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Characterization of avirulence and v...

Lin, Nai-Chun.

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Characterization of avirulence and virulence activities of avrPtoB and its homologs in Pseudomonas syringae.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Characterization of avirulence and virulence activities of avrPtoB and its homologs in Pseudomonas syringae./
作者:	Lin, Nai-Chun.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2004,
面頁冊數:	105 p.
附註:	Source: Dissertations Abstracts International, Volume: 66-02, Section: B.
Contained By:	Dissertations Abstracts International66-02B.
標題:	Plant pathology. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3128249

Characterization of avirulence and virulence activities of avrPtoB and its homologs in Pseudomonas syringae.
Lin, Nai-Chun.

Characterization of avirulence and virulence activities of avrPtoB and its homologs in Pseudomonas syringae. - Ann Arbor : ProQuest Dissertations & Theses, 2004 - 105 p.

Source: Dissertations Abstracts International, Volume: 66-02, Section: B.

Thesis (Ph.D.)--Cornell University, 2004.

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

Bacterial avrirulence (avr) genes were originally defined by their ability to activate defense responses in host plants containing the corresponding resistance (R) genes. Some Avr proteins also have virulence activities, which manifest as increased bacterial growth and more severe disease symptoms in host plants. In the pathosystem of tomato speck disease, resistance to the causal agent Pseudomonas syringae pv. tomato (Pst) is determined by the avirulence genes avrPto or avrPtoB in Pst and the Pto resistance gene in tomato. It was previously shown that mutation of avrPto in Pst DC3000 did not abolish the ability of this strain to trigger Pto-mediated defense responses. In this study, an avrPtoB-deletion mutant, and an avrPto/avrPtoB double mutant were generated using Pst DC3000. Like the avrPto mutant, the avrPtoB-deletion mutant was still able to activate Pto-dependent resistance in tomato. However, the double mutant was no longer recognized by tomato lines expressing Pto. These results indicate that AvrPto and AvrPtoB are the only two effectors in this strain that elicit the Pto-mediated defense responses in tomato and that they have redundant avirulence activity. Interestingly, the Pst DC3000ΔavrPtoΔ avrPtoB mutant caused less severe disease symptoms on susceptible tomato plants and grew to lower levels in Arabidopsis, demonstrating a contribution of both effectors to virulence in Pst DC3000. The avrPtoB gene is highly conserved among different genera of gram-negative phytopathogenic bacteria. Based on the hypothesis that conserved effector genes may play important roles in pathogenesis, five avrPtoB homologs were cloned from representative phytopathogenic bacteria and their activities were investigated. The five AvrPtoB homologs were 37-66% similar at the amino acid level and exhibited similar avirulence and virulence activities when delivered to plant cells by Pst DC3000Δ avrPtoΔavrPtoB. Whether AvrPtoB homologs play the same role in the strains from which they were originally isolated is unknown. However, transcripts and proteins of endogenous avrPtoB homologs were detected in most of the source strains, suggesting that these genes encode open reading frames and may therefore have similar functions in the source strains as avrPtoB does in Pst DC3000.Subjects--Topical Terms:

3174872
Plant pathology.

Characterization of avirulence and virulence activities of avrPtoB and its homologs in Pseudomonas syringae.
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245 1 0 $a Characterization of avirulence and virulence activities of avrPtoB and its homologs in Pseudomonas syringae.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2004
300 $a 105 p.
500 $a Source: Dissertations Abstracts International, Volume: 66-02, Section: B.
500 $a Publisher info.: Dissertation/Thesis.
500 $a Advisor: Martin, Gregory.
502 $a Thesis (Ph.D.)--Cornell University, 2004.
506 $a This item must not be sold to any third party vendors.
506 $a This item must not be added to any third party search indexes.
520 $a Bacterial avrirulence (avr) genes were originally defined by their ability to activate defense responses in host plants containing the corresponding resistance (R) genes. Some Avr proteins also have virulence activities, which manifest as increased bacterial growth and more severe disease symptoms in host plants. In the pathosystem of tomato speck disease, resistance to the causal agent Pseudomonas syringae pv. tomato (Pst) is determined by the avirulence genes avrPto or avrPtoB in Pst and the Pto resistance gene in tomato. It was previously shown that mutation of avrPto in Pst DC3000 did not abolish the ability of this strain to trigger Pto-mediated defense responses. In this study, an avrPtoB-deletion mutant, and an avrPto/avrPtoB double mutant were generated using Pst DC3000. Like the avrPto mutant, the avrPtoB-deletion mutant was still able to activate Pto-dependent resistance in tomato. However, the double mutant was no longer recognized by tomato lines expressing Pto. These results indicate that AvrPto and AvrPtoB are the only two effectors in this strain that elicit the Pto-mediated defense responses in tomato and that they have redundant avirulence activity. Interestingly, the Pst DC3000ΔavrPtoΔ avrPtoB mutant caused less severe disease symptoms on susceptible tomato plants and grew to lower levels in Arabidopsis, demonstrating a contribution of both effectors to virulence in Pst DC3000. The avrPtoB gene is highly conserved among different genera of gram-negative phytopathogenic bacteria. Based on the hypothesis that conserved effector genes may play important roles in pathogenesis, five avrPtoB homologs were cloned from representative phytopathogenic bacteria and their activities were investigated. The five AvrPtoB homologs were 37-66% similar at the amino acid level and exhibited similar avirulence and virulence activities when delivered to plant cells by Pst DC3000Δ avrPtoΔavrPtoB. Whether AvrPtoB homologs play the same role in the strains from which they were originally isolated is unknown. However, transcripts and proteins of endogenous avrPtoB homologs were detected in most of the source strains, suggesting that these genes encode open reading frames and may therefore have similar functions in the source strains as avrPtoB does in Pst DC3000.
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