Using the Bacterial Plant Pathogen Pseudomonas syringae pv. tomato as a Model to Study the Evolution and Mechanisms of Host Range and Virulence

Most plant pathogens are specialists where only few plant species are susceptible, while all other plants are resistant. Unraveling the mechanisms behind this can thus provide valuable information for breeding or engineering crops with durable disease resistance. A group of Pseudomonas syringae stra...

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Main Author: Yan, Shuangchun
Other Authors: Plant Pathology, Physiology, and Weed Science
Format: Others
Language:en_US
Published: Virginia Tech 2017
Subjects:
Online Access:http://hdl.handle.net/10919/77293
http://scholar.lib.vt.edu/theses/available/etd-12202010-021153/
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spelling ndltd-VTETD-oai-vtechworks.lib.vt.edu-10919-772932020-09-29T05:38:48Z Using the Bacterial Plant Pathogen Pseudomonas syringae pv. tomato as a Model to Study the Evolution and Mechanisms of Host Range and Virulence Yan, Shuangchun Plant Pathology, Physiology, and Weed Science Vinatzer, Boris A. Setubal, João C. Jelesko, John G. Zhang, Liqing Tyler, Brett M. host-microbe interaction callose HopM1 microbial genomics population genetics molecular evolution Arabidopsis thaliana Pseudomonas syringae Most plant pathogens are specialists where only few plant species are susceptible, while all other plants are resistant. Unraveling the mechanisms behind this can thus provide valuable information for breeding or engineering crops with durable disease resistance. A group of Pseudomonas syringae strains with different host ranges while still closely related were thus chosen for comparative study. We confirmed their close phylogenetic relationship. We found evidence supporting that these strains recombined during evolution. The Arabidopsis thaliana and tomato pathogen P. syringae pv. tomato (Pto) DC3000 was found to be an atypical tomato strain, distinct from the typical Pto strains commonly isolated in the field that do not cause disease in A. thaliana, such as Pto T1. Comparing A. thaliana defense responses to DC3000 and T1, we found that T1 is eliciting stronger responses than DC3000. T1 is likely lacking Type III effector genes necessary to suppress plant defense. To test this, we sequenced the genomes of strains that cause and do not cause disease in A. thaliana. Comparative genomics revealed candidate effector genes responsible for this host range difference. Effector genes conserved in strains pathogenic in A. thaliana were expressed in T1 to test whether they would allow T1 to growth better in A. thaliana. Surprisingly, most of them reduced T1 growth. One of the effectors, HopM1, was of particular interest because it is disrupted in typical Pto strains. Although HopM1 has known virulence function in A. thaliana, HopM1 reduced T1 growth in both A. thaliana and tomato. HopM1 also increased the number of bacterial specks but reduced their average size in tomato. Our data suggest that HopM1 can trigger defenses in these plants. Additionally, transgenic detritivore Pseudomonas fluorescens that can secrete HopM1 shows dramatically increased growth in planta. The importance of genetic background of the pathogen for the functions of individual effectors is discussed. T1 cannot be manipulated to become an A. thaliana pathogen by deleting or adding individual genes. We now have a list of genes that can be studied in the future for the molecular basis of host range determination. Ph. D. 2017-04-06T15:44:34Z 2017-04-06T15:44:34Z 2010-12-06 2010-12-20 2016-10-18 2011-01-12 Dissertation Text etd-12202010-021153 http://hdl.handle.net/10919/77293 http://scholar.lib.vt.edu/theses/available/etd-12202010-021153/ en_US In Copyright http://rightsstatements.org/vocab/InC/1.0/ application/pdf application/pdf Virginia Tech
collection NDLTD
language en_US
format Others
sources NDLTD
topic host-microbe interaction
callose
HopM1
microbial genomics
population genetics
molecular evolution
Arabidopsis thaliana
Pseudomonas syringae
spellingShingle host-microbe interaction
callose
HopM1
microbial genomics
population genetics
molecular evolution
Arabidopsis thaliana
Pseudomonas syringae
Yan, Shuangchun
Using the Bacterial Plant Pathogen Pseudomonas syringae pv. tomato as a Model to Study the Evolution and Mechanisms of Host Range and Virulence
description Most plant pathogens are specialists where only few plant species are susceptible, while all other plants are resistant. Unraveling the mechanisms behind this can thus provide valuable information for breeding or engineering crops with durable disease resistance. A group of Pseudomonas syringae strains with different host ranges while still closely related were thus chosen for comparative study. We confirmed their close phylogenetic relationship. We found evidence supporting that these strains recombined during evolution. The Arabidopsis thaliana and tomato pathogen P. syringae pv. tomato (Pto) DC3000 was found to be an atypical tomato strain, distinct from the typical Pto strains commonly isolated in the field that do not cause disease in A. thaliana, such as Pto T1. Comparing A. thaliana defense responses to DC3000 and T1, we found that T1 is eliciting stronger responses than DC3000. T1 is likely lacking Type III effector genes necessary to suppress plant defense. To test this, we sequenced the genomes of strains that cause and do not cause disease in A. thaliana. Comparative genomics revealed candidate effector genes responsible for this host range difference. Effector genes conserved in strains pathogenic in A. thaliana were expressed in T1 to test whether they would allow T1 to growth better in A. thaliana. Surprisingly, most of them reduced T1 growth. One of the effectors, HopM1, was of particular interest because it is disrupted in typical Pto strains. Although HopM1 has known virulence function in A. thaliana, HopM1 reduced T1 growth in both A. thaliana and tomato. HopM1 also increased the number of bacterial specks but reduced their average size in tomato. Our data suggest that HopM1 can trigger defenses in these plants. Additionally, transgenic detritivore Pseudomonas fluorescens that can secrete HopM1 shows dramatically increased growth in planta. The importance of genetic background of the pathogen for the functions of individual effectors is discussed. T1 cannot be manipulated to become an A. thaliana pathogen by deleting or adding individual genes. We now have a list of genes that can be studied in the future for the molecular basis of host range determination. === Ph. D.
author2 Plant Pathology, Physiology, and Weed Science
author_facet Plant Pathology, Physiology, and Weed Science
Yan, Shuangchun
author Yan, Shuangchun
author_sort Yan, Shuangchun
title Using the Bacterial Plant Pathogen Pseudomonas syringae pv. tomato as a Model to Study the Evolution and Mechanisms of Host Range and Virulence
title_short Using the Bacterial Plant Pathogen Pseudomonas syringae pv. tomato as a Model to Study the Evolution and Mechanisms of Host Range and Virulence
title_full Using the Bacterial Plant Pathogen Pseudomonas syringae pv. tomato as a Model to Study the Evolution and Mechanisms of Host Range and Virulence
title_fullStr Using the Bacterial Plant Pathogen Pseudomonas syringae pv. tomato as a Model to Study the Evolution and Mechanisms of Host Range and Virulence
title_full_unstemmed Using the Bacterial Plant Pathogen Pseudomonas syringae pv. tomato as a Model to Study the Evolution and Mechanisms of Host Range and Virulence
title_sort using the bacterial plant pathogen pseudomonas syringae pv. tomato as a model to study the evolution and mechanisms of host range and virulence
publisher Virginia Tech
publishDate 2017
url http://hdl.handle.net/10919/77293
http://scholar.lib.vt.edu/theses/available/etd-12202010-021153/
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