xylem, Rs depends on inorganic nitrogen metabolism. In this environment, Rs confronts nitrosative stress molecules like nitric oxide (NO) generated by denitrification and host defenses. These molecules damage important cellular machinery, including iron-containing enzymes. NO has often been studied as a signaling molecule and defense response in human-pathogen interactions, but nitrosative stress is understudied in plant-pathogen interactions. This thesis examines how Rs protects its cellular machinery and mitigates nitrosative stress by reducing cellular NO and tightly regulating gene expression. First, I show that Rs deploys NO-induced proteins to minimize the cellular pool of toxic NO. My studies indicate that NorA, NorB, and HmpX interact with NO, are functionally redundant, and are collectively crucial for bacterial fitness in denitrifying conditions, including in tomato plants. I identified a novel NO-induced regulatory mechanism that protects cellular machinery vulnerable to nitrosative stress. In denitrifying conditions and during pathogenesis, the small protein NisR represses the expression of dozens of bacterial functions, most notably iron acquisition. I also studied strategies that Rs has developed to transmit between plant hosts. Andean pandemic lineage (PL) strains of Rs are responsible for a destructive global pandemic of potato brown rot disease. Andean PL strains inflict devastating losses on subsistence and market growers in tropical highlands and are hard to detect in seed tubers from asymptomatic plants. My comparative studies found that PL strains consistently colonize potato tubers. At the same time, Rs strains from Africa also cause potato brown rot very rarely colonized tubers, despite reaching similar population sizes in potato stems. Together with epidemiological data, my evidence suggests that PL Rs strains rapidly displaced the endemic African strains in Madagascar because PL Rs strains are better transmitted in latently infected seed tubers. Finally, I refined and validated a method to detect Rs in geranium stems. Current detection methods for this highly regulated quarantine pest are imperfect. To increase Rs detection efficiency, sensitivity, and specificity in latently infected tissues, I combined and modified aspects of previously developed methods for a more sensitive and larger-scale method to detect PL strains. This new testing protocol was faster and more sensitive in testing infected plant material on a large scale. This method can be adapted to detect Rs on a wide range of samples more efficiently.
590 $a School code: 0262.
650 4 $a Plant pathology. $3 3174872
650 4 $a Microbiology. $3 536250
653 $a Bacterial wilt
653 $a Nitric oxide
653 $a Ralstonia solanacearum
653 $a Tuber transmission
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710 2 $a The University of Wisconsin - Madison. $b Microbiology ALS. $3 3183014
773 0 $t Dissertations Abstracts International $g 83-08B.
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791 $a Ph.D.
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793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28965017